Adding upstream version 1.20.14.upstream/1.20.14upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

249 files changed, 17373 insertions, 0 deletions

diff --git a/src/internal/types/testdata/check/blank.go b/src/internal/types/testdata/check/blank.go
new file mode 100644
index 0000000..6a2507f
--- /dev/null
+++ b/src/internal/types/testdata/check/blank.go
@@ -0,0 +1,5 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package _ /* ERROR invalid package name */
diff --git a/src/internal/types/testdata/check/builtins0.go b/src/internal/types/testdata/check/builtins0.go
new file mode 100644
index 0000000..308f70b
--- /dev/null
+++ b/src/internal/types/testdata/check/builtins0.go
@@ -0,0 +1,967 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// builtin calls
+
+package builtins
+
+import "unsafe"
+
+func f0() {}
+
+func append1() {
+	var b byte
+	var x int
+	var s []byte
+	_ = append() // ERROR not enough arguments
+	_ = append("foo" /* ERROR must be a slice */ )
+	_ = append(nil /* ERROR must be a slice */ , s)
+	_ = append(x /* ERROR must be a slice */ , s)
+	_ = append(s)
+	_ = append(s, nil...)
+	append /* ERROR not used */ (s)
+
+	_ = append(s, b)
+	_ = append(s, x /* ERROR cannot use x */ )
+	_ = append(s, s /* ERROR cannot use s */ )
+	_ = append(s...) /* ERROR not enough arguments */
+	_ = append(s, b, s /* ERROR too many arguments */ ...)
+	_ = append(s, 1, 2, 3)
+	_ = append(s, 1, 2, 3, x /* ERROR cannot use x */ , 5, 6, 6)
+	_ = append(s, 1, 2 /* ERROR too many arguments */, s...)
+	_ = append([]interface{}(nil), 1, 2, "foo", x, 3.1425, false)
+
+	type S []byte
+	type T string
+	var t T
+	_ = append(s, "foo" /* ERROR cannot use .* in argument to append */ )
+	_ = append(s, "foo"...)
+	_ = append(S(s), "foo" /* ERROR cannot use .* in argument to append */ )
+	_ = append(S(s), "foo"...)
+	_ = append(s, t /* ERROR cannot use t */ )
+	_ = append(s, t...)
+	_ = append(s, T("foo")...)
+	_ = append(S(s), t /* ERROR cannot use t */ )
+	_ = append(S(s), t...)
+	_ = append(S(s), T("foo")...)
+	_ = append([]string{}, t /* ERROR cannot use t */ , "foo")
+	_ = append([]T{}, t, "foo")
+}
+
+// from the spec
+func append2() {
+	s0 := []int{0, 0}
+	s1 := append(s0, 2)                // append a single element     s1 == []int{0, 0, 2}
+	s2 := append(s1, 3, 5, 7)          // append multiple elements    s2 == []int{0, 0, 2, 3, 5, 7}
+	s3 := append(s2, s0...)            // append a slice              s3 == []int{0, 0, 2, 3, 5, 7, 0, 0}
+	s4 := append(s3[3:6], s3[2:]...)   // append overlapping slice    s4 == []int{3, 5, 7, 2, 3, 5, 7, 0, 0}
+
+	var t []interface{}
+	t = append(t, 42, 3.1415, "foo")   //                             t == []interface{}{42, 3.1415, "foo"}
+
+	var b []byte
+	b = append(b, "bar"...)            // append string contents      b == []byte{'b', 'a', 'r' }
+
+	_ = s4
+}
+
+func append3() {
+	f1 := func() (s []int) { return }
+	f2 := func() (s []int, x int) { return }
+	f3 := func() (s []int, x, y int) { return }
+	f5 := func() (s []interface{}, x int, y float32, z string, b bool) { return }
+	ff := func() (int, float32) { return 0, 0 }
+	_ = append(f0 /* ERROR used as value */ ())
+	_ = append(f1())
+	_ = append(f2())
+	_ = append(f3())
+	_ = append(f5())
+	_ = append(ff /* ERROR must be a slice */ ()) // TODO(gri) better error message
+}
+
+func cap1() {
+	var a [10]bool
+	var p *[20]int
+	var c chan string
+	_ = cap() // ERROR not enough arguments
+	_ = cap(1, 2) // ERROR too many arguments
+	_ = cap(42 /* ERROR invalid */)
+	const _3 = cap(a)
+	assert(_3 == 10)
+	const _4 = cap(p)
+	assert(_4 == 20)
+	_ = cap(c)
+	cap /* ERROR not used */ (c)
+
+	// issue 4744
+	type T struct{ a [10]int }
+	const _ = cap(((*T)(nil)).a)
+
+	var s [][]byte
+	_ = cap(s)
+	_ = cap(s... /* ERROR invalid use of \.\.\. */ )
+}
+
+func cap2() {
+	f1a := func() (a [10]int) { return }
+	f1s := func() (s []int) { return }
+	f2 := func() (s []int, x int) { return }
+	_ = cap(f0 /* ERROR used as value */ ())
+	_ = cap(f1a())
+	_ = cap(f1s())
+	_ = cap(f2()) // ERROR too many arguments
+}
+
+// test cases for issue 7387
+func cap3() {
+	var f = func() int { return 0 }
+	var x = f()
+	const (
+		_ = cap([4]int{})
+		_ = cap([4]int{x})
+		_ = cap /* ERROR not constant */ ([4]int{f()})
+		_ = cap /* ERROR not constant */ ([4]int{cap([]int{})})
+		_ = cap([4]int{cap([4]int{})})
+	)
+	var y float64
+	var z complex128
+	const (
+		_ = cap([4]float64{})
+		_ = cap([4]float64{y})
+		_ = cap([4]float64{real(2i)})
+		_ = cap /* ERROR not constant */ ([4]float64{real(z)})
+	)
+	var ch chan [10]int
+	const (
+		_ = cap /* ERROR not constant */ (<-ch)
+		_ = cap /* ERROR not constant */ ([4]int{(<-ch)[0]})
+	)
+}
+
+func clear1() {
+	var a [10]int
+	var m map[float64]string
+	var s []byte
+	clear(a /* ERROR cannot clear a */)
+	clear(&a)
+	clear(m)
+	clear(s)
+	clear([]int{})
+}
+
+func close1() {
+	var c chan int
+	var r <-chan int
+	close() // ERROR not enough arguments
+	close(1, 2) // ERROR too many arguments
+	close(42 /* ERROR cannot close non-channel */)
+	close(r /* ERROR receive-only channel */)
+	close(c)
+	_ = close /* ERROR used as value */ (c)
+
+	var s []chan int
+	close(s... /* ERROR invalid use of \.\.\. */ )
+}
+
+func close2() {
+	f1 := func() (ch chan int) { return }
+	f2 := func() (ch chan int, x int) { return }
+	close(f0 /* ERROR used as value */ ())
+	close(f1())
+	close(f2()) // ERROR too many arguments
+}
+
+func complex1() {
+	var i32 int32
+	var f32 float32
+	var f64 float64
+	var c64 complex64
+	var c128 complex128
+	_ = complex() // ERROR not enough arguments
+	_ = complex(1) // ERROR not enough arguments
+	_ = complex(true /* ERROR mismatched types */ , 0)
+	_ = complex(i32 /* ERROR expected floating-point */ , 0)
+	_ = complex("foo" /* ERROR mismatched types */ , 0)
+	_ = complex(c64 /* ERROR expected floating-point */ , 0)
+	_ = complex(0 /* ERROR mismatched types */ , true)
+	_ = complex(0 /* ERROR expected floating-point */ , i32)
+	_ = complex(0 /* ERROR mismatched types */ , "foo")
+	_ = complex(0 /* ERROR expected floating-point */ , c64)
+	_ = complex(f32, f32)
+	_ = complex(f32, 1)
+	_ = complex(f32, 1.0)
+	_ = complex(f32, 'a')
+	_ = complex(f64, f64)
+	_ = complex(f64, 1)
+	_ = complex(f64, 1.0)
+	_ = complex(f64, 'a')
+	_ = complex(f32 /* ERROR mismatched types */ , f64)
+	_ = complex(f64 /* ERROR mismatched types */ , f32)
+	_ = complex(1, 1)
+	_ = complex(1, 1.1)
+	_ = complex(1, 'a')
+	complex /* ERROR not used */ (1, 2)
+
+	var _ complex64 = complex(f32, f32)
+	var _ complex64 = complex /* ERROR cannot use .* in variable declaration */ (f64, f64)
+
+	var _ complex128 = complex /* ERROR cannot use .* in variable declaration */ (f32, f32)
+	var _ complex128 = complex(f64, f64)
+
+	// untyped constants
+	const _ int = complex(1, 0)
+	const _ float32 = complex(1, 0)
+	const _ complex64 = complex(1, 0)
+	const _ complex128 = complex(1, 0)
+	const _ = complex(0i, 0i)
+	const _ = complex(0i, 0)
+	const _ int = 1.0 + complex(1, 0i)
+
+	const _ int = complex /* ERROR int */ (1.1, 0)
+	const _ float32 = complex /* ERROR float32 */ (1, 2)
+
+	// untyped values
+	var s uint
+	_ = complex(1 /* ERROR integer */ <<s, 0)
+	const _ = complex /* ERROR not constant */ (1 /* ERROR integer */ <<s, 0)
+	var _ int = complex /* ERROR cannot use .* in variable declaration */ (1 /* ERROR integer */ <<s, 0)
+
+	// floating-point argument types must be identical
+	type F32 float32
+	type F64 float64
+	var x32 F32
+	var x64 F64
+	c64 = complex(x32, x32)
+	_ = complex(x32 /* ERROR mismatched types */ , f32)
+	_ = complex(f32 /* ERROR mismatched types */ , x32)
+	c128 = complex(x64, x64)
+	_ = c128
+	_ = complex(x64 /* ERROR mismatched types */ , f64)
+	_ = complex(f64 /* ERROR mismatched types */ , x64)
+
+	var t []float32
+	_ = complex(t... /* ERROR invalid use of \.\.\. */ )
+}
+
+func complex2() {
+	f1 := func() (x float32) { return }
+	f2 := func() (x, y float32) { return }
+	f3 := func() (x, y, z float32) { return }
+	_ = complex(f0 /* ERROR used as value */ ())
+	_ = complex(f1()) // ERROR not enough arguments
+	_ = complex(f2())
+	_ = complex(f3()) // ERROR too many arguments
+}
+
+func copy1() {
+	copy() // ERROR not enough arguments
+	copy("foo") // ERROR not enough arguments
+	copy([ /* ERROR copy expects slice arguments */ ...]int{}, []int{})
+	copy([ /* ERROR copy expects slice arguments */ ]int{}, [...]int{})
+	copy([ /* ERROR different element types */ ]int8{}, "foo")
+
+	// spec examples
+	var a = [...]int{0, 1, 2, 3, 4, 5, 6, 7}
+	var s = make([]int, 6)
+	var b = make([]byte, 5)
+	n1 := copy(s, a[0:])            // n1 == 6, s == []int{0, 1, 2, 3, 4, 5}
+	n2 := copy(s, s[2:])            // n2 == 4, s == []int{2, 3, 4, 5, 4, 5}
+	n3 := copy(b, "Hello, World!")  // n3 == 5, b == []byte("Hello")
+	_, _, _ = n1, n2, n3
+
+	var t [][]int
+	copy(t, t)
+	copy(t /* ERROR copy expects slice arguments */ , nil)
+	copy(nil /* ERROR copy expects slice arguments */ , t)
+	copy(nil /* ERROR copy expects slice arguments */ , nil)
+	copy(t... /* ERROR invalid use of \.\.\. */ )
+}
+
+func copy2() {
+	f1 := func() (a []int) { return }
+	f2 := func() (a, b []int) { return }
+	f3 := func() (a, b, c []int) { return }
+	copy(f0 /* ERROR used as value */ ())
+	copy(f1()) // ERROR not enough arguments
+	copy(f2())
+	copy(f3()) // ERROR too many arguments
+}
+
+func delete1() {
+	var m map[string]int
+	var s string
+	delete() // ERROR not enough arguments
+	delete(1) // ERROR not enough arguments
+	delete(1, 2, 3) // ERROR too many arguments
+	delete(m, 0 /* ERROR cannot use */)
+	delete(m, s)
+	_ = delete /* ERROR used as value */ (m, s)
+
+	var t []map[string]string
+	delete(t... /* ERROR invalid use of \.\.\. */ )
+}
+
+func delete2() {
+	f1 := func() (m map[string]int) { return }
+	f2 := func() (m map[string]int, k string) { return }
+	f3 := func() (m map[string]int, k string, x float32) { return }
+	delete(f0 /* ERROR used as value */ ())
+	delete(f1()) // ERROR not enough arguments
+	delete(f2())
+	delete(f3()) // ERROR too many arguments
+}
+
+func imag1() {
+	var f32 float32
+	var f64 float64
+	var c64 complex64
+	var c128 complex128
+	_ = imag() // ERROR not enough arguments
+	_ = imag(1, 2) // ERROR too many arguments
+	_ = imag(10)
+	_ = imag(2.7182818)
+	_ = imag("foo" /* ERROR expected complex */)
+	_ = imag('a')
+	const _5 = imag(1 + 2i)
+	assert(_5 == 2)
+	f32 = _5
+	f64 = _5
+	const _6 = imag(0i)
+	assert(_6 == 0)
+	f32 = imag(c64)
+	f64 = imag(c128)
+	f32 = imag /* ERROR cannot use .* in assignment */ (c128)
+	f64 = imag /* ERROR cannot use .* in assignment */ (c64)
+	imag /* ERROR not used */ (c64)
+	_, _ = f32, f64
+
+	// complex type may not be predeclared
+	type C64 complex64
+	type C128 complex128
+	var x64 C64
+	var x128 C128
+	f32 = imag(x64)
+	f64 = imag(x128)
+
+	var a []complex64
+	_ = imag(a... /* ERROR invalid use of \.\.\. */ )
+
+	// if argument is untyped, result is untyped
+	const _ byte = imag(1.2 + 3i)
+	const _ complex128 = imag(1.2 + 3i)
+
+	// lhs constant shift operands are typed as complex128
+	var s uint
+	_ = imag(1 /* ERROR must be integer */ << s)
+}
+
+func imag2() {
+	f1 := func() (x complex128) { return }
+	f2 := func() (x, y complex128) { return }
+	_ = imag(f0 /* ERROR used as value */ ())
+	_ = imag(f1())
+	_ = imag(f2()) // ERROR too many arguments
+}
+
+func len1() {
+	const c = "foobar"
+	var a [10]bool
+	var p *[20]int
+	var m map[string]complex128
+	_ = len() // ERROR not enough arguments
+	_ = len(1, 2) // ERROR too many arguments
+	_ = len(42 /* ERROR invalid */)
+	const _3 = len(c)
+	assert(_3 == 6)
+	const _4 = len(a)
+	assert(_4 == 10)
+	const _5 = len(p)
+	assert(_5 == 20)
+	_ = len(m)
+	len /* ERROR not used */ (c)
+
+	// esoteric case
+	var t string
+	var hash map[interface{}][]*[10]int
+	const n = len /* ERROR not constant */ (hash[recover()][len(t)])
+	assert(n == 10) // ok because n has unknown value and no error is reported
+	var ch <-chan int
+	const nn = len /* ERROR not constant */ (hash[<-ch][len(t)])
+
+	// issue 4744
+	type T struct{ a [10]int }
+	const _ = len(((*T)(nil)).a)
+
+	var s [][]byte
+	_ = len(s)
+	_ = len(s... /* ERROR invalid use of \.\.\. */ )
+}
+
+func len2() {
+	f1 := func() (x []int) { return }
+	f2 := func() (x, y []int) { return }
+	_ = len(f0 /* ERROR used as value */ ())
+	_ = len(f1())
+	_ = len(f2()) // ERROR too many arguments
+}
+
+// test cases for issue 7387
+func len3() {
+	var f = func() int { return 0 }
+	var x = f()
+	const (
+		_ = len([4]int{})
+		_ = len([4]int{x})
+		_ = len /* ERROR not constant */ ([4]int{f()})
+		_ = len /* ERROR not constant */ ([4]int{len([]int{})})
+		_ = len([4]int{len([4]int{})})
+	)
+	var y float64
+	var z complex128
+	const (
+		_ = len([4]float64{})
+		_ = len([4]float64{y})
+		_ = len([4]float64{real(2i)})
+		_ = len /* ERROR not constant */ ([4]float64{real(z)})
+	)
+	var ch chan [10]int
+	const (
+		_ = len /* ERROR not constant */ (<-ch)
+		_ = len /* ERROR not constant */ ([4]int{(<-ch)[0]})
+	)
+}
+
+func make1() {
+	var n int
+	var m float32
+	var s uint
+
+	_ = make() // ERROR not enough arguments
+	_ = make(1 /* ERROR not a type */)
+	_ = make(int /* ERROR cannot make */)
+
+	// slices
+	_ = make/* ERROR arguments */ ([]int)
+	_ = make/* ERROR arguments */ ([]int, 2, 3, 4)
+	_ = make([]int, int /* ERROR not an expression */)
+	_ = make([]int, 10, float32 /* ERROR not an expression */)
+	_ = make([]int, "foo" /* ERROR cannot convert */)
+	_ = make([]int, 10, 2.3 /* ERROR truncated */)
+	_ = make([]int, 5, 10.0)
+	_ = make([]int, 0i)
+	_ = make([]int, 1.0)
+	_ = make([]int, 1.0<<s)
+	_ = make([]int, 1.1 /* ERROR int */ <<s)
+	_ = make([]int, - /* ERROR must not be negative */ 1, 10)
+	_ = make([]int, 0, - /* ERROR must not be negative */ 1)
+	_ = make([]int, - /* ERROR must not be negative */ 1, - /* ERROR must not be negative */ 1)
+	_ = make([]int, 1 /* ERROR overflows */ <<100, 1 /* ERROR overflows */ <<100)
+	_ = make([]int, 10 /* ERROR length and capacity swapped */ , 9)
+	_ = make([]int, 1 /* ERROR overflows */ <<100, 12345)
+	_ = make([]int, m /* ERROR must be integer */ )
+        _ = &make /* ERROR cannot take address */ ([]int, 0)
+
+	// maps
+	_ = make /* ERROR arguments */ (map[int]string, 10, 20)
+	_ = make(map[int]float32, int /* ERROR not an expression */)
+	_ = make(map[int]float32, "foo" /* ERROR cannot convert */)
+	_ = make(map[int]float32, 10)
+	_ = make(map[int]float32, n)
+	_ = make(map[int]float32, int64(n))
+	_ = make(map[string]bool, 10.0)
+	_ = make(map[string]bool, 10.0<<s)
+        _ = &make /* ERROR cannot take address */ (map[string]bool)
+
+	// channels
+	_ = make /* ERROR arguments */ (chan int, 10, 20)
+	_ = make(chan int, int /* ERROR not an expression */)
+	_ = make(chan<- int, "foo" /* ERROR cannot convert */)
+	_ = make(chan int, - /* ERROR must not be negative */ 10)
+	_ = make(<-chan float64, 10)
+	_ = make(chan chan int, n)
+	_ = make(chan string, int64(n))
+	_ = make(chan bool, 10.0)
+	_ = make(chan bool, 10.0<<s)
+        _ = &make /* ERROR cannot take address */ (chan bool)
+
+	make /* ERROR not used */ ([]int, 10)
+
+	var t []int
+	_ = make([]int, t[0], t[1])
+	_ = make([]int, t... /* ERROR invalid use of \.\.\. */ )
+}
+
+func make2() {
+	f1 := func() (x []int) { return }
+	_ = make(f0 /* ERROR not a type */ ())
+	_ = make(f1 /* ERROR not a type */ ())
+}
+
+func new1() {
+	_ = new() // ERROR not enough arguments
+	_ = new(1, 2) // ERROR too many arguments
+	_ = new("foo" /* ERROR not a type */)
+	p := new(float64)
+	_ = new(struct{ x, y int })
+	q := new(*float64)
+	_ = *p == **q
+	new /* ERROR not used */ (int)
+        _ = &new /* ERROR cannot take address */ (int)
+
+	_ = new(int... /* ERROR invalid use of \.\.\. */ )
+}
+
+func new2() {
+	f1 := func() (x []int) { return }
+	_ = new(f0 /* ERROR not a type */ ())
+	_ = new(f1 /* ERROR not a type */ ())
+}
+
+func panic1() {
+	panic() // ERROR not enough arguments
+	panic(1, 2) // ERROR too many arguments
+	panic(0)
+	panic("foo")
+	panic(false)
+	panic(1<<10)
+	panic(1 << /* ERROR constant shift overflow */ 1000)
+	_ = panic /* ERROR used as value */ (0)
+
+	var s []byte
+	panic(s)
+	panic(s... /* ERROR invalid use of \.\.\. */ )
+}
+
+func panic2() {
+	f1 := func() (x int) { return }
+	f2 := func() (x, y int) { return }
+	panic(f0 /* ERROR used as value */ ())
+	panic(f1())
+	panic(f2()) // ERROR too many arguments
+}
+
+func print1() {
+	print()
+	print(1)
+	print(1, 2)
+	print("foo")
+	print(2.718281828)
+	print(false)
+	print(1<<10)
+	print(1 << /* ERROR constant shift overflow */ 1000)
+	println(nil /* ERROR untyped nil */ )
+
+	var s []int
+	print(s... /* ERROR invalid use of \.\.\. */ )
+	_ = print /* ERROR used as value */ ()
+}
+
+func print2() {
+	f1 := func() (x int) { return }
+	f2 := func() (x, y int) { return }
+	f3 := func() (x int, y float32, z string) { return }
+	print(f0 /* ERROR used as value */ ())
+	print(f1())
+	print(f2())
+	print(f3())
+}
+
+func println1() {
+	println()
+	println(1)
+	println(1, 2)
+	println("foo")
+	println(2.718281828)
+	println(false)
+	println(1<<10)
+	println(1 << /* ERROR constant shift overflow */ 1000)
+	println(nil /* ERROR untyped nil */ )
+
+	var s []int
+	println(s... /* ERROR invalid use of \.\.\. */ )
+	_ = println /* ERROR used as value */ ()
+}
+
+func println2() {
+	f1 := func() (x int) { return }
+	f2 := func() (x, y int) { return }
+	f3 := func() (x int, y float32, z string) { return }
+	println(f0 /* ERROR used as value */ ())
+	println(f1())
+	println(f2())
+	println(f3())
+}
+
+func real1() {
+	var f32 float32
+	var f64 float64
+	var c64 complex64
+	var c128 complex128
+	_ = real() // ERROR not enough arguments
+	_ = real(1, 2) // ERROR too many arguments
+	_ = real(10)
+	_ = real(2.7182818)
+	_ = real("foo" /* ERROR expected complex */)
+	const _5 = real(1 + 2i)
+	assert(_5 == 1)
+	f32 = _5
+	f64 = _5
+	const _6 = real(0i)
+	assert(_6 == 0)
+	f32 = real(c64)
+	f64 = real(c128)
+	f32 = real /* ERROR cannot use .* in assignment */ (c128)
+	f64 = real /* ERROR cannot use .* in assignment */ (c64)
+	real /* ERROR not used */ (c64)
+
+	// complex type may not be predeclared
+	type C64 complex64
+	type C128 complex128
+	var x64 C64
+	var x128 C128
+	f32 = imag(x64)
+	f64 = imag(x128)
+	_, _ = f32, f64
+
+	var a []complex64
+	_ = real(a... /* ERROR invalid use of \.\.\. */ )
+
+	// if argument is untyped, result is untyped
+	const _ byte = real(1 + 2.3i)
+	const _ complex128 = real(1 + 2.3i)
+
+	// lhs constant shift operands are typed as complex128
+	var s uint
+	_ = real(1 /* ERROR must be integer */ << s)
+}
+
+func real2() {
+	f1 := func() (x complex128) { return }
+	f2 := func() (x, y complex128) { return }
+	_ = real(f0 /* ERROR used as value */ ())
+	_ = real(f1())
+	_ = real(f2()) // ERROR too many arguments
+}
+
+func recover1() {
+	_ = recover()
+	_ = recover(10) // ERROR too many arguments
+	recover()
+
+	var s []int
+	recover(s... /* ERROR invalid use of \.\.\. */ )
+}
+
+func recover2() {
+	f1 := func() (x int) { return }
+	f2 := func() (x, y int) { return }
+	_ = recover(f0 /* ERROR used as value */ ())
+	_ = recover(f1()) // ERROR too many arguments
+	_ = recover(f2()) // ERROR too many arguments
+}
+
+// assuming types.DefaultPtrSize == 8
+type S0 struct{      // offset
+	a bool       //  0
+	b rune       //  4
+	c *int       //  8
+	d bool       // 16
+	e complex128 // 24
+}                    // 40
+
+type S1 struct{   // offset
+	x float32 //  0
+	y string  //  8
+	z *S1     // 24
+	S0        // 32
+}                 // 72
+
+type S2 struct{ // offset
+	*S1     //  0
+}               //  8
+
+type S3 struct { // offset
+	a int64  //  0
+	b int32  //  8
+}                // 12
+
+type S4 struct { // offset
+	S3       //  0
+	int32    // 12
+}                // 16
+
+type S5 struct {   // offset
+	a [3]int32 //  0
+	b int32    // 12
+}                  // 16
+
+func (S2) m() {}
+
+func Alignof1() {
+	var x int
+	_ = unsafe.Alignof() // ERROR not enough arguments
+	_ = unsafe.Alignof(1, 2) // ERROR too many arguments
+	_ = unsafe.Alignof(int /* ERROR not an expression */)
+	_ = unsafe.Alignof(42)
+	_ = unsafe.Alignof(new(struct{}))
+	_ = unsafe.Alignof(1<<10)
+	_ = unsafe.Alignof(1 << /* ERROR constant shift overflow */ 1000)
+	_ = unsafe.Alignof(nil /* ERROR "untyped nil */ )
+	unsafe /* ERROR not used */ .Alignof(x)
+
+	var y S0
+	assert(unsafe.Alignof(y.a) == 1)
+	assert(unsafe.Alignof(y.b) == 4)
+	assert(unsafe.Alignof(y.c) == 8)
+	assert(unsafe.Alignof(y.d) == 1)
+	assert(unsafe.Alignof(y.e) == 8)
+
+	var s []byte
+	_ = unsafe.Alignof(s)
+	_ = unsafe.Alignof(s... /* ERROR invalid use of \.\.\. */ )
+}
+
+func Alignof2() {
+	f1 := func() (x int32) { return }
+	f2 := func() (x, y int32) { return }
+	_ = unsafe.Alignof(f0 /* ERROR used as value */ ())
+	assert(unsafe.Alignof(f1()) == 4)
+	_ = unsafe.Alignof(f2()) // ERROR too many arguments
+}
+
+func Offsetof1() {
+	var x struct{ f int }
+	_ = unsafe.Offsetof() // ERROR not enough arguments
+	_ = unsafe.Offsetof(1, 2) // ERROR too many arguments
+	_ = unsafe.Offsetof(int /* ERROR not a selector expression */ )
+	_ = unsafe.Offsetof(x /* ERROR not a selector expression */ )
+	_ = unsafe.Offsetof(nil /* ERROR not a selector expression */ )
+	_ = unsafe.Offsetof(x.f)
+	_ = unsafe.Offsetof((x.f))
+	_ = unsafe.Offsetof((((((((x))).f)))))
+	unsafe /* ERROR not used */ .Offsetof(x.f)
+
+	var y0 S0
+	assert(unsafe.Offsetof(y0.a) == 0)
+	assert(unsafe.Offsetof(y0.b) == 4)
+	assert(unsafe.Offsetof(y0.c) == 8)
+	assert(unsafe.Offsetof(y0.d) == 16)
+	assert(unsafe.Offsetof(y0.e) == 24)
+
+	var y1 S1
+	assert(unsafe.Offsetof(y1.x) == 0)
+	assert(unsafe.Offsetof(y1.y) == 8)
+	assert(unsafe.Offsetof(y1.z) == 24)
+	assert(unsafe.Offsetof(y1.S0) == 32)
+
+	assert(unsafe.Offsetof(y1.S0.a) == 0) // relative to S0
+	assert(unsafe.Offsetof(y1.a) == 32)   // relative to S1
+	assert(unsafe.Offsetof(y1.b) == 36)   // relative to S1
+	assert(unsafe.Offsetof(y1.c) == 40)   // relative to S1
+	assert(unsafe.Offsetof(y1.d) == 48)   // relative to S1
+	assert(unsafe.Offsetof(y1.e) == 56)   // relative to S1
+
+	var y1p *S1
+	assert(unsafe.Offsetof(y1p.S0) == 32)
+
+	type P *S1
+	var p P = y1p
+	assert(unsafe.Offsetof(p.S0) == 32)
+
+	var y2 S2
+	assert(unsafe.Offsetof(y2.S1) == 0)
+	_ = unsafe.Offsetof(y2 /* ERROR embedded via a pointer */ .x)
+	_ = unsafe.Offsetof(y2 /* ERROR method value */ .m)
+
+	var s []byte
+	_ = unsafe.Offsetof(s... /* ERROR invalid use of \.\.\. */ )
+}
+
+func Offsetof2() {
+	f1 := func() (x int32) { return }
+	f2 := func() (x, y int32) { return }
+	_ = unsafe.Offsetof(f0 /* ERROR not a selector expression */ ())
+	_ = unsafe.Offsetof(f1 /* ERROR not a selector expression */ ())
+	_ = unsafe.Offsetof(f2 /* ERROR not a selector expression */ ())
+}
+
+func Sizeof1() {
+	var x int
+	_ = unsafe.Sizeof() // ERROR not enough arguments
+	_ = unsafe.Sizeof(1, 2) // ERROR too many arguments
+	_ = unsafe.Sizeof(int /* ERROR not an expression */)
+	_ = unsafe.Sizeof(42)
+	_ = unsafe.Sizeof(new(complex128))
+	_ = unsafe.Sizeof(1<<10)
+	_ = unsafe.Sizeof(1 << /* ERROR constant shift overflow */ 1000)
+	_ = unsafe.Sizeof(nil /* ERROR untyped nil */ )
+	unsafe /* ERROR not used */ .Sizeof(x)
+
+	// basic types have size guarantees
+	assert(unsafe.Sizeof(byte(0)) == 1)
+	assert(unsafe.Sizeof(uint8(0)) == 1)
+	assert(unsafe.Sizeof(int8(0)) == 1)
+	assert(unsafe.Sizeof(uint16(0)) == 2)
+	assert(unsafe.Sizeof(int16(0)) == 2)
+	assert(unsafe.Sizeof(uint32(0)) == 4)
+	assert(unsafe.Sizeof(int32(0)) == 4)
+	assert(unsafe.Sizeof(float32(0)) == 4)
+	assert(unsafe.Sizeof(uint64(0)) == 8)
+	assert(unsafe.Sizeof(int64(0)) == 8)
+	assert(unsafe.Sizeof(float64(0)) == 8)
+	assert(unsafe.Sizeof(complex64(0)) == 8)
+	assert(unsafe.Sizeof(complex128(0)) == 16)
+
+	var y0 S0
+	assert(unsafe.Sizeof(y0.a) == 1)
+	assert(unsafe.Sizeof(y0.b) == 4)
+	assert(unsafe.Sizeof(y0.c) == 8)
+	assert(unsafe.Sizeof(y0.d) == 1)
+	assert(unsafe.Sizeof(y0.e) == 16)
+	assert(unsafe.Sizeof(y0) == 40)
+
+	var y1 S1
+	assert(unsafe.Sizeof(y1) == 72)
+
+	var y2 S2
+	assert(unsafe.Sizeof(y2) == 8)
+
+	var y3 S3
+	assert(unsafe.Sizeof(y3) == 12)
+
+	var y4 S4
+	assert(unsafe.Sizeof(y4) == 16)
+
+	var y5 S5
+	assert(unsafe.Sizeof(y5) == 16)
+
+	var a3 [10]S3
+	assert(unsafe.Sizeof(a3) == 156)
+
+	// test case for issue 5670
+	type T struct {
+		a int32
+		_ int32
+		c int32
+	}
+	assert(unsafe.Sizeof(T{}) == 12)
+
+	var s []byte
+	_ = unsafe.Sizeof(s)
+	_ = unsafe.Sizeof(s... /* ERROR invalid use of \.\.\. */ )
+}
+
+func Sizeof2() {
+	f1 := func() (x int64) { return }
+	f2 := func() (x, y int64) { return }
+	_ = unsafe.Sizeof(f0 /* ERROR used as value */ ())
+	assert(unsafe.Sizeof(f1()) == 8)
+	_ = unsafe.Sizeof(f2()) // ERROR too many arguments
+}
+
+func Slice1() {
+	var x int
+	unsafe.Slice()        // ERROR not enough arguments
+	unsafe.Slice(1, 2, 3) // ERROR too many arguments
+	unsafe.Slice(1 /* ERROR is not a pointer */ , 2)
+	unsafe.Slice(nil /* ERROR nil is not a pointer */ , 0)
+	unsafe.Slice(&x, "foo" /* ERROR cannot convert .* to type int */ )
+	unsafe.Slice(&x, 1.2 /* ERROR truncated to int */ )
+	unsafe.Slice(&x, - /* ERROR must not be negative */ 1)
+	unsafe /* ERROR not used */ .Slice(&x, 0)
+	var _ []byte = unsafe /* ERROR value of type \[\]int */ .Slice(&x, 0)
+
+	var _ []int = unsafe.Slice(&x, 0)
+	_ = unsafe.Slice(&x, 1.0)
+	_ = unsafe.Slice((*int)(nil), 0)
+}
+
+func SliceData1() {
+	var s []int
+	unsafe.SliceData(0 /* ERROR not a slice */)
+	unsafe /* ERROR not used */ .SliceData(s)
+
+	type S []int
+	_ = unsafe.SliceData(s)
+	_ = unsafe.SliceData(S{})
+}
+
+func String1() {
+	var b byte
+	unsafe.String()        // ERROR not enough arguments
+	unsafe.String(1, 2, 3) // ERROR too many arguments
+	unsafe.String(1 /* ERROR cannot use 1 */ , 2)
+	unsafe.String(&b, "foo" /* ERROR cannot convert .* to type int */ )
+	unsafe.String(&b, 1.2 /* ERROR truncated to int */ )
+	unsafe.String(&b, - /* ERROR must not be negative */ 1)
+	unsafe /* ERROR not used */ .String(&b, 0)
+	var _ []byte = unsafe /* ERROR value of type string */ .String(&b, 0)
+
+	var _ string = unsafe.String(&b, 0)
+	_ = unsafe.String(&b, 1.0)
+	_ = unsafe.String(nil, 0) // here we allow nil as ptr argument (in contrast to unsafe.Slice)
+}
+
+func StringData1() {
+	var s string
+	type S string
+	unsafe.StringData(0 /* ERROR cannot use 0 */)
+	unsafe.StringData(S /* ERROR cannot use S */ ("foo"))
+	unsafe /* ERROR not used */ .StringData(s)
+
+	_ = unsafe.StringData(s)
+	_ = unsafe.StringData("foo")
+}
+
+// self-testing only
+func assert1() {
+	var x int
+	assert() /* ERROR not enough arguments */
+	assert(1, 2) /* ERROR too many arguments */
+	assert("foo" /* ERROR boolean constant */ )
+	assert(x /* ERROR boolean constant */)
+	assert(true)
+	assert /* ERROR failed */ (false)
+	_ = assert(true)
+
+	var s []byte
+	assert(s... /* ERROR invalid use of \.\.\. */ )
+}
+
+func assert2() {
+	f1 := func() (x bool) { return }
+	f2 := func() (x bool) { return }
+	assert(f0 /* ERROR used as value */ ())
+	assert(f1 /* ERROR boolean constant */ ())
+	assert(f2 /* ERROR boolean constant */ ())
+}
+
+// self-testing only
+func trace1() {
+	// Uncomment the code below to test trace - will produce console output
+	// _ = trace /* ERROR no value */ ()
+	// _ = trace(1)
+	// _ = trace(true, 1.2, '\'', "foo", 42i, "foo" <= "bar")
+
+	var s []byte
+	trace(s... /* ERROR invalid use of \.\.\. */ )
+}
+
+func trace2() {
+	f1 := func() (x int) { return }
+	f2 := func() (x int, y string) { return }
+	f3 := func() (x int, y string, z []int) { return }
+	_ = f1
+	_ = f2
+	_ = f3
+	// Uncomment the code below to test trace - will produce console output
+	// trace(f0())
+	// trace(f1())
+	// trace(f2())
+	// trace(f3())
+	// trace(f0(), 1)
+	// trace(f1(), 1, 2)
+	// trace(f2(), 1, 2, 3)
+	// trace(f3(), 1, 2, 3, 4)
+}
diff --git a/src/internal/types/testdata/check/builtins1.go b/src/internal/types/testdata/check/builtins1.go
new file mode 100644
index 0000000..3348861
--- /dev/null
+++ b/src/internal/types/testdata/check/builtins1.go
@@ -0,0 +1,288 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file tests built-in calls on generic types.
+
+package builtins
+
+import "unsafe"
+
+// clear
+
+func _[T any](x T) {
+	clear(x /* ERROR cannot clear x */)
+}
+
+func _[T ~map[int]string | ~[]byte | ~*[10]int](x T) {
+	clear(x)
+}
+
+func _[T ~map[int]string | ~[]byte | ~*[10]int | string](x T) {
+	clear(x /* ERROR cannot clear x */)
+}
+
+// close
+
+type C0 interface{ int }
+type C1 interface{ chan int }
+type C2 interface{ chan int | <-chan int }
+type C3 interface{ chan int | chan float32 }
+type C4 interface{ chan int | chan<- int }
+type C5[T any] interface{ ~chan T | chan<- T }
+
+func _[T any](ch T) {
+	close(ch /* ERROR cannot close non-channel */)
+}
+
+func _[T C0](ch T) {
+	close(ch /* ERROR cannot close non-channel */)
+}
+
+func _[T C1](ch T) {
+	close(ch)
+}
+
+func _[T C2](ch T) {
+	close(ch /* ERROR cannot close receive-only channel */)
+}
+
+func _[T C3](ch T) {
+	close(ch)
+}
+
+func _[T C4](ch T) {
+	close(ch)
+}
+
+func _[T C5[X], X any](ch T) {
+	close(ch)
+}
+
+// copy
+
+func _[T any](x, y T) {
+	copy(x /* ERROR copy expects slice arguments */ , y)
+}
+
+func _[T ~[]byte](x, y T) {
+	copy(x, y)
+	copy(x, "foo")
+	copy("foo" /* ERROR expects slice arguments */ , y)
+
+	var x2 []byte
+	copy(x2, y) // element types are identical
+	copy(y, x2) // element types are identical
+
+	type myByte byte
+	var x3 []myByte
+	copy(x3 /* ERROR different element types */ , y)
+	copy(y /* ERROR different element types */ , x3)
+}
+
+func _[T ~[]E, E any](x T, y []E) {
+	copy(x, y)
+	copy(x /* ERROR different element types */ , "foo")
+}
+
+func _[T ~string](x []byte, y T) {
+	copy(x, y)
+	copy(y /* ERROR expects slice arguments */ , x)
+}
+
+func _[T ~[]byte|~string](x T, y []byte) {
+	copy(x /* ERROR expects slice arguments */ , y)
+	copy(y, x)
+}
+
+type L0 []int
+type L1 []int
+
+func _[T L0 | L1](x, y T) {
+	copy(x, y)
+}
+
+// delete
+
+type M0 interface{ int }
+type M1 interface{ map[string]int }
+type M2 interface { map[string]int | map[string]float64 }
+type M3 interface{ map[string]int | map[rune]int }
+type M4[K comparable, V any] interface{ map[K]V | map[rune]V }
+
+func _[T any](m T) {
+	delete(m /* ERROR not a map */, "foo")
+}
+
+func _[T M0](m T) {
+	delete(m /* ERROR not a map */, "foo")
+}
+
+func _[T M1](m T) {
+	delete(m, "foo")
+}
+
+func _[T M2](m T) {
+	delete(m, "foo")
+	delete(m, 0 /* ERROR cannot use .* as string */)
+}
+
+func _[T M3](m T) {
+	delete(m /* ERROR must have identical key types */, "foo")
+}
+
+func _[T M4[rune, V], V any](m T) {
+	delete(m, 'k')
+}
+
+func _[T M4[K, V], K comparable, V any](m T) {
+	delete(m /* ERROR must have identical key types */, "foo")
+}
+
+// make
+
+type myChan chan int
+
+func _[
+	S1 ~[]int,
+	S2 ~[]int | ~chan int,
+
+	M1 ~map[string]int,
+	M2 ~map[string]int | ~chan int,
+
+	C1 ~chan int,
+	C2 ~chan int | ~chan string,
+	C3 chan int | myChan, // single underlying type
+]() {
+	type S0 []int
+	_ = make([]int, 10)
+	_ = make(S0, 10)
+	_ = make(S1, 10)
+	_ = make() /* ERROR not enough arguments */
+	_ = make /* ERROR expects 2 or 3 arguments */ (S1)
+	_ = make(S1, 10, 20)
+	_ = make /* ERROR expects 2 or 3 arguments */ (S1, 10, 20, 30)
+	_ = make(S2 /* ERROR cannot make S2: no core type */ , 10)
+
+	type M0 map[string]int
+	_ = make(map[string]int)
+	_ = make(M0)
+	_ = make(M1)
+	_ = make(M1, 10)
+	_ = make/* ERROR expects 1 or 2 arguments */(M1, 10, 20)
+	_ = make(M2 /* ERROR cannot make M2: no core type */ )
+
+	type C0 chan int
+	_ = make(chan int)
+	_ = make(C0)
+	_ = make(C1)
+	_ = make(C1, 10)
+	_ = make/* ERROR expects 1 or 2 arguments */(C1, 10, 20)
+	_ = make(C2 /* ERROR cannot make C2: no core type */ )
+	_ = make(C3)
+}
+
+// unsafe.Alignof
+
+func _[T comparable]() {
+	var (
+		b int64
+		a [10]T
+		s struct{ f T }
+		p *T
+		l []T
+		f func(T)
+		i interface{ m() T }
+		c chan T
+		m map[T]T
+		t T
+	)
+
+	const bb = unsafe.Alignof(b)
+	assert(bb == 8)
+	const _ = unsafe /* ERROR not constant */ .Alignof(a)
+	const _ = unsafe /* ERROR not constant */ .Alignof(s)
+	const pp = unsafe.Alignof(p)
+	assert(pp == 8)
+	const ll = unsafe.Alignof(l)
+	assert(ll == 8)
+	const ff = unsafe.Alignof(f)
+	assert(ff == 8)
+	const ii = unsafe.Alignof(i)
+	assert(ii == 8)
+	const cc = unsafe.Alignof(c)
+	assert(cc == 8)
+	const mm = unsafe.Alignof(m)
+	assert(mm == 8)
+	const _ = unsafe /* ERROR not constant */ .Alignof(t)
+}
+
+// unsafe.Offsetof
+
+func _[T comparable]() {
+	var (
+		b struct{ _, f int64 }
+		a struct{ _, f [10]T }
+		s struct{ _, f struct{ f T } }
+		p struct{ _, f *T }
+		l struct{ _, f []T }
+		f struct{ _, f func(T) }
+		i struct{ _, f interface{ m() T } }
+		c struct{ _, f chan T }
+		m struct{ _, f map[T]T }
+		t struct{ _, f T }
+	)
+
+	const bb = unsafe.Offsetof(b.f)
+	assert(bb == 8)
+	const _ = unsafe /* ERROR not constant */ .Alignof(a)
+	const _ = unsafe /* ERROR not constant */ .Alignof(s)
+	const pp = unsafe.Offsetof(p.f)
+	assert(pp == 8)
+	const ll = unsafe.Offsetof(l.f)
+	assert(ll == 24)
+	const ff = unsafe.Offsetof(f.f)
+	assert(ff == 8)
+	const ii = unsafe.Offsetof(i.f)
+	assert(ii == 16)
+	const cc = unsafe.Offsetof(c.f)
+	assert(cc == 8)
+	const mm = unsafe.Offsetof(m.f)
+	assert(mm == 8)
+	const _ = unsafe /* ERROR not constant */ .Alignof(t)
+}
+
+// unsafe.Sizeof
+
+func _[T comparable]() {
+	var (
+		b int64
+		a [10]T
+		s struct{ f T }
+		p *T
+		l []T
+		f func(T)
+		i interface{ m() T }
+		c chan T
+		m map[T]T
+		t T
+	)
+
+	const bb = unsafe.Sizeof(b)
+	assert(bb == 8)
+	const _ = unsafe /* ERROR not constant */ .Alignof(a)
+	const _ = unsafe /* ERROR not constant */ .Alignof(s)
+	const pp = unsafe.Sizeof(p)
+	assert(pp == 8)
+	const ll = unsafe.Sizeof(l)
+	assert(ll == 24)
+	const ff = unsafe.Sizeof(f)
+	assert(ff == 8)
+	const ii = unsafe.Sizeof(i)
+	assert(ii == 16)
+	const cc = unsafe.Sizeof(c)
+	assert(cc == 8)
+	const mm = unsafe.Sizeof(m)
+	assert(mm == 8)
+	const _ = unsafe /* ERROR not constant */ .Alignof(t)
+}
diff --git a/src/internal/types/testdata/check/chans.go b/src/internal/types/testdata/check/chans.go
new file mode 100644
index 0000000..fad2bce
--- /dev/null
+++ b/src/internal/types/testdata/check/chans.go
@@ -0,0 +1,62 @@
+package chans
+
+import "runtime"
+
+// Ranger returns a Sender and a Receiver. The Receiver provides a
+// Next method to retrieve values. The Sender provides a Send method
+// to send values and a Close method to stop sending values. The Next
+// method indicates when the Sender has been closed, and the Send
+// method indicates when the Receiver has been freed.
+//
+// This is a convenient way to exit a goroutine sending values when
+// the receiver stops reading them.
+func Ranger[T any]() (*Sender[T], *Receiver[T]) {
+	c := make(chan T)
+	d := make(chan bool)
+	s := &Sender[T]{values: c, done: d}
+	r := &Receiver[T]{values: c, done: d}
+	runtime.SetFinalizer(r, r.finalize)
+	return s, r
+}
+
+// A sender is used to send values to a Receiver.
+type Sender[T any] struct {
+	values chan<- T
+	done <-chan bool
+}
+
+// Send sends a value to the receiver. It returns whether any more
+// values may be sent; if it returns false the value was not sent.
+func (s *Sender[T]) Send(v T) bool {
+	select {
+	case s.values <- v:
+		return true
+	case <-s.done:
+		return false
+	}
+}
+
+// Close tells the receiver that no more values will arrive.
+// After Close is called, the Sender may no longer be used.
+func (s *Sender[T]) Close() {
+	close(s.values)
+}
+
+// A Receiver receives values from a Sender.
+type Receiver[T any] struct {
+	values <-chan T
+	done chan<- bool
+}
+
+// Next returns the next value from the channel. The bool result
+// indicates whether the value is valid, or whether the Sender has
+// been closed and no more values will be received.
+func (r *Receiver[T]) Next() (T, bool) {
+	v, ok := <-r.values
+	return v, ok
+}
+
+// finalize is a finalizer for the receiver.
+func (r *Receiver[T]) finalize() {
+	close(r.done)
+}
diff --git a/src/internal/types/testdata/check/compliterals.go b/src/internal/types/testdata/check/compliterals.go
new file mode 100644
index 0000000..60eac97
--- /dev/null
+++ b/src/internal/types/testdata/check/compliterals.go
@@ -0,0 +1,22 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Composite literals with parameterized types
+
+package comp_literals
+
+type myStruct struct {
+	f int
+}
+
+type slice[E any] []E
+
+func struct_literals[S struct{f int}|myStruct]() {
+	_ = S{}
+	_ = S{0}
+	_ = S{f: 0}
+
+        _ = slice[int]{1, 2, 3}
+        _ = slice[S]{{}, {0}, {f:0}}
+}
diff --git a/src/internal/types/testdata/check/const0.go b/src/internal/types/testdata/check/const0.go
new file mode 100644
index 0000000..402e6cf
--- /dev/null
+++ b/src/internal/types/testdata/check/const0.go
@@ -0,0 +1,382 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// constant declarations
+
+package const0
+
+import "unsafe"
+
+// constants declarations must be initialized by constants
+var x = 0
+const c0 = x /* ERROR "not constant" */
+
+// typed constants must have constant types
+const _ interface /* ERROR invalid constant type */ {} = 0
+
+func _ () {
+	const _ interface /* ERROR invalid constant type */ {} = 0
+	for i := 0; i < 10; i++ {} // don't crash with non-nil iota here
+}
+
+// untyped constants
+const (
+	// boolean values
+	ub0 = false
+	ub1 = true
+	ub2 = 2 < 1
+	ub3 = ui1 == uf1
+	ub4 = true == 0 /* ERROR "mismatched types untyped bool and untyped int" */
+
+	// integer values
+	ui0 = 0
+	ui1 = 1
+	ui2 = 42
+	ui3 = 3141592653589793238462643383279502884197169399375105820974944592307816406286
+	ui4 = -10
+
+	ui5 = ui0 + ui1
+	ui6 = ui1 - ui1
+	ui7 = ui2 * ui1
+	ui8 = ui3 / ui3
+	ui9 = ui3 % ui3
+
+	ui10 = 1 / 0 /* ERROR "division by zero" */
+	ui11 = ui1 / 0 /* ERROR "division by zero" */
+	ui12 = ui3 / ui0 /* ERROR "division by zero" */
+	ui13 = 1 % 0 /* ERROR "division by zero" */
+	ui14 = ui1 % 0 /* ERROR "division by zero" */
+	ui15 = ui3 % ui0 /* ERROR "division by zero" */
+
+	ui16 = ui2 & ui3
+	ui17 = ui2 | ui3
+	ui18 = ui2 ^ ui3
+	ui19 = 1 /* ERROR "invalid operation" */ % 1.0
+
+	// floating point values
+	uf0 = 0.
+	uf1 = 1.
+	uf2 = 4.2e1
+	uf3 = 3.141592653589793238462643383279502884197169399375105820974944592307816406286
+	uf4 = 1e-1
+
+	uf5 = uf0 + uf1
+	uf6 = uf1 - uf1
+	uf7 = uf2 * uf1
+	uf8 = uf3 / uf3
+	uf9 = uf3 /* ERROR "not defined" */ % uf3
+
+	uf10 = 1 / 0 /* ERROR "division by zero" */
+	uf11 = uf1 / 0 /* ERROR "division by zero" */
+	uf12 = uf3 / uf0 /* ERROR "division by zero" */
+
+	uf16 = uf2 /* ERROR "not defined" */ & uf3
+	uf17 = uf2 /* ERROR "not defined" */ | uf3
+	uf18 = uf2 /* ERROR "not defined" */ ^ uf3
+
+	// complex values
+	uc0 = 0.i
+	uc1 = 1.i
+	uc2 = 4.2e1i
+	uc3 = 3.141592653589793238462643383279502884197169399375105820974944592307816406286i
+	uc4 = 1e-1i
+
+	uc5 = uc0 + uc1
+	uc6 = uc1 - uc1
+	uc7 = uc2 * uc1
+	uc8 = uc3 / uc3
+	uc9 = uc3 /* ERROR "not defined" */ % uc3
+
+	uc10 = 1 / 0 /* ERROR "division by zero" */
+	uc11 = uc1 / 0 /* ERROR "division by zero" */
+	uc12 = uc3 / uc0 /* ERROR "division by zero" */
+
+	uc16 = uc2 /* ERROR "not defined" */ & uc3
+	uc17 = uc2 /* ERROR "not defined" */ | uc3
+	uc18 = uc2 /* ERROR "not defined" */ ^ uc3
+)
+
+type (
+	mybool bool
+	myint int
+	myfloat float64
+	mycomplex complex128
+)
+
+// typed constants
+const (
+	// boolean values
+	tb0 bool = false
+	tb1 bool = true
+	tb2 mybool = 2 < 1
+	tb3 mybool = ti1 == tf1 /* ERROR "mismatched types" */
+
+	// integer values
+	ti0 int8 = ui0
+	ti1 int32 = ui1
+	ti2 int64 = ui2
+	ti3 myint = ui3 /* ERROR "overflows" */
+	ti4 myint = ui4
+
+	ti5 = ti0 /* ERROR "mismatched types" */ + ti1
+	ti6 = ti1 - ti1
+	ti7 = ti2 /* ERROR "mismatched types" */ * ti1
+	ti8 = ti3 / ti3
+	ti9 = ti3 % ti3
+
+	ti10 = 1 / 0 /* ERROR "division by zero" */
+	ti11 = ti1 / 0 /* ERROR "division by zero" */
+	ti12 = ti3 /* ERROR "mismatched types" */ / ti0
+	ti13 = 1 % 0 /* ERROR "division by zero" */
+	ti14 = ti1 % 0 /* ERROR "division by zero" */
+	ti15 = ti3 /* ERROR "mismatched types" */ % ti0
+
+	ti16 = ti2 /* ERROR "mismatched types" */ & ti3
+	ti17 = ti2 /* ERROR "mismatched types" */ | ti4
+	ti18 = ti2 ^ ti5 // no mismatched types error because the type of ti5 is unknown
+
+	// floating point values
+	tf0 float32 = 0.
+	tf1 float32 = 1.
+	tf2 float64 = 4.2e1
+	tf3 myfloat = 3.141592653589793238462643383279502884197169399375105820974944592307816406286
+	tf4 myfloat = 1e-1
+
+	tf5 = tf0 + tf1
+	tf6 = tf1 - tf1
+	tf7 = tf2 /* ERROR "mismatched types" */ * tf1
+	tf8 = tf3 / tf3
+	tf9 = tf3 /* ERROR "not defined" */ % tf3
+
+	tf10 = 1 / 0 /* ERROR "division by zero" */
+	tf11 = tf1 / 0 /* ERROR "division by zero" */
+	tf12 = tf3 /* ERROR "mismatched types" */ / tf0
+
+	tf16 = tf2 /* ERROR "mismatched types" */ & tf3
+	tf17 = tf2 /* ERROR "mismatched types" */ | tf3
+	tf18 = tf2 /* ERROR "mismatched types" */ ^ tf3
+
+	// complex values
+	tc0 = 0.i
+	tc1 = 1.i
+	tc2 = 4.2e1i
+	tc3 = 3.141592653589793238462643383279502884197169399375105820974944592307816406286i
+	tc4 = 1e-1i
+
+	tc5 = tc0 + tc1
+	tc6 = tc1 - tc1
+	tc7 = tc2 * tc1
+	tc8 = tc3 / tc3
+	tc9 = tc3 /* ERROR "not defined" */ % tc3
+
+	tc10 = 1 / 0 /* ERROR "division by zero" */
+	tc11 = tc1 / 0 /* ERROR "division by zero" */
+	tc12 = tc3 / tc0 /* ERROR "division by zero" */
+
+	tc16 = tc2 /* ERROR "not defined" */ & tc3
+	tc17 = tc2 /* ERROR "not defined" */ | tc3
+	tc18 = tc2 /* ERROR "not defined" */ ^ tc3
+)
+
+// initialization cycles
+const (
+	a /* ERROR "initialization cycle" */ = a
+	b /* ERROR "initialization cycle" */ , c /* ERROR "initialization cycle" */, d, e = e, d, c, b // TODO(gri) should only have one cycle error
+	f float64 = d
+)
+
+// multiple initialization
+const (
+	a1, a2, a3 = 7, 3.1415926, "foo"
+	b1, b2, b3 = b3, b1, 42
+	c1, c2, c3  /* ERROR "missing init expr for c3" */ = 1, 2
+	d1, d2, d3 = 1, 2, 3, 4 /* ERROR "extra init expr 4" */
+	_p0 = assert(a1 == 7)
+	_p1 = assert(a2 == 3.1415926)
+	_p2 = assert(a3 == "foo")
+	_p3 = assert(b1 == 42)
+	_p4 = assert(b2 == 42)
+	_p5 = assert(b3 == 42)
+)
+
+func _() {
+	const (
+		a1, a2, a3 = 7, 3.1415926, "foo"
+		b1, b2, b3 = b3, b1, 42
+		c1, c2, c3  /* ERROR "missing init expr for c3" */ = 1, 2
+		d1, d2, d3 = 1, 2, 3, 4 /* ERROR "extra init expr 4" */
+		_p0 = assert(a1 == 7)
+		_p1 = assert(a2 == 3.1415926)
+		_p2 = assert(a3 == "foo")
+		_p3 = assert(b1 == 42)
+		_p4 = assert(b2 == 42)
+		_p5 = assert(b3 == 42)
+	)
+}
+
+// iota
+const (
+	iota0 = iota
+	iota1 = iota
+	iota2 = iota*2
+	_a0 = assert(iota0 == 0)
+	_a1 = assert(iota1 == 1)
+	_a2 = assert(iota2 == 4)
+	iota6 = iota*3
+
+	iota7
+	iota8
+	_a3 = assert(iota7 == 21)
+	_a4 = assert(iota8 == 24)
+)
+
+const (
+	_b0 = iota
+	_b1 = assert(iota + iota2 == 5)
+	_b2 = len([iota]int{}) // iota may appear in a type!
+	_b3 = assert(_b2 == 2)
+	_b4 = len(A{})
+)
+
+type A [iota /* ERROR "cannot use iota" */ ]int
+
+// constant expressions with operands across different
+// constant declarations must use the right iota values
+const (
+	_c0 = iota
+	_c1
+	_c2
+	_x = _c2 + _d1 + _e0 // 3
+)
+
+const (
+	_d0 = iota
+	_d1
+)
+
+const (
+	_e0 = iota
+)
+
+var _ = assert(_x == 3)
+
+// special cases
+const (
+	_n0 = nil /* ERROR "not constant" */
+	_n1 = [ /* ERROR "not constant" */ ]int{}
+)
+
+// iotas must not be usable in expressions outside constant declarations
+type _ [iota /* ERROR "iota outside constant decl" */ ]byte
+var _ = iota /* ERROR "iota outside constant decl" */
+func _() {
+	_ = iota /* ERROR "iota outside constant decl" */
+	const _ = iota
+	_ = iota /* ERROR "iota outside constant decl" */
+}
+
+func _() {
+	iota := 123
+	const x = iota /* ERROR "is not constant" */
+	var y = iota
+	_ = y
+}
+
+// iotas are usable inside closures in constant declarations (#22345)
+const (
+	_ = iota
+	_ = len([iota]byte{})
+	_ = unsafe.Sizeof(iota)
+	_ = unsafe.Sizeof(func() { _ = iota })
+	_ = unsafe.Sizeof(func() { var _ = iota })
+	_ = unsafe.Sizeof(func() { const _ = iota })
+	_ = unsafe.Sizeof(func() { type _ [iota]byte })
+	_ = unsafe.Sizeof(func() { func() int { return iota }() })
+)
+
+// verify inner and outer const declarations have distinct iotas
+const (
+	zero = iota
+	one  = iota
+	_    = unsafe.Sizeof(func() {
+		var x [iota]int // [2]int
+		const (
+			Zero = iota
+			One
+			Two
+			_ = unsafe.Sizeof([iota-1]int{} == x) // assert types are equal
+			_ = unsafe.Sizeof([Two]int{} == x)    // assert types are equal
+		)
+		var z [iota]int                           // [2]int
+		_ = unsafe.Sizeof([2]int{} == z)          // assert types are equal
+	})
+	three = iota // the sequence continues
+)
+var _ [three]int = [3]int{} // assert 'three' has correct value
+
+var (
+	_ = iota /* ERROR "iota outside constant decl" */
+	_ = unsafe.Sizeof(iota  /* ERROR "iota outside constant decl" */ )
+	_ = unsafe.Sizeof(func() { _ = iota /* ERROR "iota outside constant decl" */ })
+	_ = unsafe.Sizeof(func() { var _ = iota /* ERROR "iota outside constant decl" */ })
+	_ = unsafe.Sizeof(func() { type _ [iota /* ERROR "iota outside constant decl" */ ]byte })
+	_ = unsafe.Sizeof(func() { func() int { return iota /* ERROR "iota outside constant decl" */ }() })
+)
+
+// constant arithmetic precision and rounding must lead to expected (integer) results
+var _ = []int64{
+	0.0005 * 1e9,
+	0.001 * 1e9,
+	0.005 * 1e9,
+	0.01 * 1e9,
+	0.05 * 1e9,
+	0.1 * 1e9,
+	0.5 * 1e9,
+	1 * 1e9,
+	5 * 1e9,
+}
+
+const _ = unsafe.Sizeof(func() {
+	const _ = 0
+	_ = iota
+
+	const (
+	   zero = iota
+	   one
+	)
+	assert(one == 1)
+	assert(iota == 0)
+})
+
+// issue #52438
+const i1 = iota
+const i2 = iota
+const i3 = iota
+
+func _() {
+	assert(i1 == 0)
+	assert(i2 == 0)
+	assert(i3 == 0)
+
+	const i4 = iota
+	const i5 = iota
+	const i6 = iota
+
+	assert(i4 == 0)
+	assert(i5 == 0)
+	assert(i6 == 0)
+}
+
+// untyped constants must not get arbitrarily large
+const prec = 512 // internal maximum precision for integers
+const maxInt = (1<<(prec/2) - 1) * (1<<(prec/2) + 1) // == 1<<prec - 1
+
+const _ = maxInt + /* ERROR constant addition overflow */ 1
+const _ = -maxInt - /* ERROR constant subtraction overflow */ 1
+const _ = maxInt ^ /* ERROR constant bitwise XOR overflow */ -1
+const _ = maxInt * /* ERROR constant multiplication overflow */ 2
+const _ = maxInt << /* ERROR constant shift overflow */ 2
+const _ = 1 << /* ERROR constant shift overflow */ prec
+
+const _ = ^ /* ERROR constant bitwise complement overflow */ maxInt
diff --git a/src/internal/types/testdata/check/const1.go b/src/internal/types/testdata/check/const1.go
new file mode 100644
index 0000000..c912801
--- /dev/null
+++ b/src/internal/types/testdata/check/const1.go
@@ -0,0 +1,334 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// constant conversions
+
+package const1
+
+import "math"
+
+const(
+	mi = ^int(0)
+	mu = ^uint(0)
+	mp = ^uintptr(0)
+
+	logSizeofInt     = uint(mi>>8&1 + mi>>16&1 + mi>>32&1)
+	logSizeofUint    = uint(mu>>8&1 + mu>>16&1 + mu>>32&1)
+	logSizeofUintptr = uint(mp>>8&1 + mp>>16&1 + mp>>32&1)
+)
+
+const (
+	minInt8 = -1<<(8<<iota - 1)
+	minInt16
+	minInt32
+	minInt64
+	minInt = -1<<(8<<logSizeofInt - 1)
+)
+
+const (
+	maxInt8 = 1<<(8<<iota - 1) - 1
+	maxInt16
+	maxInt32
+	maxInt64
+	maxInt = 1<<(8<<logSizeofInt - 1) - 1
+)
+
+const (
+	maxUint8 = 1<<(8<<iota) - 1
+	maxUint16
+	maxUint32
+	maxUint64
+	maxUint    = 1<<(8<<logSizeofUint) - 1
+	maxUintptr = 1<<(8<<logSizeofUintptr) - 1
+)
+
+const (
+	smallestFloat32 = 1.0 / (1<<(127 - 1 + 23))
+	// TODO(gri) The compiler limits integers to 512 bit and thus
+	//           we cannot compute the value (1<<(1023 - 1 + 52))
+	//           without overflow. For now we match the compiler.
+	//           See also issue #44057.
+	// smallestFloat64 = 1.0 / (1<<(1023 - 1 + 52))
+	smallestFloat64 = math.SmallestNonzeroFloat64
+)
+
+const (
+	_ = assert(smallestFloat32 > 0)
+	_ = assert(smallestFloat64 > 0)
+)
+
+const (
+	maxFloat32 = 1<<127 * (1<<24 - 1) / (1.0<<23)
+	// TODO(gri) The compiler limits integers to 512 bit and thus
+	//           we cannot compute the value 1<<1023
+	//           without overflow. For now we match the compiler.
+	//           See also issue #44057.
+	// maxFloat64 = 1<<1023 * (1<<53 - 1) / (1.0<<52)
+	maxFloat64 = math.MaxFloat64
+)
+
+const (
+	_ int8 = minInt8 /* ERROR "overflows" */ - 1
+	_ int8 = minInt8
+	_ int8 = maxInt8
+	_ int8 = maxInt8 /* ERROR "overflows" */ + 1
+	_ int8 = smallestFloat64 /* ERROR "truncated" */
+
+	_ = int8(minInt8 /* ERROR "cannot convert" */ - 1)
+	_ = int8(minInt8)
+	_ = int8(maxInt8)
+	_ = int8(maxInt8 /* ERROR "cannot convert" */ + 1)
+	_ = int8(smallestFloat64 /* ERROR "cannot convert" */)
+)
+
+const (
+	_ int16 = minInt16 /* ERROR "overflows" */ - 1
+	_ int16 = minInt16
+	_ int16 = maxInt16
+	_ int16 = maxInt16 /* ERROR "overflows" */ + 1
+	_ int16 = smallestFloat64 /* ERROR "truncated" */
+
+	_ = int16(minInt16 /* ERROR "cannot convert" */ - 1)
+	_ = int16(minInt16)
+	_ = int16(maxInt16)
+	_ = int16(maxInt16 /* ERROR "cannot convert" */ + 1)
+	_ = int16(smallestFloat64 /* ERROR "cannot convert" */)
+)
+
+const (
+	_ int32 = minInt32 /* ERROR "overflows" */ - 1
+	_ int32 = minInt32
+	_ int32 = maxInt32
+	_ int32 = maxInt32 /* ERROR "overflows" */ + 1
+	_ int32 = smallestFloat64 /* ERROR "truncated" */
+
+	_ = int32(minInt32 /* ERROR "cannot convert" */ - 1)
+	_ = int32(minInt32)
+	_ = int32(maxInt32)
+	_ = int32(maxInt32 /* ERROR "cannot convert" */ + 1)
+	_ = int32(smallestFloat64 /* ERROR "cannot convert" */)
+)
+
+const (
+	_ int64 = minInt64 /* ERROR "overflows" */ - 1
+	_ int64 = minInt64
+	_ int64 = maxInt64
+	_ int64 = maxInt64 /* ERROR "overflows" */ + 1
+	_ int64 = smallestFloat64 /* ERROR "truncated" */
+
+	_ = int64(minInt64 /* ERROR "cannot convert" */ - 1)
+	_ = int64(minInt64)
+	_ = int64(maxInt64)
+	_ = int64(maxInt64 /* ERROR "cannot convert" */ + 1)
+	_ = int64(smallestFloat64 /* ERROR "cannot convert" */)
+)
+
+const (
+	_ int = minInt /* ERROR "overflows" */ - 1
+	_ int = minInt
+	_ int = maxInt
+	_ int = maxInt /* ERROR "overflows" */ + 1
+	_ int = smallestFloat64 /* ERROR "truncated" */
+
+	_ = int(minInt /* ERROR "cannot convert" */ - 1)
+	_ = int(minInt)
+	_ = int(maxInt)
+	_ = int(maxInt /* ERROR "cannot convert" */ + 1)
+	_ = int(smallestFloat64 /* ERROR "cannot convert" */)
+)
+
+const (
+	_ uint8 = 0 /* ERROR "overflows" */ - 1
+	_ uint8 = 0
+	_ uint8 = maxUint8
+	_ uint8 = maxUint8 /* ERROR "overflows" */ + 1
+	_ uint8 = smallestFloat64 /* ERROR "truncated" */
+
+	_ = uint8(0 /* ERROR "cannot convert" */ - 1)
+	_ = uint8(0)
+	_ = uint8(maxUint8)
+	_ = uint8(maxUint8 /* ERROR "cannot convert" */ + 1)
+	_ = uint8(smallestFloat64 /* ERROR "cannot convert" */)
+)
+
+const (
+	_ uint16 = 0 /* ERROR "overflows" */ - 1
+	_ uint16 = 0
+	_ uint16 = maxUint16
+	_ uint16 = maxUint16 /* ERROR "overflows" */ + 1
+	_ uint16 = smallestFloat64 /* ERROR "truncated" */
+
+	_ = uint16(0 /* ERROR "cannot convert" */ - 1)
+	_ = uint16(0)
+	_ = uint16(maxUint16)
+	_ = uint16(maxUint16 /* ERROR "cannot convert" */ + 1)
+	_ = uint16(smallestFloat64 /* ERROR "cannot convert" */)
+)
+
+const (
+	_ uint32 = 0 /* ERROR "overflows" */ - 1
+	_ uint32 = 0
+	_ uint32 = maxUint32
+	_ uint32 = maxUint32 /* ERROR "overflows" */ + 1
+	_ uint32 = smallestFloat64 /* ERROR "truncated" */
+
+	_ = uint32(0 /* ERROR "cannot convert" */ - 1)
+	_ = uint32(0)
+	_ = uint32(maxUint32)
+	_ = uint32(maxUint32 /* ERROR "cannot convert" */ + 1)
+	_ = uint32(smallestFloat64 /* ERROR "cannot convert" */)
+)
+
+const (
+	_ uint64 = 0 /* ERROR "overflows" */ - 1
+	_ uint64 = 0
+	_ uint64 = maxUint64
+	_ uint64 = maxUint64 /* ERROR "overflows" */ + 1
+	_ uint64 = smallestFloat64 /* ERROR "truncated" */
+
+	_ = uint64(0 /* ERROR "cannot convert" */ - 1)
+	_ = uint64(0)
+	_ = uint64(maxUint64)
+	_ = uint64(maxUint64 /* ERROR "cannot convert" */ + 1)
+	_ = uint64(smallestFloat64 /* ERROR "cannot convert" */)
+)
+
+const (
+	_ uint = 0 /* ERROR "overflows" */ - 1
+	_ uint = 0
+	_ uint = maxUint
+	_ uint = maxUint /* ERROR "overflows" */ + 1
+	_ uint = smallestFloat64 /* ERROR "truncated" */
+
+	_ = uint(0 /* ERROR "cannot convert" */ - 1)
+	_ = uint(0)
+	_ = uint(maxUint)
+	_ = uint(maxUint /* ERROR "cannot convert" */ + 1)
+	_ = uint(smallestFloat64 /* ERROR "cannot convert" */)
+)
+
+const (
+	_ uintptr = 0 /* ERROR "overflows" */ - 1
+	_ uintptr = 0
+	_ uintptr = maxUintptr
+	_ uintptr = maxUintptr /* ERROR "overflows" */ + 1
+	_ uintptr = smallestFloat64 /* ERROR "truncated" */
+
+	_ = uintptr(0 /* ERROR "cannot convert" */ - 1)
+	_ = uintptr(0)
+	_ = uintptr(maxUintptr)
+	_ = uintptr(maxUintptr /* ERROR "cannot convert" */ + 1)
+	_ = uintptr(smallestFloat64 /* ERROR "cannot convert" */)
+)
+
+const (
+	_ float32 = minInt64
+	_ float64 = minInt64
+	_ complex64 = minInt64
+	_ complex128 = minInt64
+
+	_ = float32(minInt64)
+	_ = float64(minInt64)
+	_ = complex64(minInt64)
+	_ = complex128(minInt64)
+)
+
+const (
+	_ float32 = maxUint64
+	_ float64 = maxUint64
+	_ complex64 = maxUint64
+	_ complex128 = maxUint64
+
+	_ = float32(maxUint64)
+	_ = float64(maxUint64)
+	_ = complex64(maxUint64)
+	_ = complex128(maxUint64)
+)
+
+// TODO(gri) find smaller deltas below
+
+const delta32 = maxFloat32/(1 << 23)
+
+const (
+	_ float32 = - /* ERROR "overflow" */ (maxFloat32 + delta32)
+	_ float32 = -maxFloat32
+	_ float32 = maxFloat32
+	_ float32 = maxFloat32 /* ERROR "overflow" */ + delta32
+
+	_ = float32(- /* ERROR "cannot convert" */ (maxFloat32 + delta32))
+	_ = float32(-maxFloat32)
+	_ = float32(maxFloat32)
+	_ = float32(maxFloat32 /* ERROR "cannot convert" */ + delta32)
+
+	_ = assert(float32(smallestFloat32) == smallestFloat32)
+	_ = assert(float32(smallestFloat32/2) == 0)
+	_ = assert(float32(smallestFloat64) == 0)
+	_ = assert(float32(smallestFloat64/2) == 0)
+)
+
+const delta64 = maxFloat64/(1 << 52)
+
+const (
+	_ float64 = - /* ERROR "overflow" */ (maxFloat64 + delta64)
+	_ float64 = -maxFloat64
+	_ float64 = maxFloat64
+	_ float64 = maxFloat64 /* ERROR "overflow" */ + delta64
+
+	_ = float64(- /* ERROR "cannot convert" */ (maxFloat64 + delta64))
+	_ = float64(-maxFloat64)
+	_ = float64(maxFloat64)
+	_ = float64(maxFloat64 /* ERROR "cannot convert" */ + delta64)
+
+	_ = assert(float64(smallestFloat32) == smallestFloat32)
+	_ = assert(float64(smallestFloat32/2) == smallestFloat32/2)
+	_ = assert(float64(smallestFloat64) == smallestFloat64)
+	_ = assert(float64(smallestFloat64/2) == 0)
+)
+
+const (
+	_ complex64 = - /* ERROR "overflow" */ (maxFloat32 + delta32)
+	_ complex64 = -maxFloat32
+	_ complex64 = maxFloat32
+	_ complex64 = maxFloat32 /* ERROR "overflow" */ + delta32
+
+	_ = complex64(- /* ERROR "cannot convert" */ (maxFloat32 + delta32))
+	_ = complex64(-maxFloat32)
+	_ = complex64(maxFloat32)
+	_ = complex64(maxFloat32 /* ERROR "cannot convert" */ + delta32)
+)
+
+const (
+	_ complex128 = - /* ERROR "overflow" */ (maxFloat64 + delta64)
+	_ complex128 = -maxFloat64
+	_ complex128 = maxFloat64
+	_ complex128 = maxFloat64 /* ERROR "overflow" */ + delta64
+
+	_ = complex128(- /* ERROR "cannot convert" */ (maxFloat64 + delta64))
+	_ = complex128(-maxFloat64)
+	_ = complex128(maxFloat64)
+	_ = complex128(maxFloat64 /* ERROR "cannot convert" */ + delta64)
+)
+
+// Initialization of typed constant and conversion are the same:
+const (
+	f32 = 1 + smallestFloat32
+	x32 float32 = f32
+	y32 = float32(f32)
+	_ = assert(x32 - y32 == 0)
+)
+
+const (
+	f64 = 1 + smallestFloat64
+	x64 float64 = f64
+	y64 = float64(f64)
+	_ = assert(x64 - y64 == 0)
+)
+
+const (
+	_ = int8(-1) << 7
+	_ = int8 /* ERROR "overflows" */ (-1) << 8
+
+	_ = uint32(1) << 31
+	_ = uint32 /* ERROR "overflows" */ (1) << 32
+)
diff --git a/src/internal/types/testdata/check/constdecl.go b/src/internal/types/testdata/check/constdecl.go
new file mode 100644
index 0000000..faa9b9d
--- /dev/null
+++ b/src/internal/types/testdata/check/constdecl.go
@@ -0,0 +1,160 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package constdecl
+
+import "math"
+import "unsafe"
+
+var v int
+
+// Const decls must be initialized by constants.
+const _ = v /* ERROR "not constant" */
+const _ = math /* ERROR "not constant" */ .Sin(0)
+const _ = int /* ERROR "not an expression" */
+
+func _() {
+	const _ = v /* ERROR "not constant" */
+	const _ = math /* ERROR "not constant" */ .Sin(0)
+	const _ = int /* ERROR "not an expression" */
+}
+
+// Identifier and expression arity must match.
+const _ /* ERROR "missing init expr for _" */
+const _ = 1, 2 /* ERROR "extra init expr 2" */
+
+const _ /* ERROR "missing init expr for _" */ int
+const _ int = 1, 2 /* ERROR "extra init expr 2" */
+
+const (
+	_ /* ERROR "missing init expr for _" */
+	_ = 1, 2 /* ERROR "extra init expr 2" */
+
+	_ /* ERROR "missing init expr for _" */ int
+	_ int = 1, 2 /* ERROR "extra init expr 2" */
+)
+
+const (
+	_ = 1
+	_
+	_, _ /* ERROR "missing init expr for _" */
+	_
+)
+
+const (
+	_, _ = 1, 2
+	_, _
+	_ /* ERROR "extra init expr at" */
+	_, _
+	_, _, _ /* ERROR "missing init expr for _" */
+	_, _
+)
+
+func _() {
+	const _ /* ERROR "missing init expr for _" */
+	const _ = 1, 2 /* ERROR "extra init expr 2" */
+
+	const _ /* ERROR "missing init expr for _" */ int
+	const _ int = 1, 2 /* ERROR "extra init expr 2" */
+
+	const (
+		_ /* ERROR "missing init expr for _" */
+		_ = 1, 2 /* ERROR "extra init expr 2" */
+
+		_ /* ERROR "missing init expr for _" */ int
+		_ int = 1, 2 /* ERROR "extra init expr 2" */
+	)
+
+	const (
+		_ = 1
+		_
+		_, _ /* ERROR "missing init expr for _" */
+		_
+	)
+
+	const (
+		_, _ = 1, 2
+		_, _
+		_ /* ERROR "extra init expr at" */
+		_, _
+		_, _, _ /* ERROR "missing init expr for _" */
+		_, _
+	)
+}
+
+// Test case for constant with invalid initialization.
+// Caused panic because the constant value was not set up (gri - 7/8/2014).
+func _() {
+	const (
+	    x string = missing /* ERROR "undefined" */
+	    y = x + ""
+	)
+}
+
+// Test case for constants depending on function literals (see also #22992).
+const A /* ERROR initialization cycle */ = unsafe.Sizeof(func() { _ = A })
+
+func _() {
+	// The function literal below must not see a.
+	const a = unsafe.Sizeof(func() { _ = a /* ERROR "undefined" */ })
+	const b = unsafe.Sizeof(func() { _ = a })
+
+	// The function literal below must not see x, y, or z.
+	const x, y, z = 0, 1, unsafe.Sizeof(func() { _ = x /* ERROR "undefined" */ + y /* ERROR "undefined" */ + z /* ERROR "undefined" */ })
+}
+
+// Test cases for errors in inherited constant initialization expressions.
+// Errors related to inherited initialization expressions must appear at
+// the constant identifier being declared, not at the original expression
+// (issues #42991, #42992).
+const (
+	_ byte = 255 + iota
+	/* some gap */
+	_ // ERROR overflows
+	/* some gap */
+	/* some gap */ _ /* ERROR overflows */; _ /* ERROR overflows */
+	/* some gap */
+	_ = 255 + iota
+	_ = byte /* ERROR overflows */ (255) + iota
+	_ /* ERROR overflows */
+)
+
+// Test cases from issue.
+const (
+	ok = byte(iota + 253)
+	bad
+	barn
+	bard // ERROR cannot convert
+)
+
+const (
+	c = len([1 - iota]int{})
+	d
+	e // ERROR invalid array length
+	f // ERROR invalid array length
+)
+
+// Test that identifiers in implicit (omitted) RHS
+// expressions of constant declarations are resolved
+// in the correct context; see issues #49157, #53585.
+const X = 2
+
+func _() {
+	const (
+		A    = iota // 0
+		iota = iota // 1
+		B           // 1 (iota is declared locally on prev. line)
+		C           // 1
+	)
+	assert(A == 0 && B == 1 && C == 1)
+
+	const (
+		X = X + X
+		Y
+		Z = iota
+	)
+	assert(X == 4 && Y == 8 && Z == 1)
+}
+
+// TODO(gri) move extra tests from testdata/const0.src into here
diff --git a/src/internal/types/testdata/check/conversions0.go b/src/internal/types/testdata/check/conversions0.go
new file mode 100644
index 0000000..e1336c0
--- /dev/null
+++ b/src/internal/types/testdata/check/conversions0.go
@@ -0,0 +1,93 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// conversions
+
+package conversions
+
+import "unsafe"
+
+// argument count
+var (
+	_ = int() /* ERROR "missing argument" */
+	_ = int(1, 2 /* ERROR "too many arguments" */ )
+)
+
+// numeric constant conversions are in const1.src.
+
+func string_conversions() {
+	const A = string(65)
+	assert(A == "A")
+	const E = string(-1)
+	assert(E == "\uFFFD")
+	assert(E == string(1234567890))
+
+	type myint int
+	assert(A == string(myint(65)))
+
+	type mystring string
+	const _ mystring = mystring("foo")
+
+	const _ = string(true /* ERROR "cannot convert" */ )
+	const _ = string(1.2 /* ERROR "cannot convert" */ )
+	const _ = string(nil /* ERROR "cannot convert" */ )
+
+	// issues 11357, 11353: argument must be of integer type
+	_ = string(0.0 /* ERROR "cannot convert" */ )
+	_ = string(0i /* ERROR "cannot convert" */ )
+	_ = string(1 /* ERROR "cannot convert" */ + 2i)
+}
+
+func interface_conversions() {
+	type E interface{}
+
+	type I1 interface{
+		m1()
+	}
+
+	type I2 interface{
+		m1()
+		m2(x int)
+	}
+
+	type I3 interface{
+		m1()
+		m2() int
+	}
+
+	var e E
+	var i1 I1
+	var i2 I2
+	var i3 I3
+
+	_ = E(0)
+	_ = E(nil)
+	_ = E(e)
+	_ = E(i1)
+	_ = E(i2)
+
+	_ = I1(0 /* ERROR "cannot convert" */ )
+	_ = I1(nil)
+	_ = I1(i1)
+	_ = I1(e /* ERROR "cannot convert" */ )
+	_ = I1(i2)
+
+	_ = I2(nil)
+	_ = I2(i1 /* ERROR "cannot convert" */ )
+	_ = I2(i2)
+	_ = I2(i3 /* ERROR "cannot convert" */ )
+
+	_ = I3(nil)
+	_ = I3(i1 /* ERROR "cannot convert" */ )
+	_ = I3(i2 /* ERROR "cannot convert" */ )
+	_ = I3(i3)
+
+	// TODO(gri) add more tests, improve error message
+}
+
+func issue6326() {
+	type T unsafe.Pointer
+	var x T
+	_ = uintptr(x) // see issue 6326
+}
diff --git a/src/internal/types/testdata/check/conversions1.go b/src/internal/types/testdata/check/conversions1.go
new file mode 100644
index 0000000..93a5f18
--- /dev/null
+++ b/src/internal/types/testdata/check/conversions1.go
@@ -0,0 +1,313 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test various valid and invalid struct assignments and conversions.
+// Does not compile.
+
+package conversions2
+
+type I interface {
+	m()
+}
+
+// conversions between structs
+
+func _() {
+	type S struct{}
+	type T struct{}
+	var s S
+	var t T
+	var u struct{}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u
+	s = S(s)
+	s = S(t)
+	s = S(u)
+	t = u
+	t = T(u)
+}
+
+func _() {
+	type S struct{ x int }
+	type T struct {
+		x int "foo"
+	}
+	var s S
+	var t T
+	var u struct {
+		x int "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = S(s)
+	s = S(t)
+	s = S(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = T(u)
+}
+
+func _() {
+	type E struct{ x int }
+	type S struct{ x E }
+	type T struct {
+		x E "foo"
+	}
+	var s S
+	var t T
+	var u struct {
+		x E "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = S(s)
+	s = S(t)
+	s = S(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = T(u)
+}
+
+func _() {
+	type S struct {
+		x struct {
+			x int "foo"
+		}
+	}
+	type T struct {
+		x struct {
+			x int "bar"
+		} "foo"
+	}
+	var s S
+	var t T
+	var u struct {
+		x struct {
+			x int "bar"
+		} "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = S(s)
+	s = S(t)
+	s = S(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = T(u)
+}
+
+func _() {
+	type E1 struct {
+		x int "foo"
+	}
+	type E2 struct {
+		x int "bar"
+	}
+	type S struct{ x E1 }
+	type T struct {
+		x E2 "foo"
+	}
+	var s S
+	var t T
+	var u struct {
+		x E2 "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = S(s)
+	s = S(t /* ERROR "cannot convert" */ )
+	s = S(u /* ERROR "cannot convert" */ )
+	t = u   // ERROR "cannot use .* in assignment"
+	t = T(u)
+}
+
+func _() {
+	type E struct{ x int }
+	type S struct {
+		f func(struct {
+			x int "foo"
+		})
+	}
+	type T struct {
+		f func(struct {
+			x int "bar"
+		})
+	}
+	var s S
+	var t T
+	var u struct{ f func(E) }
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = S(s)
+	s = S(t)
+	s = S(u /* ERROR "cannot convert" */ )
+	t = u   // ERROR "cannot use .* in assignment"
+	t = T(u /* ERROR "cannot convert" */ )
+}
+
+// conversions between pointers to structs
+
+func _() {
+	type S struct{}
+	type T struct{}
+	var s *S
+	var t *T
+	var u *struct{}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t)
+	s = (*S)(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = (*T)(u)
+}
+
+func _() {
+	type S struct{ x int }
+	type T struct {
+		x int "foo"
+	}
+	var s *S
+	var t *T
+	var u *struct {
+		x int "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t)
+	s = (*S)(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = (*T)(u)
+}
+
+func _() {
+	type E struct{ x int }
+	type S struct{ x E }
+	type T struct {
+		x E "foo"
+	}
+	var s *S
+	var t *T
+	var u *struct {
+		x E "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t)
+	s = (*S)(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = (*T)(u)
+}
+
+func _() {
+	type S struct {
+		x struct {
+			x int "foo"
+		}
+	}
+	type T struct {
+		x struct {
+			x int "bar"
+		} "foo"
+	}
+	var s *S
+	var t *T
+	var u *struct {
+		x struct {
+			x int "bar"
+		} "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t)
+	s = (*S)(u)
+	t = u // ERROR "cannot use .* in assignment"
+	t = (*T)(u)
+}
+
+func _() {
+	type E1 struct {
+		x int "foo"
+	}
+	type E2 struct {
+		x int "bar"
+	}
+	type S struct{ x E1 }
+	type T struct {
+		x E2 "foo"
+	}
+	var s *S
+	var t *T
+	var u *struct {
+		x E2 "bar"
+	}
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t /* ERROR "cannot convert" */ )
+	s = (*S)(u /* ERROR "cannot convert" */ )
+	t = u      // ERROR "cannot use .* in assignment"
+	t = (*T)(u)
+}
+
+func _() {
+	type E struct{ x int }
+	type S struct {
+		f func(struct {
+			x int "foo"
+		})
+	}
+	type T struct {
+		f func(struct {
+			x int "bar"
+		})
+	}
+	var s *S
+	var t *T
+	var u *struct{ f func(E) }
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t)
+	s = (*S)(u /* ERROR "cannot convert" */ )
+	t = u      // ERROR "cannot use .* in assignment"
+	t = (*T)(u /* ERROR "cannot convert" */ )
+}
+
+func _() {
+	type E struct{ x int }
+	type S struct {
+		f func(*struct {
+			x int "foo"
+		})
+	}
+	type T struct {
+		f func(*struct {
+			x int "bar"
+		})
+	}
+	var s *S
+	var t *T
+	var u *struct{ f func(E) }
+	s = s
+	s = t // ERROR "cannot use .* in assignment"
+	s = u // ERROR "cannot use .* in assignment"
+	s = (*S)(s)
+	s = (*S)(t)
+	s = (*S)(u /* ERROR "cannot convert" */ )
+	t = u      // ERROR "cannot use .* in assignment"
+	t = (*T)(u /* ERROR "cannot convert" */ )
+}
diff --git a/src/internal/types/testdata/check/cycles0.go b/src/internal/types/testdata/check/cycles0.go
new file mode 100644
index 0000000..7c00c7d
--- /dev/null
+++ b/src/internal/types/testdata/check/cycles0.go
@@ -0,0 +1,175 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cycles
+
+import "unsafe"
+
+type (
+	T0 int
+	T1 /* ERROR invalid recursive type: T1 refers to itself */ T1
+	T2 *T2
+
+	T3 /* ERROR invalid recursive type */ T4
+	T4 T5
+	T5 T3
+
+	T6 T7
+	T7 *T8
+	T8 T6
+
+	// arrays
+	A0 /* ERROR invalid recursive type */ [10]A0
+	A1 [10]*A1
+
+	A2 /* ERROR invalid recursive type */ [10]A3
+	A3 [10]A4
+	A4 A2
+
+	A5 [10]A6
+	A6 *A5
+
+	// slices
+	L0 []L0
+
+	// structs
+	S0 /* ERROR invalid recursive type: S0 refers to itself */ struct{ _ S0 }
+	S1 /* ERROR invalid recursive type: S1 refers to itself */ struct{ S1 }
+	S2 struct{ _ *S2 }
+	S3 struct{ *S3 }
+
+	S4 /* ERROR invalid recursive type */ struct{ S5 }
+	S5 struct{ S6 }
+	S6 S4
+
+	// pointers
+	P0 *P0
+	PP *struct{ PP.f /* ERROR PP.f is not a type */ }
+
+	// functions
+	F0 func(F0)
+	F1 func() F1
+	F2 func(F2) F2
+
+	// interfaces
+	I0 /* ERROR invalid recursive type: I0 refers to itself */ interface{ I0 }
+
+	I1 /* ERROR invalid recursive type */ interface{ I2 }
+	I2 interface{ I3 }
+	I3 interface{ I1 }
+
+	I4 interface{ f(I4) }
+
+	// testcase for issue 5090
+	I5 interface{ f(I6) }
+	I6 interface{ I5 }
+
+	// maps
+	M0 map[M0 /* ERROR invalid map key */ ]M0
+
+	// channels
+	C0 chan C0
+)
+
+// test case for issue #34771
+type (
+	AA /* ERROR invalid recursive type */ B
+	B C
+	C [10]D
+	D E
+	E AA
+)
+
+func _() {
+	type (
+		t1 /* ERROR invalid recursive type: t1 refers to itself */ t1
+		t2 *t2
+
+		t3 t4 /* ERROR undefined */
+		t4 t5 /* ERROR undefined */
+		t5 t3
+
+		// arrays
+		a0 /* ERROR invalid recursive type: a0 refers to itself */ [10]a0
+		a1 [10]*a1
+
+		// slices
+		l0 []l0
+
+		// structs
+		s0 /* ERROR invalid recursive type: s0 refers to itself */ struct{ _ s0 }
+		s1 /* ERROR invalid recursive type: s1 refers to itself */ struct{ s1 }
+		s2 struct{ _ *s2 }
+		s3 struct{ *s3 }
+
+		// pointers
+		p0 *p0
+
+		// functions
+		f0 func(f0)
+		f1 func() f1
+		f2 func(f2) f2
+
+		// interfaces
+		i0 /* ERROR invalid recursive type: i0 refers to itself */ interface{ i0 }
+
+		// maps
+		m0 map[m0 /* ERROR invalid map key */ ]m0
+
+		// channels
+		c0 chan c0
+	)
+}
+
+// test cases for issue 6667
+
+type A [10]map[A /* ERROR invalid map key */ ]bool
+
+type S struct {
+	m map[S /* ERROR invalid map key */ ]bool
+}
+
+// test cases for issue 7236
+// (cycle detection must not be dependent on starting point of resolution)
+
+type (
+	P1 *T9
+	T9 /* ERROR invalid recursive type: T9 refers to itself */ T9
+
+	T10 /* ERROR invalid recursive type: T10 refers to itself */ T10
+	P2 *T10
+)
+
+func (T11) m() {}
+
+type T11 /* ERROR invalid recursive type: T11 refers to itself */ struct{ T11 }
+
+type T12 /* ERROR invalid recursive type: T12 refers to itself */ struct{ T12 }
+
+func (*T12) m() {}
+
+type (
+	P3 *T13
+	T13 /* ERROR invalid recursive type */ T13
+)
+
+// test cases for issue 18643
+// (type cycle detection when non-type expressions are involved)
+type (
+	T14 [len(T14 /* ERROR invalid recursive type */ {})]int
+	T15 [][len(T15 /* ERROR invalid recursive type */ {})]int
+	T16 map[[len(T16 /* ERROR invalid recursive type */ {1:2})]int]int
+	T17 map[int][len(T17 /* ERROR invalid recursive type */ {1:2})]int
+)
+
+// Test case for types depending on function literals (see also #22992).
+type T20 chan [unsafe.Sizeof(func(ch T20){ _ = <-ch })]byte
+type T22 = chan [unsafe.Sizeof(func(ch T20){ _ = <-ch })]byte
+
+func _() {
+	type T0 func(T0)
+	type T1 /* ERROR invalid recursive type */ = func(T1)
+	type T2 chan [unsafe.Sizeof(func(ch T2){ _ = <-ch })]byte
+	type T3 /* ERROR invalid recursive type */ = chan [unsafe.Sizeof(func(ch T3){ _ = <-ch })]byte
+}
diff --git a/src/internal/types/testdata/check/cycles1.go b/src/internal/types/testdata/check/cycles1.go
new file mode 100644
index 0000000..ae2b38e
--- /dev/null
+++ b/src/internal/types/testdata/check/cycles1.go
@@ -0,0 +1,77 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type (
+	A interface {
+		a() interface {
+			ABC1
+		}
+	}
+	B interface {
+		b() interface {
+			ABC2
+		}
+	}
+	C interface {
+		c() interface {
+			ABC3
+		}
+	}
+
+	AB interface {
+		A
+		B
+	}
+	BC interface {
+		B
+		C
+	}
+
+	ABC1 interface {
+		A
+		B
+		C
+	}
+	ABC2 interface {
+		AB
+		C
+	}
+	ABC3 interface {
+		A
+		BC
+	}
+)
+
+var (
+	x1 ABC1
+	x2 ABC2
+	x3 ABC3
+)
+
+func _() {
+	// all types have the same method set
+	x1 = x2
+	x2 = x1
+
+	x1 = x3
+	x3 = x1
+
+	x2 = x3
+	x3 = x2
+
+	// all methods return the same type again
+	x1 = x1.a()
+	x1 = x1.b()
+	x1 = x1.c()
+
+	x2 = x2.a()
+	x2 = x2.b()
+	x2 = x2.c()
+
+	x3 = x3.a()
+	x3 = x3.b()
+	x3 = x3.c()
+}
diff --git a/src/internal/types/testdata/check/cycles2.go b/src/internal/types/testdata/check/cycles2.go
new file mode 100644
index 0000000..8480b29
--- /dev/null
+++ b/src/internal/types/testdata/check/cycles2.go
@@ -0,0 +1,98 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "unsafe"
+
+// Test case for issue 5090
+
+type t interface {
+	f(u)
+}
+
+type u interface {
+	t
+}
+
+func _() {
+	var t t
+	var u u
+
+	t.f(t)
+	t.f(u)
+
+	u.f(t)
+	u.f(u)
+}
+
+
+// Test case for issues #6589, #33656.
+
+type A interface {
+	a() interface {
+		AB
+	}
+}
+
+type B interface {
+	b() interface {
+		AB
+	}
+}
+
+type AB interface {
+	a() interface {
+		A
+		B
+	}
+	b() interface {
+		A
+		B
+	}
+}
+
+var x AB
+var y interface {
+	A
+	B
+}
+
+var _ = x == y
+
+
+// Test case for issue 6638.
+
+type T interface {
+	m() [T(nil).m /* ERROR undefined */ ()[0]]int
+}
+
+// Variations of this test case.
+
+type T1 /* ERROR invalid recursive type */ interface {
+	m() [x1.m()[0]]int
+}
+
+var x1 T1
+
+type T2 /* ERROR invalid recursive type */ interface {
+	m() [len(x2.m())]int
+}
+
+var x2 T2
+
+type T3 /* ERROR invalid recursive type */ interface {
+	m() [unsafe.Sizeof(x3.m)]int
+}
+
+var x3 T3
+
+type T4 /* ERROR invalid recursive type */ interface {
+	m() [unsafe.Sizeof(cast4(x4.m))]int // cast is invalid but we have a cycle, so all bets are off
+}
+
+var x4 T4
+var _ = cast4(x4.m)
+
+type cast4 func()
diff --git a/src/internal/types/testdata/check/cycles3.go b/src/internal/types/testdata/check/cycles3.go
new file mode 100644
index 0000000..4330551
--- /dev/null
+++ b/src/internal/types/testdata/check/cycles3.go
@@ -0,0 +1,60 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "unsafe"
+
+var (
+	_ A = A(nil).a().b().c().d().e().f()
+	_ A = A(nil).b().c().d().e().f()
+	_ A = A(nil).c().d().e().f()
+	_ A = A(nil).d().e().f()
+	_ A = A(nil).e().f()
+	_ A = A(nil).f()
+	_ A = A(nil)
+)
+
+type (
+	A interface {
+		a() B
+		B
+	}
+
+	B interface {
+		b() C
+		C
+	}
+
+	C interface {
+		c() D
+		D
+	}
+
+	D interface {
+		d() E
+		E
+	}
+
+	E interface {
+		e() F
+		F
+	}
+
+	F interface {
+		f() A
+	}
+)
+
+type (
+	U /* ERROR invalid recursive type */ interface {
+		V
+	}
+
+	V interface {
+		v() [unsafe.Sizeof(u)]int
+	}
+)
+
+var u U
diff --git a/src/internal/types/testdata/check/cycles4.go b/src/internal/types/testdata/check/cycles4.go
new file mode 100644
index 0000000..924aabf
--- /dev/null
+++ b/src/internal/types/testdata/check/cycles4.go
@@ -0,0 +1,121 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "unsafe"
+
+// Check that all methods of T are collected before
+// determining the result type of m (which embeds
+// all methods of T).
+
+type T interface {
+	m() interface {T}
+	E
+}
+
+var _ int = T.m(nil).m().e()
+
+type E interface {
+	e() int
+}
+
+// Check that unresolved forward chains are followed
+// (see also comment in resolver.go, checker.typeDecl).
+
+var _ int = C.m(nil).m().e()
+
+type A B
+
+type B interface {
+	m() interface{C}
+	E
+}
+
+type C A
+
+// Check that interface type comparison for identity
+// does not recur endlessly.
+
+type T1 interface {
+	m() interface{T1}
+}
+
+type T2 interface {
+	m() interface{T2}
+}
+
+func _(x T1, y T2) {
+	// Checking for assignability of interfaces must check
+	// if all methods of x are present in y, and that they
+	// have identical signatures. The signatures recur via
+	// the result type, which is an interface that embeds
+	// a single method m that refers to the very interface
+	// that contains it. This requires cycle detection in
+	// identity checks for interface types.
+	x = y
+}
+
+type T3 interface {
+	m() interface{T4}
+}
+
+type T4 interface {
+	m() interface{T3}
+}
+
+func _(x T1, y T3) {
+	x = y
+}
+
+// Check that interfaces are type-checked in order of
+// (embedded interface) dependencies (was issue 7158).
+
+var x1 T5 = T7(nil)
+
+type T5 interface {
+	T6
+}
+
+type T6 interface {
+	m() T7
+}
+type T7 interface {
+	T5
+}
+
+// Actual test case from issue 7158.
+
+func wrapNode() Node {
+	return wrapElement()
+}
+
+func wrapElement() Element {
+	return nil
+}
+
+type EventTarget interface {
+	AddEventListener(Event)
+}
+
+type Node interface {
+	EventTarget
+}
+
+type Element interface {
+	Node
+}
+
+type Event interface {
+	Target() Element
+}
+
+// Check that accessing an interface method too early doesn't lead
+// to follow-on errors due to an incorrectly computed type set.
+
+type T8 interface {
+	m() [unsafe.Sizeof(T8.m /* ERROR undefined */ )]int
+}
+
+var _ = T8.m // no error expected here
diff --git a/src/internal/types/testdata/check/cycles5.go b/src/internal/types/testdata/check/cycles5.go
new file mode 100644
index 0000000..5e0d191
--- /dev/null
+++ b/src/internal/types/testdata/check/cycles5.go
@@ -0,0 +1,200 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "unsafe"
+
+// test case from issue #18395
+
+type (
+	A interface { B }
+	B interface { C }
+	C interface { D; F() A }
+	D interface { G() B }
+)
+
+var _ = A(nil).G // G must be found
+
+
+// test case from issue #21804
+
+type sourceBridge interface {
+	listVersions() ([]Version, error)
+}
+
+type Constraint interface {
+	copyTo(*ConstraintMsg)
+}
+
+type ConstraintMsg struct{}
+
+func (m *ConstraintMsg) asUnpairedVersion() UnpairedVersion {
+	return nil
+}
+
+type Version interface {
+	Constraint
+}
+
+type UnpairedVersion interface {
+	Version
+}
+
+var _ Constraint = UnpairedVersion(nil)
+
+
+// derived test case from issue #21804
+
+type (
+	_ interface{ m(B1) }
+	A1 interface{ a(D1) }
+	B1 interface{ A1 }
+	C1 interface{ B1 }
+	D1 interface{ C1 }
+)
+
+var _ A1 = C1(nil)
+
+
+// derived test case from issue #22701
+
+func F(x I4) interface{} {
+	return x.Method()
+}
+
+type Unused interface {
+	RefersToI1(a I1)
+}
+
+type I1 interface {
+	I2
+	I3
+}
+
+type I2 interface {
+	RefersToI4() I4
+}
+
+type I3 interface {
+	Method() interface{}
+}
+
+type I4 interface {
+	I1
+}
+
+
+// check embedding of error interface
+
+type Error interface{ error }
+
+var err Error
+var _ = err.Error()
+
+
+// more esoteric cases
+
+type (
+	T1 interface { T2 }
+	T2 /* ERROR invalid recursive type */ T2
+)
+
+type (
+	T3 interface { T4 }
+	T4 /* ERROR invalid recursive type */ T5
+	T5 = T6
+	T6 = T7
+	T7 = T4
+)
+
+
+// arbitrary code may appear inside an interface
+
+const n = unsafe.Sizeof(func(){})
+
+type I interface {
+	m([unsafe.Sizeof(func() { I.m(nil, [n]byte{}) })]byte)
+}
+
+
+// test cases for varias alias cycles
+
+type T10 /* ERROR invalid recursive type */ = *T10                 // issue #25141
+type T11 /* ERROR invalid recursive type */ = interface{ f(T11) }  // issue #23139
+
+// issue #18640
+type (
+	aa = bb
+	bb struct {
+		*aa
+	}
+)
+
+type (
+	a struct{ *b }
+	b = c
+	c struct{ *b /* ERROR invalid use of type alias */ }
+)
+
+// issue #24939
+type (
+	_ interface {
+		M(P)
+	}
+
+	M interface {
+		F() P // ERROR invalid use of type alias
+	}
+
+	P = interface {
+		I() M
+	}
+)
+
+// issue #8699
+type T12 /* ERROR invalid recursive type */ [len(a12)]int
+var a12 = makeArray()
+func makeArray() (res T12) { return }
+
+// issue #20770
+var r /* ERROR invalid cycle in declaration of r */ = newReader()
+func newReader() r
+
+// variations of the theme of #8699 and #20770
+var arr /* ERROR cycle */ = f()
+func f() [len(arr)]int
+
+// issue #25790
+func ff(ff /* ERROR not a type */ )
+func gg((gg /* ERROR not a type */ ))
+
+type T13 /* ERROR invalid recursive type T13 */ [len(b13)]int
+var b13 T13
+
+func g1() [unsafe.Sizeof(g1)]int
+func g2() [unsafe.Sizeof(x2)]int
+var x2 = g2
+
+// verify that we get the correct sizes for the functions above
+// (note: assert is statically evaluated in go/types test mode)
+func init() {
+	assert(unsafe.Sizeof(g1) == 8)
+	assert(unsafe.Sizeof(x2) == 8)
+}
+
+func h() [h /* ERROR no value */ ()[0]]int { panic(0) }
+
+var c14 /* ERROR cycle */ T14
+type T14 [uintptr(unsafe.Sizeof(&c14))]byte
+
+// issue #34333
+type T15 /* ERROR invalid recursive type T15 */ struct {
+	f func() T16
+	b T16
+}
+
+type T16 struct {
+	T15
+}
\ No newline at end of file
diff --git a/src/internal/types/testdata/check/decls0.go b/src/internal/types/testdata/check/decls0.go
new file mode 100644
index 0000000..868b318
--- /dev/null
+++ b/src/internal/types/testdata/check/decls0.go
@@ -0,0 +1,210 @@
+// -lang=go1.17
+
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// type declarations
+
+package p // don't permit non-interface elements in interfaces
+
+import "unsafe"
+
+const pi = 3.1415
+
+type (
+	N undefined /* ERROR "undefined" */
+	B bool
+	I int32
+	A [10]P
+	T struct {
+		x, y P
+	}
+	P *T
+	R (*R)
+	F func(A) I
+	Y interface {
+		f(A) I
+	}
+	S [](((P)))
+	M map[I]F
+	C chan<- I
+
+	// blank types must be typechecked
+	_ pi /* ERROR "not a type" */
+	_ struct{}
+	_ struct{ pi /* ERROR "not a type" */ }
+)
+
+
+// declarations of init
+const _, init /* ERROR "cannot declare init" */ , _ = 0, 1, 2
+type init /* ERROR "cannot declare init" */ struct{}
+var _, init /* ERROR "cannot declare init" */ int
+
+func init() {}
+func init /* ERROR "missing function body" */ ()
+
+func _() { const init = 0 }
+func _() { type init int }
+func _() { var init int; _ = init }
+
+// invalid array types
+type (
+	iA0 [... /* ERROR "invalid use of \[...\] array" */ ]byte
+	// The error message below could be better. At the moment
+	// we believe an integer that is too large is not an integer.
+	// But at least we get an error.
+	iA1 [1 /* ERROR "must be integer" */ <<100]int
+	iA2 [- /* ERROR "invalid array length" */ 1]complex128
+	iA3 ["foo" /* ERROR "must be integer" */ ]string
+	iA4 [float64 /* ERROR "must be integer" */ (0)]int
+)
+
+
+type (
+	p1 pi.foo /* ERROR "pi.foo is not a type" */
+	p2 unsafe.Pointer
+)
+
+
+type (
+	Pi pi /* ERROR "not a type" */
+
+	a /* ERROR "invalid recursive type" */ a
+	a /* ERROR "redeclared" */ int
+
+	b /* ERROR "invalid recursive type" */ c
+	c d
+	d e
+	e b
+
+	t *t
+
+	U V
+	V *W
+	W U
+
+	P1 *S2
+	P2 P1
+
+	S0 struct {
+	}
+	S1 struct {
+		a, b, c int
+		u, v, a /* ERROR "redeclared" */ float32
+	}
+	S2 struct {
+		S0 // embedded field
+		S0 /* ERROR "redeclared" */ int
+	}
+	S3 struct {
+		x S2
+	}
+	S4/* ERROR "invalid recursive type" */ struct {
+		S4
+	}
+	S5 /* ERROR "invalid recursive type" */ struct {
+		S6
+	}
+	S6 struct {
+		field S7
+	}
+	S7 struct {
+		S5
+	}
+
+	L1 []L1
+	L2 []int
+
+	A1 [10.0]int
+	A2 /* ERROR "invalid recursive type" */ [10]A2
+	A3 /* ERROR "invalid recursive type" */ [10]struct {
+		x A4
+	}
+	A4 [10]A3
+
+	F1 func()
+	F2 func(x, y, z float32)
+	F3 func(x, y, x /* ERROR "redeclared" */ float32)
+	F4 func() (x, y, x /* ERROR "redeclared" */ float32)
+	F5 func(x int) (x /* ERROR "redeclared" */ float32)
+	F6 func(x ...int)
+
+	I1 interface{}
+	I2 interface {
+		m1()
+	}
+	I3 interface {
+		m1()
+		m1 /* ERROR "duplicate method" */ ()
+	}
+	I4 interface {
+		m1(x, y, x /* ERROR "redeclared" */ float32)
+		m2() (x, y, x /* ERROR "redeclared" */ float32)
+		m3(x int) (x /* ERROR "redeclared" */ float32)
+	}
+	I5 interface {
+		m1(I5)
+	}
+	I6 interface {
+		S0 /* ERROR "non-interface type S0" */
+	}
+	I7 interface {
+		I1
+		I1
+	}
+	I8 /* ERROR "invalid recursive type" */ interface {
+		I8
+	}
+	I9 /* ERROR "invalid recursive type" */ interface {
+		I10
+	}
+	I10 interface {
+		I11
+	}
+	I11 interface {
+		I9
+	}
+
+	C1 chan int
+	C2 <-chan int
+	C3 chan<- C3
+	C4 chan C5
+	C5 chan C6
+	C6 chan C4
+
+	M1 map[Last]string
+	M2 map[string]M2
+
+	Last int
+)
+
+// cycles in function/method declarations
+// (test cases for issues #5217, #25790 and variants)
+func f1(x f1 /* ERROR "not a type" */ ) {}
+func f2(x *f2 /* ERROR "not a type" */ ) {}
+func f3() (x f3 /* ERROR "not a type" */ ) { return }
+func f4() (x *f4 /* ERROR "not a type" */ ) { return }
+// TODO(#43215) this should be detected as a cycle error
+func f5([unsafe.Sizeof(f5)]int) {}
+
+func (S0) m1 (x S0.m1 /* ERROR S0.m1 is not a type */ ) {}
+func (S0) m2 (x *S0.m2 /* ERROR S0.m2 is not a type */ ) {}
+func (S0) m3 () (x S0.m3 /* ERROR S0.m3 is not a type */ ) { return }
+func (S0) m4 () (x *S0.m4 /* ERROR S0.m4 is not a type */ ) { return }
+
+// interfaces may not have any blank methods
+type BlankI interface {
+	_ /* ERROR "methods must have a unique non-blank name" */ ()
+	_ /* ERROR "methods must have a unique non-blank name" */ (float32) int
+	m()
+}
+
+// non-interface types may have multiple blank methods
+type BlankT struct{}
+
+func (BlankT) _() {}
+func (BlankT) _(int) {}
+func (BlankT) _() int { return 0 }
+func (BlankT) _(int) int { return 0}
diff --git a/src/internal/types/testdata/check/decls1.go b/src/internal/types/testdata/check/decls1.go
new file mode 100644
index 0000000..b232fc8
--- /dev/null
+++ b/src/internal/types/testdata/check/decls1.go
@@ -0,0 +1,146 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// variable declarations
+
+package decls1
+
+import (
+	"math"
+)
+
+// Global variables without initialization
+var (
+	a, b bool
+	c byte
+	d uint8
+	r rune
+	i int
+	j, k, l int
+	x, y float32
+	xx, yy float64
+	u, v complex64
+	uu, vv complex128
+	s, t string
+	array []byte
+	iface interface{}
+
+	blank _ /* ERROR "cannot use _" */
+)
+
+// Global variables with initialization
+var (
+	s1 = i + j
+	s2 = i /* ERROR "mismatched types" */ + x
+	s3 = c + d
+	s4 = s + t
+	s5 = s /* ERROR "invalid operation" */ / t
+	s6 = array[t1]
+	s7 = array[x /* ERROR "integer" */]
+	s8 = &a
+	s10 = &42 /* ERROR "cannot take address" */
+	s11 = &v
+	s12 = -(u + *t11) / *&v
+	s13 = a /* ERROR "shifted operand" */ << d
+	s14 = i << j
+	s18 = math.Pi * 10.0
+	s19 = s1 /* ERROR "cannot call" */ ()
+ 	s20 = f0 /* ERROR "no value" */ ()
+	s21 = f6(1, s1, i)
+	s22 = f6(1, s1, uu /* ERROR "cannot use .* in argument" */ )
+
+	t1 int = i + j
+	t2 int = i /* ERROR "mismatched types" */ + x
+	t3 int = c /* ERROR "cannot use .* variable declaration" */ + d
+	t4 string = s + t
+	t5 string = s /* ERROR "invalid operation" */ / t
+	t6 byte = array[t1]
+	t7 byte = array[x /* ERROR "must be integer" */]
+	t8 *int = & /* ERROR "cannot use .* variable declaration" */ a
+	t10 *int = &42 /* ERROR "cannot take address" */
+	t11 *complex64 = &v
+	t12 complex64 = -(u + *t11) / *&v
+	t13 int = a /* ERROR "shifted operand" */ << d
+	t14 int = i << j
+	t15 math /* ERROR "not in selector" */
+	t16 math.xxx /* ERROR "undefined" */
+	t17 math /* ERROR "not a type" */ .Pi
+	t18 float64 = math.Pi * 10.0
+	t19 int = t1 /* ERROR "cannot call" */ ()
+	t20 int = f0 /* ERROR "no value" */ ()
+	t21 int = a /* ERROR "cannot use .* variable declaration" */
+)
+
+// Various more complex expressions
+var (
+	u1 = x /* ERROR "not an interface" */ .(int)
+	u2 = iface.([]int)
+	u3 = iface.(a /* ERROR "not a type" */ )
+	u4, ok = iface.(int)
+	u5, ok2, ok3 = iface /* ERROR "assignment mismatch" */ .(int)
+)
+
+// Constant expression initializations
+var (
+	v1 = 1 /* ERROR "mismatched types untyped int and untyped string" */ + "foo"
+	v2 = c + 255
+	v3 = c + 256 /* ERROR "overflows" */
+	v4 = r + 2147483647
+	v5 = r + 2147483648 /* ERROR "overflows" */
+	v6 = 42
+	v7 = v6 + 9223372036854775807
+	v8 = v6 + 9223372036854775808 /* ERROR "overflows" */
+	v9 = i + 1 << 10
+	v10 byte = 1024 /* ERROR "overflows" */
+	v11 = xx/yy*yy - xx
+	v12 = true && false
+	v13 = nil /* ERROR "use of untyped nil" */
+	v14 string = 257 // ERROR cannot use 257 .* as string value in variable declaration$
+	v15 int8 = 257 // ERROR cannot use 257 .* as int8 value in variable declaration .*overflows
+)
+
+// Multiple assignment expressions
+var (
+	m1a, m1b = 1, 2
+	m2a, m2b, m2c /* ERROR "missing init expr for m2c" */ = 1, 2
+	m3a, m3b = 1, 2, 3 /* ERROR "extra init expr 3" */
+)
+
+func _() {
+	var (
+		m1a, m1b = 1, 2
+		m2a, m2b, m2c /* ERROR "missing init expr for m2c" */ = 1, 2
+		m3a, m3b = 1, 2, 3 /* ERROR "extra init expr 3" */
+	)
+
+	_, _ = m1a, m1b
+	_, _, _ = m2a, m2b, m2c
+	_, _ = m3a, m3b
+}
+
+// Declaration of parameters and results
+func f0() {}
+func f1(a /* ERROR "not a type" */) {}
+func f2(a, b, c d /* ERROR "not a type" */) {}
+
+func f3() int { return 0 }
+func f4() a /* ERROR "not a type" */ { return 0 }
+func f5() (a, b, c d /* ERROR "not a type" */) { return }
+
+func f6(a, b, c int) complex128 { return 0 }
+
+// Declaration of receivers
+type T struct{}
+
+func (T) m0() {}
+func (*T) m1() {}
+func (x T) m2() {}
+func (x *T) m3() {}
+
+// Initialization functions
+func init() {}
+func init /* ERROR "no arguments and no return values" */ (int) {}
+func init /* ERROR "no arguments and no return values" */ () int { return 0 }
+func init /* ERROR "no arguments and no return values" */ (int) int { return 0 }
+func (T) init(int) int { return 0 }
diff --git a/src/internal/types/testdata/check/decls2/decls2a.go b/src/internal/types/testdata/check/decls2/decls2a.go
new file mode 100644
index 0000000..731405b
--- /dev/null
+++ b/src/internal/types/testdata/check/decls2/decls2a.go
@@ -0,0 +1,111 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// method declarations
+
+package decls2
+
+import "time"
+import "unsafe"
+
+// T1 declared before its methods.
+type T1 struct{
+	f int
+}
+
+func (T1) m() {}
+func (T1) m /* ERROR "already declared" */ () {}
+func (x *T1) f /* ERROR "field and method" */ () {}
+
+// Conflict between embedded field and method name,
+// with the embedded field being a basic type.
+type T1b struct {
+	int
+}
+
+func (T1b) int /* ERROR "field and method" */ () {}
+
+type T1c struct {
+	time.Time
+}
+
+func (T1c) Time /* ERROR "field and method" */ () int { return 0 }
+
+// Disabled for now: LookupFieldOrMethod will find Pointer even though
+// it's double-declared (it would cost extra in the common case to verify
+// this). But the MethodSet computation will not find it due to the name
+// collision caused by the double-declaration, leading to an internal
+// inconsistency while we are verifying one computation against the other.
+// var _ = T1c{}.Pointer
+
+// T2's method declared before the type.
+func (*T2) f /* ERROR "field and method" */ () {}
+
+type T2 struct {
+	f int
+}
+
+// Methods declared without a declared type.
+func (undefined /* ERROR "undefined" */) m() {}
+func (x *undefined /* ERROR "undefined" */) m() {}
+
+func (pi /* ERROR "not a type" */) m1() {}
+func (x pi /* ERROR "not a type" */) m2() {}
+func (x *pi /* ERROR "not a type" */ ) m3() {}
+
+// Blank types.
+type _ struct { m int }
+type _ struct { m int }
+
+func (_ /* ERROR "cannot use _" */) m() {}
+func m(_ /* ERROR "cannot use _" */) {}
+
+// Methods with receiver base type declared in another file.
+func (T3) m1() {}
+func (*T3) m2() {}
+func (x T3) m3() {}
+func (x *T3) f /* ERROR "field and method" */ () {}
+
+// Methods of non-struct type.
+type T4 func()
+
+func (self T4) m() func() { return self }
+
+// Methods associated with an interface.
+type T5 interface {
+	m() int
+}
+
+func (T5 /* ERROR "invalid receiver" */ ) m1() {}
+func (T5 /* ERROR "invalid receiver" */ ) m2() {}
+
+// Methods associated with a named pointer type.
+type ptr *int
+func (ptr /* ERROR "invalid receiver" */ ) _() {}
+func (* /* ERROR "invalid receiver" */ ptr) _() {}
+
+// Methods with zero or multiple receivers.
+func ( /* ERROR "method has no receiver" */ ) _() {}
+func (T3, * /* ERROR "method has multiple receivers" */ T3) _() {}
+func (T3, T3, T3 /* ERROR "method has multiple receivers" */ ) _() {}
+func (a, b /* ERROR "method has multiple receivers" */ T3) _() {}
+func (a, b, c /* ERROR "method has multiple receivers" */ T3) _() {}
+
+// Methods associated with non-local or unnamed types.
+func (int /* ERROR "cannot define new methods on non-local type int" */ ) m() {}
+func ([ /* ERROR "invalid receiver" */ ]int) m() {}
+func (time /* ERROR "cannot define new methods on non-local type time\.Time" */ .Time) m() {}
+func (* /* ERROR "cannot define new methods on non-local type time\.Time" */ time.Time) m() {}
+func (x /* ERROR "invalid receiver" */ interface{}) m() {}
+
+// Unsafe.Pointer is treated like a pointer when used as receiver type.
+type UP unsafe.Pointer
+func (UP /* ERROR "invalid" */ ) m1() {}
+func (* /* ERROR "invalid" */ UP) m2() {}
+
+// Double declarations across package files
+const c_double = 0
+type t_double int
+var v_double int
+func f_double() {}
diff --git a/src/internal/types/testdata/check/decls2/decls2b.go b/src/internal/types/testdata/check/decls2/decls2b.go
new file mode 100644
index 0000000..d4c5861
--- /dev/null
+++ b/src/internal/types/testdata/check/decls2/decls2b.go
@@ -0,0 +1,75 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// method declarations
+
+package decls2
+
+import "io"
+
+const pi = 3.1415
+
+func (T1) m /* ERROR "already declared" */ () {}
+func (T2) m(io.Writer) {}
+
+type T3 struct {
+	f *T3
+}
+
+type T6 struct {
+	x int
+}
+
+func (t *T6) m1() int {
+	return t.x
+}
+
+func f() {
+	var t *T6
+	t.m1()
+}
+
+// Double declarations across package files
+const c_double /* ERROR "redeclared" */ = 0
+type t_double  /* ERROR "redeclared" */ int
+var v_double /* ERROR "redeclared" */ int
+func f_double /* ERROR "redeclared" */ () {}
+
+// Blank methods need to be type-checked.
+// Verify by checking that errors are reported.
+func (T /* ERROR "undefined" */ ) _() {}
+func (T1) _(undefined /* ERROR "undefined" */ ) {}
+func (T1) _() int { return "foo" /* ERROR "cannot use .* in return statement" */ }
+
+// Methods with undefined receiver type can still be checked.
+// Verify by checking that errors are reported.
+func (Foo /* ERROR "undefined" */ ) m() {}
+func (Foo /* ERROR "undefined" */ ) m(undefined /* ERROR "undefined" */ ) {}
+func (Foo /* ERROR "undefined" */ ) m() int { return "foo" /* ERROR "cannot use .* in return statement" */ }
+
+func (Foo /* ERROR "undefined" */ ) _() {}
+func (Foo /* ERROR "undefined" */ ) _(undefined /* ERROR "undefined" */ ) {}
+func (Foo /* ERROR "undefined" */ ) _() int { return "foo" /* ERROR "cannot use .* in return statement" */ }
+
+// Receiver declarations are regular parameter lists;
+// receiver types may use parentheses, and the list
+// may have a trailing comma.
+type T7 struct {}
+
+func (T7) m1() {}
+func ((T7)) m2() {}
+func ((*T7)) m3() {}
+func (x *(T7),) m4() {}
+func (x (*(T7)),) m5() {}
+func (x ((*((T7)))),) m6() {}
+
+// Check that methods with parenthesized receiver are actually present (issue #23130).
+var (
+	_ = T7.m1
+	_ = T7.m2
+	_ = (*T7).m3
+	_ = (*T7).m4
+	_ = (*T7).m5
+	_ = (*T7).m6
+)
diff --git a/src/internal/types/testdata/check/decls3.go b/src/internal/types/testdata/check/decls3.go
new file mode 100644
index 0000000..01d4ffe
--- /dev/null
+++ b/src/internal/types/testdata/check/decls3.go
@@ -0,0 +1,309 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// embedded types
+
+package decls3
+
+import "unsafe"
+import "fmt"
+
+// fields with the same name at the same level cancel each other out
+
+func _() {
+	type (
+		T1 struct { X int }
+		T2 struct { X int }
+		T3 struct { T1; T2 } // X is embedded twice at the same level via T1->X, T2->X
+	)
+
+	var t T3
+	_ = t.X /* ERROR "ambiguous selector t.X" */
+}
+
+func _() {
+	type (
+		T1 struct { X int }
+		T2 struct { T1 }
+		T3 struct { T1 }
+		T4 struct { T2; T3 } // X is embedded twice at the same level via T2->T1->X, T3->T1->X
+	)
+
+	var t T4
+	_ = t.X /* ERROR "ambiguous selector t.X" */
+}
+
+func issue4355() {
+	type (
+	    T1 struct {X int}
+	    T2 struct {T1}
+	    T3 struct {T2}
+	    T4 struct {T2}
+	    T5 struct {T3; T4} // X is embedded twice at the same level via T3->T2->T1->X, T4->T2->T1->X
+	)
+
+	var t T5
+	_ = t.X /* ERROR "ambiguous selector t.X" */
+}
+
+func _() {
+	type State int
+	type A struct{ State }
+	type B struct{ fmt.State }
+	type T struct{ A; B }
+
+	var t T
+	_ = t.State /* ERROR "ambiguous selector t.State" */
+}
+
+// Embedded fields can be predeclared types.
+
+func _() {
+	type T0 struct{
+		int
+		float32
+		f int
+	}
+	var x T0
+	_ = x.int
+	_ = x.float32
+	_ = x.f
+
+	type T1 struct{
+		T0
+	}
+	var y T1
+	_ = y.int
+	_ = y.float32
+	_ = y.f
+}
+
+// Restrictions on embedded field types.
+
+func _() {
+	type I1 interface{}
+	type I2 interface{}
+	type P1 *int
+	type P2 *int
+	type UP unsafe.Pointer
+
+	type T1 struct {
+		I1
+		* /* ERROR "cannot be a pointer to an interface" */ I2
+		* /* ERROR "cannot be a pointer to an interface" */ error
+		P1 /* ERROR "cannot be a pointer" */
+		* /* ERROR "cannot be a pointer" */ P2
+	}
+
+	// unsafe.Pointers are treated like regular pointers when embedded
+	type T2 struct {
+		unsafe /* ERROR "cannot be unsafe.Pointer" */ .Pointer
+		*/* ERROR "cannot be unsafe.Pointer" */ /* ERROR "Pointer redeclared" */ unsafe.Pointer
+		UP /* ERROR "cannot be unsafe.Pointer" */
+		* /* ERROR "cannot be unsafe.Pointer" */  /* ERROR "UP redeclared" */ UP
+	}
+}
+
+// Named types that are pointers.
+
+type S struct{ x int }
+func (*S) m() {}
+type P *S
+
+func _() {
+	var s *S
+	_ = s.x
+	_ = s.m
+
+	var p P
+	_ = p.x
+	_ = p.m /* ERROR "no field or method" */
+	_ = P.m /* ERROR "no field or method" */
+}
+
+// Borrowed from the FieldByName test cases in reflect/all_test.go.
+
+type D1 struct {
+	d int
+}
+type D2 struct {
+	d int
+}
+
+type S0 struct {
+	A, B, C int
+	D1
+	D2
+}
+
+type S1 struct {
+	B int
+	S0
+}
+
+type S2 struct {
+	A int
+	*S1
+}
+
+type S1x struct {
+	S1
+}
+
+type S1y struct {
+	S1
+}
+
+type S3 struct {
+	S1x
+	S2
+	D, E int
+	*S1y
+}
+
+type S4 struct {
+	*S4
+	A int
+}
+
+// The X in S6 and S7 annihilate, but they also block the X in S8.S9.
+type S5 struct {
+	S6
+	S7
+	S8
+}
+
+type S6 struct {
+	X int
+}
+
+type S7 S6
+
+type S8 struct {
+	S9
+}
+
+type S9 struct {
+	X int
+	Y int
+}
+
+// The X in S11.S6 and S12.S6 annihilate, but they also block the X in S13.S8.S9.
+type S10 struct {
+	S11
+	S12
+	S13
+}
+
+type S11 struct {
+	S6
+}
+
+type S12 struct {
+	S6
+}
+
+type S13 struct {
+	S8
+}
+
+func _() {
+	_ = struct{}{}.Foo /* ERROR "no field or method" */
+	_ = S0{}.A
+	_ = S0{}.D /* ERROR "no field or method" */
+	_ = S1{}.A
+	_ = S1{}.B
+	_ = S1{}.S0
+	_ = S1{}.C
+	_ = S2{}.A
+	_ = S2{}.S1
+	_ = S2{}.B
+	_ = S2{}.C
+	_ = S2{}.D /* ERROR "no field or method" */
+	_ = S3{}.S1 /* ERROR "ambiguous selector S3{}.S1" */
+	_ = S3{}.A
+	_ = S3{}.B /* ERROR "ambiguous selector" S3{}.B */
+	_ = S3{}.D
+	_ = S3{}.E
+	_ = S4{}.A
+	_ = S4{}.B /* ERROR "no field or method" */
+	_ = S5{}.X /* ERROR "ambiguous selector S5{}.X" */
+	_ = S5{}.Y
+	_ = S10{}.X /* ERROR "ambiguous selector S10{}.X" */
+	_ = S10{}.Y
+}
+
+// Borrowed from the FieldByName benchmark in reflect/all_test.go.
+
+type R0 struct {
+	*R1
+	*R2
+	*R3
+	*R4
+}
+
+type R1 struct {
+	*R5
+	*R6
+	*R7
+	*R8
+}
+
+type R2 R1
+type R3 R1
+type R4 R1
+
+type R5 struct {
+	*R9
+	*R10
+	*R11
+	*R12
+}
+
+type R6 R5
+type R7 R5
+type R8 R5
+
+type R9 struct {
+	*R13
+	*R14
+	*R15
+	*R16
+}
+
+type R10 R9
+type R11 R9
+type R12 R9
+
+type R13 struct {
+	*R17
+	*R18
+	*R19
+	*R20
+}
+
+type R14 R13
+type R15 R13
+type R16 R13
+
+type R17 struct {
+	*R21
+	*R22
+	*R23
+	*R24
+}
+
+type R18 R17
+type R19 R17
+type R20 R17
+
+type R21 struct {
+	X int
+}
+
+type R22 R21
+type R23 R21
+type R24 R21
+
+var _ = R0{}.X /* ERROR "ambiguous selector R0{}.X" */
\ No newline at end of file
diff --git a/src/internal/types/testdata/check/decls4.go b/src/internal/types/testdata/check/decls4.go
new file mode 100644
index 0000000..c1294ee
--- /dev/null
+++ b/src/internal/types/testdata/check/decls4.go
@@ -0,0 +1,199 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// type aliases
+
+package decls4
+
+type (
+	T0 [10]int
+	T1 []byte
+	T2 struct {
+		x int
+	}
+	T3 interface{
+		m() T2
+	}
+	T4 func(int, T0) chan T2
+)
+
+type (
+	Ai = int
+	A0 = T0
+	A1 = T1
+	A2 = T2
+	A3 = T3
+	A4 = T4
+
+	A10 = [10]int
+	A11 = []byte
+	A12 = struct {
+		x int
+	}
+	A13 = interface{
+		m() A2
+	}
+	A14 = func(int, A0) chan A2
+)
+
+// check assignment compatibility due to equality of types
+var (
+	xi_ int
+	ai Ai = xi_
+
+	x0 T0
+	a0 A0 = x0
+
+	x1 T1
+	a1 A1 = x1
+
+	x2 T2
+	a2 A2 = x2
+
+	x3 T3
+	a3 A3 = x3
+
+	x4 T4
+	a4 A4 = x4
+)
+
+// alias receiver types
+func (Ai /* ERROR "cannot define new methods on non-local type int" */) m1() {}
+func (T0) m1() {}
+func (A0) m1 /* ERROR already declared */ () {}
+func (A0) m2 () {}
+func (A3 /* ERROR invalid receiver */ ) m1 () {}
+func (A10 /* ERROR invalid receiver */ ) m1() {}
+
+// x0 has methods m1, m2 declared via receiver type names T0 and A0
+var _ interface{ m1(); m2() } = x0
+
+// alias receiver types (test case for issue #23042)
+type T struct{}
+
+var (
+	_ = T.m
+	_ = T{}.m
+	_ interface{m()} = T{}
+)
+
+var (
+	_ = T.n
+	_ = T{}.n
+	_ interface{m(); n()} = T{}
+)
+
+type U = T
+func (U) m() {}
+
+// alias receiver types (long type declaration chains)
+type (
+	V0 = V1
+	V1 = (V2)
+	V2 = ((V3))
+	V3 = T
+)
+
+func (V0) m /* ERROR already declared */ () {}
+func (V1) n() {}
+
+// alias receiver types (invalid due to cycles)
+type (
+	W0 /* ERROR invalid recursive type */ = W1
+	W1 = (W2)
+	W2 = ((W0))
+)
+
+func (W0) m() {} // no error expected (due to above cycle error)
+func (W1) n() {}
+
+// alias receiver types (invalid due to builtin underlying type)
+type (
+	B0 = B1
+	B1 = B2
+	B2 = int
+)
+
+func (B0 /* ERROR cannot define new methods on non-local type int */ ) m() {}
+func (B1 /* ERROR cannot define new methods on non-local type int */ ) n() {}
+
+// cycles
+type (
+	C2 /* ERROR invalid recursive type */ = C2
+	C3 /* ERROR invalid recursive type */ = C4
+	C4 = C3
+	C5 struct {
+		f *C6
+	}
+	C6 = C5
+	C7 /* ERROR invalid recursive type */  struct {
+		f C8
+	}
+	C8 = C7
+)
+
+// embedded fields
+var (
+	s0 struct { T0 }
+	s1 struct { A0 } = s0 /* ERROR cannot use */ // embedded field names are different
+)
+
+// embedding and lookup of fields and methods
+func _(s struct{A0}) { s.A0 = x0 }
+
+type eX struct{xf int}
+
+func (eX) xm()
+
+type eY = struct{eX} // field/method set of eY includes xf, xm
+
+type eZ = *struct{eX} // field/method set of eZ includes xf, xm
+
+type eA struct {
+	eX // eX contributes xf, xm to eA
+}
+
+type eA2 struct {
+	*eX // *eX contributes xf, xm to eA
+}
+
+type eB struct {
+	eY // eY contributes xf, xm to eB
+}
+
+type eB2 struct {
+	*eY // *eY contributes xf, xm to eB
+}
+
+type eC struct {
+	eZ // eZ contributes xf, xm to eC
+}
+
+var (
+	_ = eA{}.xf
+	_ = eA{}.xm
+	_ = eA2{}.xf
+	_ = eA2{}.xm
+	_ = eB{}.xf
+	_ = eB{}.xm
+	_ = eB2{}.xf
+	_ = eB2{}.xm
+	_ = eC{}.xf
+	_ = eC{}.xm
+)
+
+// ambiguous selectors due to embedding via type aliases
+type eD struct {
+	eY
+	eZ
+}
+
+var (
+	_ = eD{}.xf /* ERROR ambiguous selector eD{}.xf */
+	_ = eD{}.xm /* ERROR ambiguous selector eD{}.xm */
+)
+
+var (
+	_ interface{ xm() } = eD /* ERROR missing method xm */ {}
+)
\ No newline at end of file
diff --git a/src/internal/types/testdata/check/decls5.go b/src/internal/types/testdata/check/decls5.go
new file mode 100644
index 0000000..88d3194
--- /dev/null
+++ b/src/internal/types/testdata/check/decls5.go
@@ -0,0 +1,10 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+// declarations of main
+const _, main /* ERROR "cannot declare main" */ , _ = 0, 1, 2
+type main /* ERROR "cannot declare main" */ struct{}
+var _, main /* ERROR "cannot declare main" */ int
diff --git a/src/internal/types/testdata/check/errors.go b/src/internal/types/testdata/check/errors.go
new file mode 100644
index 0000000..b3ab8af
--- /dev/null
+++ b/src/internal/types/testdata/check/errors.go
@@ -0,0 +1,66 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package errors
+
+// Testing precise operand formatting in error messages
+// (matching messages are regular expressions, hence the \'s).
+func f(x int, m map[string]int) {
+	// no values
+	_ = f /* ERROR f\(0, m\) \(no value\) used as value */ (0, m)
+
+	// built-ins
+	_ = println // ERROR println \(built-in\) must be called
+
+	// types
+	_ = complex128 // ERROR complex128 \(type\) is not an expression
+
+	// constants
+	const c1 = 991
+	const c2 float32 = 0.5
+	const c3 = "foo"
+	0 // ERROR 0 \(untyped int constant\) is not used
+	0.5 // ERROR 0.5 \(untyped float constant\) is not used
+	"foo" // ERROR "foo" \(untyped string constant\) is not used
+	c1 // ERROR c1 \(untyped int constant 991\) is not used
+	c2 // ERROR c2 \(constant 0.5 of type float32\) is not used
+	c1 /* ERROR c1 \+ c2 \(constant 991.5 of type float32\) is not used */ + c2
+	c3 // ERROR c3 \(untyped string constant "foo"\) is not used
+
+	// variables
+	x // ERROR x \(variable of type int\) is not used
+
+	// values
+	nil // ERROR nil is not used
+	( /* ERROR \(\*int\)\(nil\) \(value of type \*int\) is not used */ *int)(nil)
+	x /* ERROR x != x \(untyped bool value\) is not used */ != x
+	x /* ERROR x \+ x \(value of type int\) is not used */ + x
+
+	// value, ok's
+	const s = "foo"
+	m /* ERROR m\[s\] \(map index expression of type int\) is not used */ [s]
+}
+
+// Valid ERROR comments can have a variety of forms.
+func _() {
+	0 /* ERROR "0 .* is not used" */
+	0 /* ERROR 0 .* is not used */
+	0 // ERROR "0 .* is not used"
+	0 // ERROR 0 .* is not used
+}
+
+// Don't report spurious errors as a consequence of earlier errors.
+// Add more tests as needed.
+func _() {
+	if err := foo /* ERROR undefined */ (); err != nil /* no error here */ {}
+}
+
+// Use unqualified names for package-local objects.
+type T struct{}
+var _ int = T /* ERROR value of type T */ {} // use T in error message rather then errors.T
+
+// Don't report errors containing "invalid type" (issue #24182).
+func _(x *missing /* ERROR undefined: missing */ ) {
+	x.m() // there shouldn't be an error here referring to *invalid type
+}
diff --git a/src/internal/types/testdata/check/expr0.go b/src/internal/types/testdata/check/expr0.go
new file mode 100644
index 0000000..dd86eca
--- /dev/null
+++ b/src/internal/types/testdata/check/expr0.go
@@ -0,0 +1,187 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// unary expressions
+
+package expr0 
+
+type mybool bool
+
+var (
+	// bool
+	b0 = true
+	b1 bool = b0
+	b2 = !true
+	b3 = !b1
+	b4 bool = !true
+	b5 bool = !b4
+	b6 = +b0 /* ERROR "not defined" */
+	b7 = -b0 /* ERROR "not defined" */
+	b8 = ^b0 /* ERROR "not defined" */
+	b9 = *b0 /* ERROR "cannot indirect" */
+	b10 = &true /* ERROR "cannot take address" */
+	b11 = &b0
+	b12 = <-b0 /* ERROR "cannot receive" */
+	b13 = & & /* ERROR "cannot take address" */ b0
+
+	// byte
+	_ = byte(0)
+	_ = byte(- /* ERROR "cannot convert" */ 1)
+	_ = - /* ERROR "-byte\(1\) \(constant -1 of type byte\) overflows byte" */ byte(1) // test for issue 11367
+	_ = byte /* ERROR "overflows byte" */ (0) - byte(1)
+
+	// int
+	i0 = 1
+	i1 int = i0
+	i2 = +1
+	i3 = +i0
+	i4 int = +1
+	i5 int = +i4
+	i6 = -1
+	i7 = -i0
+	i8 int = -1
+	i9 int = -i4
+	i10 = !i0 /* ERROR "not defined" */
+	i11 = ^1
+	i12 = ^i0
+	i13 int = ^1
+	i14 int = ^i4
+	i15 = *i0 /* ERROR "cannot indirect" */
+	i16 = &i0
+	i17 = *i16
+	i18 = <-i16 /* ERROR "cannot receive" */
+
+	// uint
+	u0 = uint(1)
+	u1 uint = u0
+	u2 = +1
+	u3 = +u0
+	u4 uint = +1
+	u5 uint = +u4
+	u6 = -1
+	u7 = -u0
+	u8 uint = - /* ERROR "overflows" */ 1
+	u9 uint = -u4
+	u10 = !u0 /* ERROR "not defined" */
+	u11 = ^1
+	u12 = ^i0
+	u13 uint = ^ /* ERROR "overflows" */ 1
+	u14 uint = ^u4
+	u15 = *u0 /* ERROR "cannot indirect" */
+	u16 = &u0
+	u17 = *u16
+	u18 = <-u16 /* ERROR "cannot receive" */
+	u19 = ^uint(0)
+
+	// float64
+	f0 = float64(1)
+	f1 float64 = f0
+	f2 = +1
+	f3 = +f0
+	f4 float64 = +1
+	f5 float64 = +f4
+	f6 = -1
+	f7 = -f0
+	f8 float64 = -1
+	f9 float64 = -f4
+	f10 = !f0 /* ERROR "not defined" */
+	f11 = ^1
+	f12 = ^i0
+	f13 float64 = ^1
+	f14 float64 = ^f4 /* ERROR "not defined" */
+	f15 = *f0 /* ERROR "cannot indirect" */
+	f16 = &f0
+	f17 = *u16
+	f18 = <-u16 /* ERROR "cannot receive" */
+
+	// complex128
+	c0 = complex128(1)
+	c1 complex128 = c0
+	c2 = +1
+	c3 = +c0
+	c4 complex128 = +1
+	c5 complex128 = +c4
+	c6 = -1
+	c7 = -c0
+	c8 complex128 = -1
+	c9 complex128 = -c4
+	c10 = !c0 /* ERROR "not defined" */
+	c11 = ^1
+	c12 = ^i0
+	c13 complex128 = ^1
+	c14 complex128 = ^c4 /* ERROR "not defined" */
+	c15 = *c0 /* ERROR "cannot indirect" */
+	c16 = &c0
+	c17 = *u16
+	c18 = <-u16 /* ERROR "cannot receive" */
+
+	// string
+	s0 = "foo"
+	s1 = +"foo" /* ERROR "not defined" */
+	s2 = -s0 /* ERROR "not defined" */
+	s3 = !s0 /* ERROR "not defined" */
+	s4 = ^s0 /* ERROR "not defined" */
+	s5 = *s4
+	s6 = &s4
+	s7 = *s6
+	s8 = <-s7
+
+	// channel
+	ch chan int
+	rc <-chan float64
+	sc chan <- string
+	ch0 = +ch /* ERROR "not defined" */
+	ch1 = -ch /* ERROR "not defined" */
+	ch2 = !ch /* ERROR "not defined" */
+	ch3 = ^ch /* ERROR "not defined" */
+	ch4 = *ch /* ERROR "cannot indirect" */
+	ch5 = &ch
+	ch6 = *ch5
+	ch7 = <-ch
+	ch8 = <-rc
+	ch9 = <-sc /* ERROR "cannot receive" */
+	ch10, ok = <-ch
+	// ok is of type bool
+	ch11, myok = <-ch
+	_ mybool = myok /* ERROR "cannot use .* in variable declaration" */
+)
+
+// address of composite literals
+type T struct{x, y int}
+
+func f() T { return T{} }
+
+var (
+	_ = &T{1, 2}
+	_ = &[...]int{}
+	_ = &[]int{}
+	_ = &[]int{}
+	_ = &map[string]T{}
+	_ = &(T{1, 2})
+	_ = &((((T{1, 2}))))
+	_ = &f /* ERROR "cannot take address" */ ()
+)
+
+// recursive pointer types
+type P *P
+
+var (
+	p1 P = new(P)
+	p2 P = *p1
+	p3 P = &p2
+)
+
+func g() (a, b int) { return }
+
+func _() {
+	_ = -g /* ERROR multiple-value g */ ()
+	_ = <-g /* ERROR multiple-value g */ ()
+}
+
+// ~ is accepted as unary operator only permitted in interface type elements
+var (
+	_ = ~ /* ERROR cannot use ~ outside of interface or type constraint */ 0
+	_ = ~ /* ERROR cannot use ~ outside of interface or type constraint */ "foo"
+	_ = ~ /* ERROR cannot use ~ outside of interface or type constraint */ i0
+)
diff --git a/src/internal/types/testdata/check/expr1.go b/src/internal/types/testdata/check/expr1.go
new file mode 100644
index 0000000..49e8bae
--- /dev/null
+++ b/src/internal/types/testdata/check/expr1.go
@@ -0,0 +1,127 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// binary expressions
+
+package expr1
+
+type mybool bool
+
+func _(x, y bool, z mybool) {
+	x = x || y
+	x = x || true
+	x = x || false
+	x = x && y
+	x = x && true
+	x = x && false
+
+	z = z /* ERROR mismatched types */ || y
+	z = z || true
+	z = z || false
+	z = z /* ERROR mismatched types */ && y
+	z = z && true
+	z = z && false
+}
+
+type myint int
+
+func _(x, y int, z myint) {
+	x = x + 1
+	x = x + 1.0
+	x = x + 1.1 // ERROR truncated to int
+	x = x + y
+	x = x - y
+	x = x * y
+	x = x / y
+	x = x % y
+	x = x << y
+	x = x >> y
+
+	z = z + 1
+	z = z + 1.0
+	z = z + 1.1 // ERROR truncated to int
+	z = z /* ERROR mismatched types */ + y
+	z = z /* ERROR mismatched types */ - y
+	z = z /* ERROR mismatched types */ * y
+	z = z /* ERROR mismatched types */ / y
+	z = z /* ERROR mismatched types */ % y
+	z = z << y
+	z = z >> y
+}
+
+type myuint uint
+
+func _(x, y uint, z myuint) {
+	x = x + 1
+	x = x + - /* ERROR overflows uint */ 1
+	x = x + 1.0
+	x = x + 1.1 // ERROR truncated to uint
+	x = x + y
+	x = x - y
+	x = x * y
+	x = x / y
+	x = x % y
+	x = x << y
+	x = x >> y
+
+	z = z + 1
+	z = x + - /* ERROR overflows uint */ 1
+	z = z + 1.0
+	z = z + 1.1 // ERROR truncated to uint
+	z = z /* ERROR mismatched types */ + y
+	z = z /* ERROR mismatched types */ - y
+	z = z /* ERROR mismatched types */ * y
+	z = z /* ERROR mismatched types */ / y
+	z = z /* ERROR mismatched types */ % y
+	z = z << y
+	z = z >> y
+}
+
+type myfloat64 float64
+
+func _(x, y float64, z myfloat64) {
+	x = x + 1
+	x = x + -1
+	x = x + 1.0
+	x = x + 1.1
+	x = x + y
+	x = x - y
+	x = x * y
+	x = x / y
+	x = x /* ERROR not defined */ % y
+	x = x /* ERROR operand x .* must be integer */ << y
+	x = x /* ERROR operand x .* must be integer */ >> y
+
+	z = z + 1
+	z = z + -1
+	z = z + 1.0
+	z = z + 1.1
+	z = z /* ERROR mismatched types */ + y
+	z = z /* ERROR mismatched types */ - y
+	z = z /* ERROR mismatched types */ * y
+	z = z /* ERROR mismatched types */ / y
+	z = z /* ERROR mismatched types */ % y
+	z = z /* ERROR operand z .* must be integer */ << y
+	z = z /* ERROR operand z .* must be integer */ >> y
+}
+
+type mystring string
+
+func _(x, y string, z mystring) {
+	x = x + "foo"
+	x = x /* ERROR not defined */ - "foo"
+	x = x /* ERROR mismatched types string and untyped int */ + 1
+	x = x + y
+	x = x /* ERROR not defined */ - y
+	x = x /* ERROR mismatched types string and untyped int */* 10
+}
+
+func f() (a, b int) { return }
+
+func _(x int) {
+	_ = f /* ERROR multiple-value f */ () + 1
+	_ = x + f /* ERROR multiple-value f */ ()
+	_ = f /* ERROR multiple-value f */ () + f
+	_ = f /* ERROR multiple-value f */ () + f /* ERROR multiple-value f */ ()
+}
diff --git a/src/internal/types/testdata/check/expr2.go b/src/internal/types/testdata/check/expr2.go
new file mode 100644
index 0000000..1929664
--- /dev/null
+++ b/src/internal/types/testdata/check/expr2.go
@@ -0,0 +1,260 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// comparisons
+
+package expr2
+
+func _bool() {
+	const t = true == true
+	const f = true == false
+	_ = t /* ERROR operator .* not defined */ < f
+	_ = 0 == t /* ERROR mismatched types untyped int and untyped bool */
+	var b bool
+	var x, y float32
+	b = x < y
+	_ = b
+	_ = struct{b bool}{x < y}
+}
+
+// corner cases
+var (
+	v0 = nil == nil // ERROR operator == not defined on untyped nil
+)
+
+func arrays() {
+	// basics
+	var a, b [10]int
+	_ = a == b
+	_ = a != b
+	_ = a /* ERROR < not defined */ < b
+	_ = a == nil /* ERROR mismatched types */
+
+	type C [10]int
+	var c C
+	_ = a == c
+
+	type D [10]int
+	var d D
+	_ = c == d /* ERROR mismatched types */
+
+	var e [10]func() int
+	_ = e /* ERROR \[10\]func\(\) int cannot be compared */ == e
+}
+
+func structs() {
+	// basics
+	var s, t struct {
+		x int
+		a [10]float32
+		_ bool
+	}
+	_ = s == t
+	_ = s != t
+	_ = s /* ERROR < not defined */ < t
+	_ = s == nil /* ERROR mismatched types */
+
+	type S struct {
+		x int
+		a [10]float32
+		_ bool
+	}
+	type T struct {
+		x int
+		a [10]float32
+		_ bool
+	}
+	var ss S
+	var tt T
+	_ = s == ss
+	_ = ss == tt /* ERROR mismatched types */
+
+	var u struct {
+		x int
+		a [10]map[string]int
+	}
+	_ = u /* ERROR cannot be compared */ == u
+}
+
+func pointers() {
+	// nil
+	_ = nil == nil // ERROR operator == not defined on untyped nil
+	_ = nil != nil // ERROR operator != not defined on untyped nil
+	_ = nil /* ERROR < not defined */ < nil
+	_ = nil /* ERROR <= not defined */ <= nil
+	_ = nil /* ERROR > not defined */ > nil
+	_ = nil /* ERROR >= not defined */ >= nil
+
+	// basics
+	var p, q *int
+	_ = p == q
+	_ = p != q
+
+	_ = p == nil
+	_ = p != nil
+	_ = nil == q
+	_ = nil != q
+
+	_ = p /* ERROR < not defined */ < q
+	_ = p /* ERROR <= not defined */ <= q
+	_ = p /* ERROR > not defined */ > q
+	_ = p /* ERROR >= not defined */ >= q
+
+	// various element types
+	type (
+		S1 struct{}
+		S2 struct{}
+		P1 *S1
+		P2 *S2
+	)
+	var (
+		ps1 *S1
+		ps2 *S2
+		p1 P1
+		p2 P2
+	)
+	_ = ps1 == ps1
+	_ = ps1 == ps2 /* ERROR mismatched types */
+	_ = ps2 == ps1 /* ERROR mismatched types */
+
+	_ = p1 == p1
+	_ = p1 == p2 /* ERROR mismatched types */
+
+	_ = p1 == ps1
+}
+
+func channels() {
+	// basics
+	var c, d chan int
+	_ = c == d
+	_ = c != d
+	_ = c == nil
+	_ = c /* ERROR < not defined */ < d
+
+	// various element types (named types)
+	type (
+		C1 chan int
+		C1r <-chan int
+		C1s chan<- int
+		C2 chan float32
+	)
+	var (
+		c1 C1
+		c1r C1r
+		c1s C1s
+		c1a chan int
+		c2 C2
+	)
+	_ = c1 == c1
+	_ = c1 == c1r /* ERROR mismatched types */
+	_ = c1 == c1s /* ERROR mismatched types */
+	_ = c1r == c1s /* ERROR mismatched types */
+	_ = c1 == c1a
+	_ = c1a == c1
+	_ = c1 == c2 /* ERROR mismatched types */
+	_ = c1a == c2 /* ERROR mismatched types */
+
+	// various element types (unnamed types)
+	var (
+		d1 chan int
+		d1r <-chan int
+		d1s chan<- int
+		d1a chan<- int
+		d2 chan float32
+	)
+	_ = d1 == d1
+	_ = d1 == d1r
+	_ = d1 == d1s
+	_ = d1r == d1s /* ERROR mismatched types */
+	_ = d1 == d1a
+	_ = d1a == d1
+	_ = d1 == d2 /* ERROR mismatched types */
+	_ = d1a == d2 /* ERROR mismatched types */
+}
+
+// for interfaces test
+type S1 struct{}
+type S11 struct{}
+type S2 struct{}
+func (*S1) m() int
+func (*S11) m() int
+func (*S11) n()
+func (*S2) m() float32
+
+func interfaces() {
+	// basics
+	var i, j interface{ m() int }
+	_ = i == j
+	_ = i != j
+	_ = i == nil
+	_ = i /* ERROR < not defined */ < j
+
+	// various interfaces
+	var ii interface { m() int; n() }
+	var k interface { m() float32 }
+	_ = i == ii
+	_ = i == k /* ERROR mismatched types */
+
+	// interfaces vs values
+	var s1 S1
+	var s11 S11
+	var s2 S2
+
+	_ = i == 0 /* ERROR cannot convert */
+	_ = i == s1 /* ERROR mismatched types */
+	_ = i == &s1
+	_ = i == &s11
+
+	_ = i == s2 /* ERROR mismatched types */
+	_ = i == & /* ERROR mismatched types */ s2
+
+	// issue #28164
+	// testcase from issue
+	_ = interface{}(nil) == [ /* ERROR slice can only be compared to nil */ ]int(nil)
+
+	// related cases
+	var e interface{}
+	var s []int
+	var x int
+	_ = e == s // ERROR slice can only be compared to nil
+	_ = s /* ERROR slice can only be compared to nil */ == e
+	_ = e /* ERROR operator < not defined on interface */ < x
+	_ = x < e // ERROR operator < not defined on interface
+}
+
+func slices() {
+	// basics
+	var s []int
+	_ = s == nil
+	_ = s != nil
+	_ = s /* ERROR < not defined */ < nil
+
+	// slices are not otherwise comparable
+	_ = s /* ERROR slice can only be compared to nil */ == s
+	_ = s /* ERROR < not defined */ < s
+}
+
+func maps() {
+	// basics
+	var m map[string]int
+	_ = m == nil
+	_ = m != nil
+	_ = m /* ERROR < not defined */ < nil
+
+	// maps are not otherwise comparable
+	_ = m /* ERROR map can only be compared to nil */ == m
+	_ = m /* ERROR < not defined */ < m
+}
+
+func funcs() {
+	// basics
+	var f func(int) float32
+	_ = f == nil
+	_ = f != nil
+	_ = f /* ERROR < not defined */ < nil
+
+	// funcs are not otherwise comparable
+	_ = f /* ERROR func can only be compared to nil */ == f
+	_ = f /* ERROR < not defined */ < f
+}
diff --git a/src/internal/types/testdata/check/expr3.go b/src/internal/types/testdata/check/expr3.go
new file mode 100644
index 0000000..2da5984
--- /dev/null
+++ b/src/internal/types/testdata/check/expr3.go
@@ -0,0 +1,564 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package expr3
+
+import "time"
+
+func indexes() {
+	_ = 1 /* ERROR "cannot index" */ [0]
+	_ = indexes /* ERROR "cannot index" */ [0]
+	_ = ( /* ERROR "cannot slice" */ 12 + 3)[1:2]
+
+	var a [10]int
+	_ = a[true /* ERROR "cannot convert" */ ]
+	_ = a["foo" /* ERROR "cannot convert" */ ]
+	_ = a[1.1 /* ERROR "truncated" */ ]
+	_ = a[1.0]
+	_ = a[- /* ERROR "negative" */ 1]
+	_ = a[- /* ERROR "negative" */ 1 :]
+	_ = a[: - /* ERROR "negative" */ 1]
+	_ = a[: /* ERROR "middle index required" */ : /* ERROR "final index required" */ ]
+	_ = a[0: /* ERROR "middle index required" */ : /* ERROR "final index required" */ ]
+	_ = a[0: /* ERROR "middle index required" */ :10]
+	_ = a[:10:10]
+
+	var a0 int
+	a0 = a[0]
+	_ = a0
+	var a1 int32
+	a1 = a /* ERROR "cannot use .* in assignment" */ [1]
+	_ = a1
+
+	_ = a[9]
+	_ = a[10 /* ERROR "index .* out of bounds" */ ]
+	_ = a[1 /* ERROR "overflows" */ <<100]
+	_ = a[1<< /* ERROR "constant shift overflow" */ 1000] // no out-of-bounds follow-on error
+	_ = a[10:]
+	_ = a[:10]
+	_ = a[10:10]
+	_ = a[11 /* ERROR "index .* out of bounds" */ :]
+	_ = a[: 11 /* ERROR "index .* out of bounds" */ ]
+	_ = a[: 1 /* ERROR "overflows" */ <<100]
+	_ = a[:10:10]
+	_ = a[:11 /* ERROR "index .* out of bounds" */ :10]
+	_ = a[:10:11 /* ERROR "index .* out of bounds" */ ]
+	_ = a[10:0 /* ERROR "invalid slice indices" */ :10]
+	_ = a[0:10:0 /* ERROR "invalid slice indices" */ ]
+	_ = a[10:0 /* ERROR "invalid slice indices" */:0]
+	_ = &a /* ERROR "cannot take address" */ [:10]
+
+	pa := &a
+	_ = pa[9]
+	_ = pa[10 /* ERROR "index .* out of bounds" */ ]
+	_ = pa[1 /* ERROR "overflows" */ <<100]
+	_ = pa[10:]
+	_ = pa[:10]
+	_ = pa[10:10]
+	_ = pa[11 /* ERROR "index .* out of bounds" */ :]
+	_ = pa[: 11 /* ERROR "index .* out of bounds" */ ]
+	_ = pa[: 1 /* ERROR "overflows" */ <<100]
+	_ = pa[:10:10]
+	_ = pa[:11 /* ERROR "index .* out of bounds" */ :10]
+	_ = pa[:10:11 /* ERROR "index .* out of bounds" */ ]
+	_ = pa[10:0 /* ERROR "invalid slice indices" */ :10]
+	_ = pa[0:10:0 /* ERROR "invalid slice indices" */ ]
+	_ = pa[10:0 /* ERROR "invalid slice indices" */ :0]
+	_ = &pa /* ERROR "cannot take address" */ [:10]
+
+	var b [0]int
+	_ = b[0 /* ERROR "index .* out of bounds" */ ]
+	_ = b[:]
+	_ = b[0:]
+	_ = b[:0]
+	_ = b[0:0]
+	_ = b[0:0:0]
+	_ = b[1 /* ERROR "index .* out of bounds" */ :0:0]
+
+	var s []int
+	_ = s[- /* ERROR "negative" */ 1]
+	_ = s[- /* ERROR "negative" */ 1 :]
+	_ = s[: - /* ERROR "negative" */ 1]
+	_ = s[0]
+	_ = s[1:2]
+	_ = s[2:1 /* ERROR "invalid slice indices" */ ]
+	_ = s[2:]
+	_ = s[: 1 /* ERROR "overflows" */ <<100]
+	_ = s[1 /* ERROR "overflows" */ <<100 :]
+	_ = s[1 /* ERROR "overflows" */ <<100 : 1 /* ERROR "overflows" */ <<100]
+	_ = s[: /* ERROR "middle index required" */ :  /* ERROR "final index required" */ ]
+	_ = s[:10:10]
+	_ = s[10:0 /* ERROR "invalid slice indices" */ :10]
+	_ = s[0:10:0 /* ERROR "invalid slice indices" */ ]
+	_ = s[10:0 /* ERROR "invalid slice indices" */ :0]
+	_ = &s /* ERROR "cannot take address" */ [:10]
+
+	var m map[string]int
+	_ = m[0 /* ERROR "cannot use .* in map index" */ ]
+	_ = m /* ERROR "cannot slice" */ ["foo" : "bar"]
+	_ = m["foo"]
+	// ok is of type bool
+	type mybool bool
+	var ok mybool
+	_, ok = m["bar"]
+	_ = ok
+	_ = m/* ERROR "mismatched types int and untyped string" */[0 /* ERROR "cannot use 0" */ ] + "foo"
+
+	var t string
+	_ = t[- /* ERROR "negative" */ 1]
+	_ = t[- /* ERROR "negative" */ 1 :]
+	_ = t[: - /* ERROR "negative" */ 1]
+	_ = t[1:2:3 /* ERROR "3-index slice of string" */ ]
+	_ = "foo"[1:2:3 /* ERROR "3-index slice of string" */ ]
+	var t0 byte
+	t0 = t[0]
+	_ = t0
+	var t1 rune
+	t1 = t /* ERROR "cannot use .* in assignment" */ [2]
+	_ = t1
+	_ = ("foo" + "bar")[5]
+	_ = ("foo" + "bar")[6 /* ERROR "index .* out of bounds" */ ]
+
+	const c = "foo"
+	_ = c[- /* ERROR "negative" */ 1]
+	_ = c[- /* ERROR "negative" */ 1 :]
+	_ = c[: - /* ERROR "negative" */ 1]
+	var c0 byte
+	c0 = c[0]
+	_ = c0
+	var c2 float32
+	c2 = c /* ERROR "cannot use .* in assignment" */ [2]
+	_ = c[3 /* ERROR "index .* out of bounds" */ ]
+	_ = ""[0 /* ERROR "index .* out of bounds" */ ]
+	_ = c2
+
+	_ = s[1<<30] // no compile-time error here
+
+	// issue 4913
+	type mystring string
+	var ss string
+	var ms mystring
+	var i, j int
+	ss = "foo"[1:2]
+	ss = "foo"[i:j]
+	ms = "foo" /* ERROR "cannot use .* in assignment" */ [1:2]
+	ms = "foo" /* ERROR "cannot use .* in assignment" */ [i:j]
+	_, _ = ss, ms
+}
+
+type T struct {
+	x int
+	y func()
+}
+
+func (*T) m() {}
+
+func method_expressions() {
+	_ = T.a /* ERROR "no field or method" */
+	_ = T.x /* ERROR "has no method" */
+	_ = T.m /* ERROR "invalid method expression T\.m \(needs pointer receiver \(\*T\)\.m\)" */
+	_ = (*T).m
+
+	var f func(*T) = T.m /* ERROR "invalid method expression T\.m \(needs pointer receiver \(\*T\)\.m\)" */
+	var g func(*T) = (*T).m
+	_, _ = f, g
+
+	_ = T.y /* ERROR "has no method" */
+	_ = (*T).y /* ERROR "has no method" */
+}
+
+func struct_literals() {
+	type T0 struct {
+		a, b, c int
+	}
+
+	type T1 struct {
+		T0
+		a, b int
+		u float64
+		s string
+	}
+
+	// keyed elements
+	_ = T1{}
+	_ = T1{a: 0, 1 /* ERROR "mixture of .* elements" */ }
+	_ = T1{aa /* ERROR "unknown field" */ : 0}
+	_ = T1{1 /* ERROR "invalid field name" */ : 0}
+	_ = T1{a: 0, s: "foo", u: 0, a /* ERROR "duplicate field" */: 10}
+	_ = T1{a: "foo" /* ERROR "cannot use .* in struct literal" */ }
+	_ = T1{c /* ERROR "unknown field" */ : 0}
+	_ = T1{T0: { /* ERROR "missing type" */ }} // struct literal element type may not be elided
+	_ = T1{T0: T0{}}
+	_ = T1{T0 /* ERROR "invalid field name" */ .a: 0}
+
+	// unkeyed elements
+	_ = T0{1, 2, 3}
+	_ = T0{1, b /* ERROR "mixture" */ : 2, 3}
+	_ = T0{1, 2} /* ERROR "too few values" */
+	_ = T0{1, 2, 3, 4  /* ERROR "too many values" */ }
+	_ = T0{1, "foo" /* ERROR "cannot use .* in struct literal" */, 3.4  /* ERROR "cannot use .*\(truncated\)" */}
+
+	// invalid type
+	type P *struct{
+		x int
+	}
+	_ = P /* ERROR "invalid composite literal type" */ {}
+
+	// unexported fields
+	_ = time.Time{}
+	_ = time.Time{sec /* ERROR "unknown field" */ : 0}
+	_ = time.Time{
+		0 /* ERROR implicit assignment to unexported field wall in struct literal */,
+		0 /* ERROR implicit assignment */ ,
+		nil /* ERROR implicit assignment */ ,
+	}
+}
+
+func array_literals() {
+	type A0 [0]int
+	_ = A0{}
+	_ = A0{0 /* ERROR "index .* out of bounds" */}
+	_ = A0{0 /* ERROR "index .* out of bounds" */ : 0}
+
+	type A1 [10]int
+	_ = A1{}
+	_ = A1{0, 1, 2}
+	_ = A1{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
+	_ = A1{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 /* ERROR "index .* out of bounds" */ }
+	_ = A1{- /* ERROR "negative" */ 1: 0}
+	_ = A1{8: 8, 9}
+	_ = A1{8: 8, 9, 10 /* ERROR "index .* out of bounds" */ }
+	_ = A1{0, 1, 2, 0 /* ERROR "duplicate index" */ : 0, 3: 3, 4}
+	_ = A1{5: 5, 6, 7, 3: 3, 4}
+	_ = A1{5: 5, 6, 7, 3: 3, 4, 5 /* ERROR "duplicate index" */ }
+	_ = A1{10 /* ERROR "index .* out of bounds" */ : 10, 10 /* ERROR "index .* out of bounds" */ : 10}
+	_ = A1{5: 5, 6, 7, 3: 3, 1 /* ERROR "overflows" */ <<100: 4, 5 /* ERROR "duplicate index" */ }
+	_ = A1{5: 5, 6, 7, 4: 4, 1 /* ERROR "overflows" */ <<100: 4}
+	_ = A1{2.0}
+	_ = A1{2.1 /* ERROR "truncated" */ }
+	_ = A1{"foo" /* ERROR "cannot use .* in array or slice literal" */ }
+
+	// indices must be integer constants
+	i := 1
+	const f = 2.1
+	const s = "foo"
+	_ = A1{i /* ERROR "index i must be integer constant" */ : 0}
+	_ = A1{f /* ERROR "truncated" */ : 0}
+	_ = A1{s /* ERROR "cannot convert" */ : 0}
+
+	a0 := [...]int{}
+	assert(len(a0) == 0)
+
+	a1 := [...]int{0, 1, 2}
+	assert(len(a1) == 3)
+	var a13 [3]int
+	var a14 [4]int
+	a13 = a1
+	a14 = a1 /* ERROR "cannot use .* in assignment" */
+	_, _ = a13, a14
+
+	a2 := [...]int{- /* ERROR "negative" */ 1: 0}
+	_ = a2
+
+	a3 := [...]int{0, 1, 2, 0 /* ERROR "duplicate index" */ : 0, 3: 3, 4}
+	assert(len(a3) == 5) // somewhat arbitrary
+
+	a4 := [...]complex128{0, 1, 2, 1<<10-2: -1i, 1i, 400: 10, 12, 14}
+	assert(len(a4) == 1024)
+
+	// composite literal element types may be elided
+	type T []int
+	_ = [10]T{T{}, {}, 5: T{1, 2, 3}, 7: {1, 2, 3}}
+	a6 := [...]T{T{}, {}, 5: T{1, 2, 3}, 7: {1, 2, 3}}
+	assert(len(a6) == 8)
+
+	// recursively so
+	_ = [10][10]T{{}, [10]T{{}}, {{1, 2, 3}}}
+
+	// from the spec
+	type Point struct { x, y float32 }
+	_ = [...]Point{Point{1.5, -3.5}, Point{0, 0}}
+	_ = [...]Point{{1.5, -3.5}, {0, 0}}
+	_ = [][]int{[]int{1, 2, 3}, []int{4, 5}}
+	_ = [][]int{{1, 2, 3}, {4, 5}}
+	_ = [...]*Point{&Point{1.5, -3.5}, &Point{0, 0}}
+	_ = [...]*Point{{1.5, -3.5}, {0, 0}}
+}
+
+func slice_literals() {
+	type S0 []int
+	_ = S0{}
+	_ = S0{0, 1, 2}
+	_ = S0{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
+	_ = S0{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
+	_ = S0{- /* ERROR "negative" */ 1: 0}
+	_ = S0{8: 8, 9}
+	_ = S0{8: 8, 9, 10}
+	_ = S0{0, 1, 2, 0 /* ERROR "duplicate index" */ : 0, 3: 3, 4}
+	_ = S0{5: 5, 6, 7, 3: 3, 4}
+	_ = S0{5: 5, 6, 7, 3: 3, 4, 5 /* ERROR "duplicate index" */ }
+	_ = S0{10: 10, 10 /* ERROR "duplicate index" */ : 10}
+	_ = S0{5: 5, 6, 7, 3: 3, 1 /* ERROR "overflows" */ <<100: 4, 5 /* ERROR "duplicate index" */ }
+	_ = S0{5: 5, 6, 7, 4: 4, 1 /* ERROR "overflows" */ <<100: 4}
+	_ = S0{2.0}
+	_ = S0{2.1 /* ERROR "truncated" */ }
+	_ = S0{"foo" /* ERROR "cannot use .* in array or slice literal" */ }
+
+	// indices must be resolved correctly
+	const index1 = 1
+	_ = S0{index1: 1}
+	_ = S0{index2: 2}
+	_ = S0{index3 /* ERROR "undefined" */ : 3}
+
+	// indices must be integer constants
+	i := 1
+	const f = 2.1
+	const s = "foo"
+	_ = S0{i /* ERROR "index i must be integer constant" */ : 0}
+	_ = S0{f /* ERROR "truncated" */ : 0}
+	_ = S0{s /* ERROR "cannot convert" */ : 0}
+
+	// composite literal element types may be elided
+	type T []int
+	_ = []T{T{}, {}, 5: T{1, 2, 3}, 7: {1, 2, 3}}
+	_ = [][]int{{1, 2, 3}, {4, 5}}
+
+	// recursively so
+	_ = [][]T{{}, []T{{}}, {{1, 2, 3}}}
+
+	// issue 17954
+	type T0 *struct { s string }
+	_ = []T0{{}}
+	_ = []T0{{"foo"}}
+
+	type T1 *struct{ int }
+	_ = []T1{}
+	_ = []T1{{0}, {1}, {2}}
+
+	type T2 T1
+	_ = []T2{}
+	_ = []T2{{0}, {1}, {2}}
+
+	_ = map[T0]T2{}
+	_ = map[T0]T2{{}: {}}
+}
+
+const index2 int = 2
+
+type N int
+func (N) f() {}
+
+func map_literals() {
+	type M0 map[string]int
+	type M1 map[bool]int
+	type M2 map[*int]int
+
+	_ = M0{}
+	_ = M0{1 /* ERROR "missing key" */ }
+	_ = M0{1 /* ERROR "cannot use .* in map literal" */ : 2}
+	_ = M0{"foo": "bar" /* ERROR "cannot use .* in map literal" */ }
+	_ = M0{"foo": 1, "bar": 2, "foo" /* ERROR "duplicate key" */ : 3 }
+
+	_ = map[interface{}]int{2: 1, 2 /* ERROR "duplicate key" */ : 1}
+	_ = map[interface{}]int{int(2): 1, int16(2): 1}
+	_ = map[interface{}]int{int16(2): 1, int16 /* ERROR "duplicate key" */ (2): 1}
+
+	type S string
+
+	_ = map[interface{}]int{"a": 1, "a" /* ERROR "duplicate key" */ : 1}
+	_ = map[interface{}]int{"a": 1, S("a"): 1}
+	_ = map[interface{}]int{S("a"): 1, S /* ERROR "duplicate key" */ ("a"): 1}
+	_ = map[interface{}]int{1.0: 1, 1.0 /* ERROR "duplicate key" */: 1}
+	_ = map[interface{}]int{int64(-1): 1, int64 /* ERROR "duplicate key" */ (-1) : 1}
+	_ = map[interface{}]int{^uint64(0): 1, ^ /* ERROR "duplicate key" */ uint64(0): 1}
+	_ = map[interface{}]int{complex(1,2): 1, complex /* ERROR "duplicate key" */ (1,2) : 1}
+
+	type I interface {
+		f()
+	}
+
+	_ = map[I]int{N(0): 1, N(2): 1}
+	_ = map[I]int{N(2): 1, N /* ERROR "duplicate key" */ (2): 1}
+
+	// map keys must be resolved correctly
+	key1 := "foo"
+	_ = M0{key1: 1}
+	_ = M0{key2: 2}
+	_ = M0{key3 /* ERROR "undefined" */ : 2}
+
+	var value int
+	_ = M1{true: 1, false: 0}
+	_ = M2{nil: 0, &value: 1}
+
+	// composite literal element types may be elided
+	type T [2]int
+	_ = map[int]T{0: T{3, 4}, 1: {5, 6}}
+
+	// recursively so
+	_ = map[int][]T{0: {}, 1: {{}, T{1, 2}}}
+
+	// composite literal key types may be elided
+	_ = map[T]int{T{3, 4}: 0, {5, 6}: 1}
+
+	// recursively so
+	_ = map[[2]T]int{{}: 0, {{}}: 1, [2]T{{}}: 2, {T{1, 2}}: 3}
+
+	// composite literal element and key types may be elided
+	_ = map[T]T{{}: {}, {1, 2}: T{3, 4}, T{4, 5}: {}}
+	_ = map[T]M0{{} : {}, T{1, 2}: M0{"foo": 0}, {1, 3}: {"foo": 1}}
+
+	// recursively so
+	_ = map[[2]T][]T{{}: {}, {{}}: {{}, T{1, 2}}, [2]T{{}}: nil, {T{1, 2}}: {{}, {}}}
+
+	// from the spec
+	type Point struct { x, y float32 }
+	_ = map[string]Point{"orig": {0, 0}}
+	_ = map[*Point]string{{0, 0}: "orig"}
+
+	// issue 17954
+	type T0 *struct{ s string }
+	type T1 *struct{ int }
+	type T2 T1
+
+	_ = map[T0]T2{}
+	_ = map[T0]T2{{}: {}}
+}
+
+var key2 string = "bar"
+
+type I interface {
+	m()
+}
+
+type I2 interface {
+	m(int)
+}
+
+type T1 struct{}
+type T2 struct{}
+
+func (T2) m(int) {}
+
+type mybool bool
+
+func type_asserts() {
+	var x int
+	_ = x /* ERROR "not an interface" */ .(int)
+
+	var e interface{}
+	var ok bool
+	x, ok = e.(int)
+	_ = ok
+
+	// ok value is of type bool
+	var myok mybool
+	_, myok = e.(int)
+	_ = myok
+
+	var t I
+	_ = t /* ERROR "use of .* outside type switch" */ .(type)
+	_ = t /* ERROR "m has pointer receiver" */ .(T)
+	_ = t.(*T)
+	_ = t /* ERROR "missing method m" */ .(T1)
+	_ = t /* ERROR "wrong type for method m" */ .(T2)
+	_ = t /* STRICT "wrong type for method m" */ .(I2) // only an error in strict mode (issue 8561)
+
+	// e doesn't statically have an m, but may have one dynamically.
+	_ = e.(I2)
+}
+
+func f0() {}
+func f1(x int) {}
+func f2(u float32, s string) {}
+func fs(s []byte) {}
+func fv(x ...int) {}
+func fi(x ... interface{}) {}
+func (T) fm(x ...int)
+
+func g0() {}
+func g1() int { return 0}
+func g2() (u float32, s string) { return }
+func gs() []byte { return nil }
+
+func _calls() {
+	var x int
+	var y float32
+	var s []int
+
+	f0()
+	_ = f0 /* ERROR "used as value" */ ()
+	f0(g0 /* ERROR "too many arguments" */ )
+
+	f1(0)
+	f1(x)
+	f1(10.0)
+	f1() /* ERROR "not enough arguments in call to f1\n\thave \(\)\n\twant \(int\)" */
+	f1(x, y /* ERROR "too many arguments in call to f1\n\thave \(int, float32\)\n\twant \(int\)" */ )
+	f1(s /* ERROR "cannot use .* in argument" */ )
+	f1(x ... /* ERROR "cannot use ..." */ )
+	f1(g0 /* ERROR "used as value" */ ())
+	f1(g1())
+	f1(g2 /* ERROR "too many arguments in call to f1\n\thave \(float32, string\)\n\twant \(int\)" */ ())
+
+	f2() /* ERROR "not enough arguments in call to f2\n\thave \(\)\n\twant \(float32, string\)" */
+	f2(3.14) /* ERROR "not enough arguments in call to f2\n\thave \(number\)\n\twant \(float32, string\)" */
+	f2(3.14, "foo")
+	f2(x /* ERROR "cannot use .* in argument" */ , "foo")
+	f2(g0 /* ERROR "used as value" */ ())
+	f2(g1()) /* ERROR "not enough arguments in call to f2\n\thave \(int\)\n\twant \(float32, string\)" */
+	f2(g2())
+
+	fs() /* ERROR "not enough arguments" */
+	fs(g0 /* ERROR "used as value" */ ())
+	fs(g1 /* ERROR "cannot use .* in argument" */ ())
+	fs(g2 /* ERROR "too many arguments" */ ())
+	fs(gs())
+
+	fv()
+	fv(1, 2.0, x)
+	fv(s /* ERROR "cannot use .* in argument" */ )
+	fv(s...)
+	fv(x /* ERROR "cannot use" */ ...)
+	fv(1, s /* ERROR "too many arguments" */ ...)
+	fv(gs /* ERROR "cannot use .* in argument" */ ())
+	fv(gs /* ERROR "cannot use .* in argument" */ ()...)
+
+	var t T
+	t.fm()
+	t.fm(1, 2.0, x)
+	t.fm(s /* ERROR "cannot use .* in argument" */ )
+	t.fm(g1())
+	t.fm(1, s /* ERROR "too many arguments" */ ...)
+	t.fm(gs /* ERROR "cannot use .* in argument" */ ())
+	t.fm(gs /* ERROR "cannot use .* in argument" */ ()...)
+
+	T.fm(t, )
+	T.fm(t, 1, 2.0, x)
+	T.fm(t, s /* ERROR "cannot use .* in argument" */ )
+	T.fm(t, g1())
+	T.fm(t, 1, s /* ERROR "too many arguments" */ ...)
+	T.fm(t, gs /* ERROR "cannot use .* in argument" */ ())
+	T.fm(t, gs /* ERROR "cannot use .* in argument" */ ()...)
+
+	var i interface{ fm(x ...int) } = t
+	i.fm()
+	i.fm(1, 2.0, x)
+	i.fm(s /* ERROR "cannot use .* in argument" */ )
+	i.fm(g1())
+	i.fm(1, s /* ERROR "too many arguments" */ ...)
+	i.fm(gs /* ERROR "cannot use .* in argument" */ ())
+	i.fm(gs /* ERROR "cannot use .* in argument" */ ()...)
+
+	fi()
+	fi(1, 2.0, x, 3.14, "foo")
+	fi(g2())
+	fi(0, g2)
+	fi(0, g2 /* ERROR "multiple-value g2" */ ())
+}
+
+func issue6344() {
+	type T []interface{}
+	var x T
+	fi(x...) // ... applies also to named slices
+}
diff --git a/src/internal/types/testdata/check/funcinference.go b/src/internal/types/testdata/check/funcinference.go
new file mode 100644
index 0000000..fedf199
--- /dev/null
+++ b/src/internal/types/testdata/check/funcinference.go
@@ -0,0 +1,104 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package funcInference
+
+import "strconv"
+
+type any interface{}
+
+func f0[A any, B interface{*C}, C interface{*D}, D interface{*A}](A, B, C, D) {}
+func _() {
+	f := f0[string]
+	f("a", nil, nil, nil)
+	f0("a", nil, nil, nil)
+}
+
+func f1[A any, B interface{*A}](A, B) {}
+func _() {
+	f := f1[int]
+	f(int(0), new(int))
+	f1(int(0), new(int))
+}
+
+func f2[A any, B interface{[]A}](A, B) {}
+func _() {
+	f := f2[byte]
+	f(byte(0), []byte{})
+	f2(byte(0), []byte{})
+}
+
+// Embedding stand-alone type parameters is not permitted for now. Disabled.
+// func f3[A any, B interface{~C}, C interface{~*A}](A, B, C)
+// func _() {
+// 	f := f3[int]
+// 	var x int
+// 	f(x, &x, &x)
+// 	f3(x, &x, &x)
+// }
+
+func f4[A any, B interface{[]C}, C interface{*A}](A, B, C) {}
+func _() {
+	f := f4[int]
+	var x int
+	f(x, []*int{}, &x)
+	f4(x, []*int{}, &x)
+}
+
+func f5[A interface{struct{b B; c C}}, B any, C interface{*B}](x B) A { panic(0) }
+func _() {
+	x := f5(1.2)
+	var _ float64 = x.b
+	var _ float64 = *x.c
+}
+
+func f6[A any, B interface{~struct{f []A}}](B) A { panic(0) }
+func _() {
+	x := f6(struct{f []string}{})
+	var _ string = x
+}
+
+func f7[A interface{*B}, B interface{~*A}]() {}
+
+// More realistic examples
+
+func Double[S interface{ ~[]E }, E interface{ ~int | ~int8 | ~int16 | ~int32 | ~int64 }](s S) S {
+	r := make(S, len(s))
+	for i, v := range s {
+		r[i] = v + v
+	}
+	return r
+}
+
+type MySlice []int
+
+var _ = Double(MySlice{1})
+
+// From the draft design.
+
+type Setter[B any] interface {
+	Set(string)
+	*B
+}
+
+func FromStrings[T interface{}, PT Setter[T]](s []string) []T {
+	result := make([]T, len(s))
+	for i, v := range s {
+		// The type of &result[i] is *T which is in the type set
+		// of Setter, so we can convert it to PT.
+		p := PT(&result[i])
+		// PT has a Set method.
+		p.Set(v)
+	}
+	return result
+}
+
+type Settable int
+
+func (p *Settable) Set(s string) {
+	i, _ := strconv.Atoi(s) // real code should not ignore the error
+	*p = Settable(i)
+}
+
+var _ = FromStrings[Settable]([]string{"1", "2"})
diff --git a/src/internal/types/testdata/check/go1_12.go b/src/internal/types/testdata/check/go1_12.go
new file mode 100644
index 0000000..56c6d5a
--- /dev/null
+++ b/src/internal/types/testdata/check/go1_12.go
@@ -0,0 +1,36 @@
+// -lang=go1.12
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check Go language version-specific errors.
+
+package p
+
+// numeric literals
+const (
+	_ = 1_000 // ERROR "underscores in numeric literals requires go1.13 or later"
+	_ = 0b111 // ERROR "binary literals requires go1.13 or later"
+	_ = 0o567 // ERROR "0o/0O-style octal literals requires go1.13 or later"
+	_ = 0xabc // ok
+	_ = 0x0p1 // ERROR "hexadecimal floating-point literals requires go1.13 or later"
+
+	_ = 0B111 // ERROR "binary"
+	_ = 0O567 // ERROR "octal"
+	_ = 0Xabc // ok
+	_ = 0X0P1 // ERROR "hexadecimal floating-point"
+
+	_ = 1_000i // ERROR "underscores"
+	_ = 0b111i // ERROR "binary"
+	_ = 0o567i // ERROR "octal"
+	_ = 0xabci // ERROR "hexadecimal floating-point"
+	_ = 0x0p1i // ERROR "hexadecimal floating-point"
+)
+
+// signed shift counts
+var (
+	s int
+	_ = 1 << s // ERROR "invalid operation: signed shift count s \(variable of type int\) requires go1.13 or later"
+	_ = 1 >> s // ERROR "signed shift count"
+)
diff --git a/src/internal/types/testdata/check/go1_13.go b/src/internal/types/testdata/check/go1_13.go
new file mode 100644
index 0000000..cc7861d
--- /dev/null
+++ b/src/internal/types/testdata/check/go1_13.go
@@ -0,0 +1,23 @@
+// -lang=go1.13
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check Go language version-specific errors.
+
+package p
+
+// interface embedding
+
+type I interface { m() }
+
+type _ interface {
+	m()
+	I // ERROR "duplicate method m"
+}
+
+type _ interface {
+	I
+	I // ERROR "duplicate method m"
+}
diff --git a/src/internal/types/testdata/check/go1_16.go b/src/internal/types/testdata/check/go1_16.go
new file mode 100644
index 0000000..81b5290
--- /dev/null
+++ b/src/internal/types/testdata/check/go1_16.go
@@ -0,0 +1,15 @@
+// -lang=go1.16
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check Go language version-specific errors.
+
+package p
+
+type Slice []byte
+type Array [8]byte
+
+var s Slice
+var p = (*Array)(s /* ERROR requires go1.17 or later */ )
diff --git a/src/internal/types/testdata/check/go1_19.go b/src/internal/types/testdata/check/go1_19.go
new file mode 100644
index 0000000..f899d93
--- /dev/null
+++ b/src/internal/types/testdata/check/go1_19.go
@@ -0,0 +1,15 @@
+// -lang=go1.19
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check Go language version-specific errors.
+
+package p
+
+type Slice []byte
+type Array [8]byte
+
+var s Slice
+var p = (Array)(s /* ERROR requires go1.20 or later */)
diff --git a/src/internal/types/testdata/check/go1_8.go b/src/internal/types/testdata/check/go1_8.go
new file mode 100644
index 0000000..99f2fd4
--- /dev/null
+++ b/src/internal/types/testdata/check/go1_8.go
@@ -0,0 +1,12 @@
+// -lang=go1.8
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check Go language version-specific errors.
+
+package p
+
+// type alias declarations
+type any = /* ERROR type aliases requires go1.9 or later */ interface{}
diff --git a/src/internal/types/testdata/check/gotos.go b/src/internal/types/testdata/check/gotos.go
new file mode 100644
index 0000000..069a94b
--- /dev/null
+++ b/src/internal/types/testdata/check/gotos.go
@@ -0,0 +1,560 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file is a modified copy of $GOROOT/test/goto.go.
+
+package gotos
+
+var (
+	i, n int
+	x    []int
+	c    chan int
+	m    map[int]int
+	s    string
+)
+
+// goto after declaration okay
+func _() {
+	x := 1
+	goto L
+L:
+	_ = x
+}
+
+// goto before declaration okay
+func _() {
+	goto L
+L:
+	x := 1
+	_ = x
+}
+
+// goto across declaration not okay
+func _() {
+	goto L /* ERROR "goto L jumps over variable declaration at line 36" */
+	x := 1
+	_ = x
+L:
+}
+
+// goto across declaration in inner scope okay
+func _() {
+	goto L
+	{
+		x := 1
+		_ = x
+	}
+L:
+}
+
+// goto across declaration after inner scope not okay
+func _() {
+	goto L /* ERROR "goto L jumps over variable declaration at line 58" */
+	{
+		x := 1
+		_ = x
+	}
+	x := 1
+	_ = x
+L:
+}
+
+// goto across declaration in reverse okay
+func _() {
+L:
+	x := 1
+	_ = x
+	goto L
+}
+
+func _() {
+L: L1:
+	x := 1
+	_ = x
+	goto L
+	goto L1
+}
+
+// error shows first offending variable
+func _() {
+	goto L /* ERROR "goto L jumps over variable declaration at line 84" */
+	x := 1
+	_ = x
+	y := 1
+	_ = y
+L:
+}
+
+// goto not okay even if code path is dead
+func _() {
+	goto L /* ERROR "goto L jumps over variable declaration" */
+	x := 1
+	_ = x
+	y := 1
+	_ = y
+	return
+L:
+}
+
+// goto into outer block okay
+func _() {
+	{
+		goto L
+	}
+L:
+}
+
+func _() {
+	{
+		goto L
+		goto L1
+	}
+L: L1:
+}
+
+// goto backward into outer block okay
+func _() {
+L:
+	{
+		goto L
+	}
+}
+
+func _() {
+L: L1:
+	{
+		goto L
+		goto L1
+	}
+}
+
+// goto into inner block not okay
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	{
+	L:
+	}
+}
+
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	goto L1 /* ERROR "goto L1 jumps into block" */
+	{
+	L: L1:
+	}
+}
+
+// goto backward into inner block still not okay
+func _() {
+	{
+	L:
+	}
+	goto L /* ERROR "goto L jumps into block" */
+}
+
+func _() {
+	{
+	L: L1:
+	}
+	goto L /* ERROR "goto L jumps into block" */
+	goto L1 /* ERROR "goto L1 jumps into block" */
+}
+
+// error shows first (outermost) offending block
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	{
+		{
+			{
+			L:
+			}
+		}
+	}
+}
+
+// error prefers block diagnostic over declaration diagnostic
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	x := 1
+	_ = x
+	{
+	L:
+	}
+}
+
+// many kinds of blocks, all invalid to jump into or among,
+// but valid to jump out of
+
+// if
+
+func _() {
+L:
+	if true {
+		goto L
+	}
+}
+
+func _() {
+L:
+	if true {
+		goto L
+	} else {
+	}
+}
+
+func _() {
+L:
+	if false {
+	} else {
+		goto L
+	}
+}
+
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	if true {
+	L:
+	}
+}
+
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	if true {
+	L:
+	} else {
+	}
+}
+
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	if true {
+	} else {
+	L:
+	}
+}
+
+func _() {
+	if false {
+	L:
+	} else {
+		goto L /* ERROR "goto L jumps into block" */
+	}
+}
+
+func _() {
+	if true {
+		goto L /* ERROR "goto L jumps into block" */
+	} else {
+	L:
+	}
+}
+
+func _() {
+	if true {
+		goto L /* ERROR "goto L jumps into block" */
+	} else if false {
+	L:
+	}
+}
+
+func _() {
+	if true {
+		goto L /* ERROR "goto L jumps into block" */
+	} else if false {
+	L:
+	} else {
+	}
+}
+
+func _() {
+	if true {
+		goto L /* ERROR "goto L jumps into block" */
+	} else if false {
+	} else {
+	L:
+	}
+}
+
+func _() {
+	if true {
+		goto L /* ERROR "goto L jumps into block" */
+	} else {
+		L:
+	}
+}
+
+func _() {
+	if true {
+		L:
+	} else {
+		goto L /* ERROR "goto L jumps into block" */
+	}
+}
+
+// for
+
+func _() {
+	for {
+		goto L
+	}
+L:
+}
+
+func _() {
+	for {
+		goto L
+	L:
+	}
+}
+
+func _() {
+	for {
+	L:
+	}
+	goto L /* ERROR "goto L jumps into block" */
+}
+
+func _() {
+	for {
+		goto L
+	L1:
+	}
+L:
+	goto L1 /* ERROR "goto L1 jumps into block" */
+}
+
+func _() {
+	for i < n {
+	L:
+	}
+	goto L /* ERROR "goto L jumps into block" */
+}
+
+func _() {
+	for i = 0; i < n; i++ {
+	L:
+	}
+	goto L /* ERROR "goto L jumps into block" */
+}
+
+func _() {
+	for i = range x {
+	L:
+	}
+	goto L /* ERROR "goto L jumps into block" */
+}
+
+func _() {
+	for i = range c {
+	L:
+	}
+	goto L /* ERROR "goto L jumps into block" */
+}
+
+func _() {
+	for i = range m {
+	L:
+	}
+	goto L /* ERROR "goto L jumps into block" */
+}
+
+func _() {
+	for i = range s {
+	L:
+	}
+	goto L /* ERROR "goto L jumps into block" */
+}
+
+// switch
+
+func _() {
+L:
+	switch i {
+	case 0:
+		goto L
+	}
+}
+
+func _() {
+L:
+	switch i {
+	case 0:
+
+	default:
+		goto L
+	}
+}
+
+func _() {
+	switch i {
+	case 0:
+
+	default:
+	L:
+		goto L
+	}
+}
+
+func _() {
+	switch i {
+	case 0:
+
+	default:
+		goto L
+	L:
+	}
+}
+
+func _() {
+	switch i {
+	case 0:
+		goto L
+	L:
+		;
+	default:
+	}
+}
+
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	switch i {
+	case 0:
+	L:
+	}
+}
+
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	switch i {
+	case 0:
+	L:
+		;
+	default:
+	}
+}
+
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	switch i {
+	case 0:
+	default:
+	L:
+	}
+}
+
+func _() {
+	switch i {
+	default:
+		goto L /* ERROR "goto L jumps into block" */
+	case 0:
+	L:
+	}
+}
+
+func _() {
+	switch i {
+	case 0:
+	L:
+		;
+	default:
+		goto L /* ERROR "goto L jumps into block" */
+	}
+}
+
+// select
+// different from switch.  the statement has no implicit block around it.
+
+func _() {
+L:
+	select {
+	case <-c:
+		goto L
+	}
+}
+
+func _() {
+L:
+	select {
+	case c <- 1:
+
+	default:
+		goto L
+	}
+}
+
+func _() {
+	select {
+	case <-c:
+
+	default:
+	L:
+		goto L
+	}
+}
+
+func _() {
+	select {
+	case c <- 1:
+
+	default:
+		goto L
+	L:
+	}
+}
+
+func _() {
+	select {
+	case <-c:
+		goto L
+	L:
+		;
+	default:
+	}
+}
+
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	select {
+	case c <- 1:
+	L:
+	}
+}
+
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	select {
+	case c <- 1:
+	L:
+		;
+	default:
+	}
+}
+
+func _() {
+	goto L /* ERROR "goto L jumps into block" */
+	select {
+	case <-c:
+	default:
+	L:
+	}
+}
+
+func _() {
+	select {
+	default:
+		goto L /* ERROR "goto L jumps into block" */
+	case <-c:
+	L:
+	}
+}
+
+func _() {
+	select {
+	case <-c:
+	L:
+		;
+	default:
+		goto L /* ERROR "goto L jumps into block" */
+	}
+}
diff --git a/src/internal/types/testdata/check/importC.go b/src/internal/types/testdata/check/importC.go
new file mode 100644
index 0000000..8078021
--- /dev/null
+++ b/src/internal/types/testdata/check/importC.go
@@ -0,0 +1,56 @@
+// -fakeImportC
+
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package importC
+
+import "C"
+import _ /* ERROR cannot rename import "C" */ "C"
+import foo /* ERROR cannot rename import "C" */ "C"
+import . /* ERROR cannot rename import "C" */ "C"
+
+// Test cases extracted from issue #22090.
+
+import "unsafe"
+
+const _ C.int = 0xff // no error due to invalid constant type
+
+type T struct {
+	Name    string
+	Ordinal int
+}
+
+func _(args []T) {
+	var s string
+	for i, v := range args {
+		cname := C.CString(v.Name)
+		args[i].Ordinal = int(C.sqlite3_bind_parameter_index(s, cname)) // no error due to i not being "used"
+		C.free(unsafe.Pointer(cname))
+	}
+}
+
+type CType C.Type
+
+const _ CType = C.X // no error due to invalid constant type
+const _ = C.X
+
+// Test cases extracted from issue #23712.
+
+func _() {
+	var a [C.ArrayLength]byte
+	_ = a[0] // no index out of bounds error here
+}
+
+// Additional tests to verify fix for #23712.
+
+func _() {
+	var a [C.ArrayLength1]byte
+	_ = 1 / len(a) // no division by zero error here and below
+	_ = 1 / cap(a)
+	_ = uint(unsafe.Sizeof(a)) // must not be negative
+
+	var b [C.ArrayLength2]byte
+	a = b // should be valid
+}
diff --git a/src/internal/types/testdata/check/importdecl0/importdecl0a.go b/src/internal/types/testdata/check/importdecl0/importdecl0a.go
new file mode 100644
index 0000000..d514ae4
--- /dev/null
+++ b/src/internal/types/testdata/check/importdecl0/importdecl0a.go
@@ -0,0 +1,53 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package importdecl0
+
+import ()
+
+import (
+	// we can have multiple blank imports (was bug)
+	_ "math"
+	_ "net/rpc"
+	init /* ERROR "cannot import package as init" */ "fmt"
+	// reflect defines a type "flag" which shows up in the gc export data
+	"reflect"
+	. /* ERROR "imported and not used" */ "reflect"
+)
+
+import "math" /* ERROR "imported and not used" */
+import m /* ERROR "imported as m and not used" */ "math"
+import _ "math"
+
+import (
+	"math/big" /* ERROR "imported and not used" */
+	b /* ERROR "imported as b and not used" */ "math/big"
+	_ "math/big"
+)
+
+import "fmt"
+import f1 "fmt"
+import f2 "fmt"
+
+// reflect.flag must not be visible in this package
+type flag int
+type _ reflect.flag /* ERROR "not exported" */
+
+// imported package name may conflict with local objects
+type reflect /* ERROR "reflect already declared" */ int
+
+// dot-imported exported objects may conflict with local objects
+type Value /* ERROR "Value already declared through dot-import of package reflect" */ struct{}
+
+var _ = fmt.Println // use "fmt"
+
+func _() {
+	f1.Println() // use "fmt"
+}
+
+func _() {
+	_ = func() {
+		f2.Println() // use "fmt"
+	}
+}
diff --git a/src/internal/types/testdata/check/importdecl0/importdecl0b.go b/src/internal/types/testdata/check/importdecl0/importdecl0b.go
new file mode 100644
index 0000000..904faff
--- /dev/null
+++ b/src/internal/types/testdata/check/importdecl0/importdecl0b.go
@@ -0,0 +1,30 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package importdecl0
+
+import "math"
+import m "math"
+
+import . "testing" // declares T in file scope
+import . /* ERROR .unsafe. imported and not used */ "unsafe"
+import . "fmt"     // declares Println in file scope
+
+import (
+	"" /* ERROR invalid import path */
+	"a!b" /* ERROR invalid import path */
+	"abc\xffdef" /* ERROR invalid import path */
+)
+
+// using "math" in this file doesn't affect its use in other files
+const Pi0 = math.Pi
+const Pi1 = m.Pi
+
+type _ T // use "testing"
+
+func _() func() interface{} {
+	return func() interface{} {
+		return Println // use "fmt"
+	}
+}
diff --git a/src/internal/types/testdata/check/importdecl1/importdecl1a.go b/src/internal/types/testdata/check/importdecl1/importdecl1a.go
new file mode 100644
index 0000000..d377c01
--- /dev/null
+++ b/src/internal/types/testdata/check/importdecl1/importdecl1a.go
@@ -0,0 +1,22 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test case for issue 8969.
+
+package importdecl1
+
+import "go/ast"
+import . "unsafe"
+
+var _ Pointer // use dot-imported package unsafe
+
+// Test cases for issue 23914.
+
+type A interface {
+	// Methods m1, m2 must be type-checked in this file scope
+	// even when embedded in an interface in a different
+	// file of the same package.
+	m1() ast.Node
+	m2() Pointer
+}
diff --git a/src/internal/types/testdata/check/importdecl1/importdecl1b.go b/src/internal/types/testdata/check/importdecl1/importdecl1b.go
new file mode 100644
index 0000000..ce8b983
--- /dev/null
+++ b/src/internal/types/testdata/check/importdecl1/importdecl1b.go
@@ -0,0 +1,11 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package importdecl1
+
+import . /* ERROR .unsafe. imported and not used */ "unsafe"
+
+type B interface {
+	A
+}
diff --git a/src/internal/types/testdata/check/init0.go b/src/internal/types/testdata/check/init0.go
new file mode 100644
index 0000000..5159a17
--- /dev/null
+++ b/src/internal/types/testdata/check/init0.go
@@ -0,0 +1,106 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// initialization cycles
+
+package init0
+
+// initialization cycles (we don't know the types)
+const (
+	s0 /* ERROR initialization cycle: s0 refers to itself */ = s0
+
+	x0 /* ERROR initialization cycle for x0 */ = y0
+	y0 = x0
+
+	a0 = b0
+	b0 /* ERROR initialization cycle for b0 */ = c0
+	c0 = d0
+	d0 = b0
+)
+
+var (
+	s1 /* ERROR initialization cycle: s1 refers to itself */ = s1
+
+	x1 /* ERROR initialization cycle for x1 */ = y1
+	y1 = x1
+
+	a1 = b1
+	b1 /* ERROR initialization cycle for b1 */ = c1
+	c1 = d1
+	d1 = b1
+)
+
+// initialization cycles (we know the types)
+const (
+	s2 /* ERROR initialization cycle: s2 refers to itself */ int = s2
+
+	x2 /* ERROR initialization cycle for x2 */ int = y2
+	y2 = x2
+
+	a2 = b2
+	b2 /* ERROR initialization cycle for b2 */ int = c2
+	c2 = d2
+	d2 = b2
+)
+
+var (
+	s3 /* ERROR initialization cycle: s3 refers to itself */ int = s3
+
+	x3 /* ERROR initialization cycle for x3 */ int = y3
+	y3 = x3
+
+	a3 = b3
+	b3 /* ERROR initialization cycle for b3 */ int = c3
+	c3 = d3
+	d3 = b3
+)
+
+// cycles via struct fields
+
+type S1 struct {
+	f int
+}
+const cx3 S1 /* ERROR invalid constant type */ = S1{cx3.f}
+var vx3 /* ERROR initialization cycle: vx3 refers to itself */ S1 = S1{vx3.f}
+
+// cycles via functions
+
+var x4 = x5
+var x5 /* ERROR initialization cycle for x5 */ = f1()
+func f1() int { return x5*10 }
+
+var x6, x7 /* ERROR initialization cycle */ = f2()
+var x8 = x7
+func f2() (int, int) { return f3() + f3(), 0 }
+func f3() int { return x8 }
+
+// cycles via function literals
+
+var x9 /* ERROR initialization cycle: x9 refers to itself */ = func() int { return x9 }()
+
+var x10 /* ERROR initialization cycle for x10 */ = f4()
+
+func f4() int {
+	_ = func() {
+		_ = x10
+	}
+	return 0
+}
+
+// cycles via method expressions
+
+type T1 struct{}
+
+func (T1) m() bool { _ = x11; return false }
+
+var x11 /* ERROR initialization cycle for x11 */ = T1.m(T1{})
+
+// cycles via method values
+
+type T2 struct{}
+
+func (T2) m() bool { _ = x12; return false }
+
+var t1 T2
+var x12 /* ERROR initialization cycle for x12 */ = t1.m
diff --git a/src/internal/types/testdata/check/init1.go b/src/internal/types/testdata/check/init1.go
new file mode 100644
index 0000000..39ca314
--- /dev/null
+++ b/src/internal/types/testdata/check/init1.go
@@ -0,0 +1,97 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// initialization cycles
+
+package init1
+
+// issue 6683 (marked as WorkingAsIntended)
+
+type T0 struct{}
+
+func (T0) m() int { return y0 }
+
+var x0 = T0{}
+
+var y0 /* ERROR initialization cycle */ = x0.m()
+
+type T1 struct{}
+
+func (T1) m() int { return y1 }
+
+var x1 interface {
+	m() int
+} = T1{}
+
+var y1 = x1.m() // no cycle reported, x1 is of interface type
+
+// issue 6703 (modified)
+
+var x2 /* ERROR initialization cycle */ = T2.m
+
+var y2 = x2
+
+type T2 struct{}
+
+func (T2) m() int {
+	_ = y2
+	return 0
+}
+
+var x3 /* ERROR initialization cycle */ = T3.m(T3{}) // <<<< added (T3{})
+
+var y3 = x3
+
+type T3 struct{}
+
+func (T3) m() int {
+	_ = y3
+	return 0
+}
+
+var x4 /* ERROR initialization cycle */ = T4{}.m // <<<< added {}
+
+var y4 = x4
+
+type T4 struct{}
+
+func (T4) m() int {
+	_ = y4
+	return 0
+}
+
+var x5 /* ERROR initialization cycle */ = T5{}.m() // <<<< added ()
+
+var y5 = x5
+
+type T5 struct{}
+
+func (T5) m() int {
+	_ = y5
+	return 0
+}
+
+// issue 4847
+// simplified test case
+
+var x6 = f6
+var y6 /* ERROR initialization cycle */ = f6
+func f6() { _ = y6 }
+
+// full test case
+
+type (
+      E int
+      S int
+)
+
+type matcher func(s *S) E
+
+func matchList(s *S) E { return matcher(matchAnyFn)(s) }
+
+var foo = matcher(matchList)
+
+var matchAny /* ERROR initialization cycle */ = matcher(matchList)
+
+func matchAnyFn(s *S) (err E) { return matchAny(s) }
\ No newline at end of file
diff --git a/src/internal/types/testdata/check/init2.go b/src/internal/types/testdata/check/init2.go
new file mode 100644
index 0000000..614db6c
--- /dev/null
+++ b/src/internal/types/testdata/check/init2.go
@@ -0,0 +1,139 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// initialization cycles
+
+package init2
+
+// cycles through functions
+
+func f1() int { _ = x1; return 0 }
+var x1 /* ERROR initialization cycle */ = f1
+
+func f2() int { _ = x2; return 0 }
+var x2 /* ERROR initialization cycle */ = f2()
+
+// cycles through method expressions
+
+type T3 int
+func (T3) m() int { _ = x3; return 0 }
+var x3 /* ERROR initialization cycle */ = T3.m
+
+type T4 int
+func (T4) m() int { _ = x4; return 0 }
+var x4 /* ERROR initialization cycle */ = T4.m(0)
+
+type T3p int
+func (*T3p) m() int { _ = x3p; return 0 }
+var x3p /* ERROR initialization cycle */ = (*T3p).m
+
+type T4p int
+func (*T4p) m() int { _ = x4p; return 0 }
+var x4p /* ERROR initialization cycle */ = (*T4p).m(nil)
+
+// cycles through method expressions of embedded methods
+
+type T5 struct { E5 }
+type E5 int
+func (E5) m() int { _ = x5; return 0 }
+var x5 /* ERROR initialization cycle */ = T5.m
+
+type T6 struct { E6 }
+type E6 int
+func (E6) m() int { _ = x6; return 0 }
+var x6 /* ERROR initialization cycle */ = T6.m(T6{0})
+
+type T5p struct { E5p }
+type E5p int
+func (*E5p) m() int { _ = x5p; return 0 }
+var x5p /* ERROR initialization cycle */ = (*T5p).m
+
+type T6p struct { E6p }
+type E6p int
+func (*E6p) m() int { _ = x6p; return 0 }
+var x6p /* ERROR initialization cycle */ = (*T6p).m(nil)
+
+// cycles through method values
+
+type T7 int
+func (T7) m() int { _ = x7; return 0 }
+var x7 /* ERROR initialization cycle */ = T7(0).m
+
+type T8 int
+func (T8) m() int { _ = x8; return 0 }
+var x8 /* ERROR initialization cycle */ = T8(0).m()
+
+type T7p int
+func (*T7p) m() int { _ = x7p; return 0 }
+var x7p /* ERROR initialization cycle */ = new(T7p).m
+
+type T8p int
+func (*T8p) m() int { _ = x8p; return 0 }
+var x8p /* ERROR initialization cycle */ = new(T8p).m()
+
+type T7v int
+func (T7v) m() int { _ = x7v; return 0 }
+var x7var T7v
+var x7v /* ERROR initialization cycle */ = x7var.m
+
+type T8v int
+func (T8v) m() int { _ = x8v; return 0 }
+var x8var T8v
+var x8v /* ERROR initialization cycle */ = x8var.m()
+
+type T7pv int
+func (*T7pv) m() int { _ = x7pv; return 0 }
+var x7pvar *T7pv
+var x7pv /* ERROR initialization cycle */ = x7pvar.m
+
+type T8pv int
+func (*T8pv) m() int { _ = x8pv; return 0 }
+var x8pvar *T8pv
+var x8pv /* ERROR initialization cycle */ = x8pvar.m()
+
+// cycles through method values of embedded methods
+
+type T9 struct { E9 }
+type E9 int
+func (E9) m() int { _ = x9; return 0 }
+var x9 /* ERROR initialization cycle */ = T9{0}.m
+
+type T10 struct { E10 }
+type E10 int
+func (E10) m() int { _ = x10; return 0 }
+var x10 /* ERROR initialization cycle */ = T10{0}.m()
+
+type T9p struct { E9p }
+type E9p int
+func (*E9p) m() int { _ = x9p; return 0 }
+var x9p /* ERROR initialization cycle */ = new(T9p).m
+
+type T10p struct { E10p }
+type E10p int
+func (*E10p) m() int { _ = x10p; return 0 }
+var x10p /* ERROR initialization cycle */ = new(T10p).m()
+
+type T9v struct { E9v }
+type E9v int
+func (E9v) m() int { _ = x9v; return 0 }
+var x9var T9v
+var x9v /* ERROR initialization cycle */ = x9var.m
+
+type T10v struct { E10v }
+type E10v int
+func (E10v) m() int { _ = x10v; return 0 }
+var x10var T10v
+var x10v /* ERROR initialization cycle */ = x10var.m()
+
+type T9pv struct { E9pv }
+type E9pv int
+func (*E9pv) m() int { _ = x9pv; return 0 }
+var x9pvar *T9pv
+var x9pv /* ERROR initialization cycle */ = x9pvar.m
+
+type T10pv struct { E10pv }
+type E10pv int
+func (*E10pv) m() int { _ = x10pv; return 0 }
+var x10pvar *T10pv
+var x10pv /* ERROR initialization cycle */ = x10pvar.m()
diff --git a/src/internal/types/testdata/check/issue25008/issue25008a.go b/src/internal/types/testdata/check/issue25008/issue25008a.go
new file mode 100644
index 0000000..cf71ca1
--- /dev/null
+++ b/src/internal/types/testdata/check/issue25008/issue25008a.go
@@ -0,0 +1,15 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "io"
+
+type A interface {
+        io.Reader
+}
+
+func f(a A) {
+        a.Read(nil)
+}
diff --git a/src/internal/types/testdata/check/issue25008/issue25008b.go b/src/internal/types/testdata/check/issue25008/issue25008b.go
new file mode 100644
index 0000000..f132b7f
--- /dev/null
+++ b/src/internal/types/testdata/check/issue25008/issue25008b.go
@@ -0,0 +1,9 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type B interface {
+    A
+}
diff --git a/src/internal/types/testdata/check/issues0.go b/src/internal/types/testdata/check/issues0.go
new file mode 100644
index 0000000..4a66641
--- /dev/null
+++ b/src/internal/types/testdata/check/issues0.go
@@ -0,0 +1,373 @@
+// -lang=go1.17
+
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p // don't permit non-interface elements in interfaces
+
+import (
+	"fmt"
+	syn "regexp/syntax"
+	t1 "text/template"
+	t2 "html/template"
+)
+
+func issue7035() {
+	type T struct{ X int }
+	_ = func() {
+		fmt.Println() // must refer to imported fmt rather than the fmt below
+	}
+	fmt := new(T)
+	_ = fmt.X
+}
+
+func issue8066() {
+	const (
+		_ = float32(340282356779733661637539395458142568447)
+		_ = float32(340282356779733661637539395458142568448 /* ERROR cannot convert */ )
+	)
+}
+
+// Check that a missing identifier doesn't lead to a spurious error cascade.
+func issue8799a() {
+	x, ok := missing /* ERROR undefined */ ()
+	_ = !ok
+	_ = x
+}
+
+func issue8799b(x int, ok bool) {
+	x, ok = missing /* ERROR undefined */ ()
+	_ = !ok
+	_ = x
+}
+
+func issue9182() {
+	type Point C /* ERROR undefined */ .Point
+	// no error for composite literal based on unknown type
+	_ = Point{x: 1, y: 2}
+}
+
+func f0() (a []int)         { return }
+func f1() (a []int, b int)  { return }
+func f2() (a, b []int)      { return }
+
+func append_([]int, ...int) {}
+
+func issue9473(a []int, b ...int) {
+	// variadic builtin function
+	_ = append(f0())
+	_ = append(f0(), f0()...)
+	_ = append(f1())
+	_ = append(f2 /* ERROR cannot use .* in argument */ ())
+	_ = append(f2()... /* ERROR cannot use ... */ )
+	_ = append(f0(), f1 /* ERROR multiple-value f1 */ ())
+	_ = append(f0(), f2 /* ERROR multiple-value f2 */ ())
+	_ = append(f0(), f1 /* ERROR multiple-value f1 */ ()...)
+	_ = append(f0(), f2 /* ERROR multiple-value f2 */ ()...)
+
+	// variadic user-defined function
+	append_(f0())
+	append_(f0(), f0()...)
+	append_(f1())
+	append_(f2 /* ERROR cannot use .* in argument */ ())
+	append_(f2()... /* ERROR cannot use ... */ )
+	append_(f0(), f1 /* ERROR multiple-value f1 */ ())
+	append_(f0(), f2 /* ERROR multiple-value f2 */ ())
+	append_(f0(), f1 /* ERROR multiple-value f1 */ ()...)
+	append_(f0(), f2 /* ERROR multiple-value f2 */ ()...)
+}
+
+// Check that embedding a non-interface type in an interface results in a good error message.
+func issue10979() {
+	type _ interface {
+		int /* ERROR non-interface type int */
+	}
+	type T struct{}
+	type _ interface {
+		T /* ERROR non-interface type T */
+	}
+	type _ interface {
+		nosuchtype /* ERROR undefined: nosuchtype */
+	}
+	type _ interface {
+		fmt.Nosuchtype /* ERROR undefined: fmt\.Nosuchtype */
+	}
+	type _ interface {
+		nosuchpkg /* ERROR undefined: nosuchpkg */ .Nosuchtype
+	}
+	type I interface {
+		I.m /* ERROR I.m is not a type */
+		m()
+	}
+}
+
+// issue11347
+// These should not crash.
+var a1, b1 /* ERROR cycle */ , c1 /* ERROR cycle */ b1 = 0 > 0<<""[""[c1]]>c1
+var a2, b2 /* ERROR cycle */ = 0 /* ERROR assignment mismatch */ /* ERROR assignment mismatch */ > 0<<""[b2]
+var a3, b3 /* ERROR cycle */ = int /* ERROR assignment mismatch */ /* ERROR assignment mismatch */ (1<<""[b3])
+
+// issue10260
+// Check that error messages explain reason for interface assignment failures.
+type (
+	I0 interface{}
+	I1 interface{ foo() }
+	I2 interface{ foo(x int) }
+	T0 struct{}
+	T1 struct{}
+	T2 struct{}
+)
+
+func (*T1) foo() {}
+func (*T2) foo(x int) {}
+
+func issue10260() {
+	var (
+		i0 I0
+		i1 I1
+		i2 I2
+		t0 *T0
+		t1 *T1
+		t2 *T2
+	)
+
+	var x I1
+	x = T1 /* ERROR cannot use T1{} .* as I1 value in assignment: T1 does not implement I1 \(method foo has pointer receiver\) */ {}
+	_ = x /* ERROR impossible type assertion: x\.\(T1\)\n\tT1 does not implement I1 \(method foo has pointer receiver\) */ .(T1)
+
+	T1{}.foo /* ERROR cannot call pointer method foo on T1 */ ()
+	x.Foo /* ERROR "x.Foo undefined \(type I1 has no field or method Foo, but does have foo\)" */ ()
+
+	_ = i2 /* ERROR impossible type assertion: i2\.\(\*T1\)\n\t\*T1 does not implement I2 \(wrong type for method foo\)\n\t\thave foo\(\)\n\t\twant foo\(int\) */ .(*T1)
+
+	i1 = i0 /* ERROR cannot use i0 .* as I1 value in assignment: I0 does not implement I1 \(missing method foo\) */
+	i1 = t0 /* ERROR .* t0 .* as I1 .*: \*T0 does not implement I1 \(missing method foo\) */
+	i1 = i2 /* ERROR .* i2 .* as I1 .*: I2 does not implement I1 \(wrong type for method foo\)\n\t\thave foo\(int\)\n\t\twant foo\(\) */
+	i1 = t2 /* ERROR .* t2 .* as I1 .*: \*T2 does not implement I1 \(wrong type for method foo\)\n\t\thave foo\(int\)\n\t\twant foo\(\) */
+	i2 = i1 /* ERROR .* i1 .* as I2 .*: I1 does not implement I2 \(wrong type for method foo\)\n\t\thave foo\(\)\n\t\twant foo\(int\) */
+	i2 = t1 /* ERROR .* t1 .* as I2 .*: \*T1 does not implement I2 \(wrong type for method foo\)\n\t\thave foo\(\)\n\t\twant foo\(int\) */
+
+	_ = func() I1 { return i0 /* ERROR cannot use i0 .* as I1 value in return statement: I0 does not implement I1 \(missing method foo\) */ }
+	_ = func() I1 { return t0 /* ERROR .* t0 .* as I1 .*: \*T0 does not implement I1 \(missing method foo\) */ }
+	_ = func() I1 { return i2 /* ERROR .* i2 .* as I1 .*: I2 does not implement I1 \(wrong type for method foo\)\n\t\thave foo\(int\)\n\t\twant foo\(\) */ }
+	_ = func() I1 { return t2 /* ERROR .* t2 .* as I1 .*: \*T2 does not implement I1 \(wrong type for method foo\)\n\t\thave foo\(int\)\n\t\twant foo\(\) */ }
+	_ = func() I2 { return i1 /* ERROR .* i1 .* as I2 .*: I1 does not implement I2 \(wrong type for method foo\)\n\t\thave foo\(\)\n\t\twant foo\(int\) */ }
+	_ = func() I2 { return t1 /* ERROR .* t1 .* as I2 .*: \*T1 does not implement I2 \(wrong type for method foo\)\n\t\thave foo\(\)\n\t\twant foo\(int\) */ }
+
+	// a few more - less exhaustive now
+
+	f := func(I1, I2){}
+	f(i0 /* ERROR missing method foo */ , i1 /* ERROR wrong type for method foo */ )
+
+	_ = [...]I1{i0 /* ERROR cannot use i0 .* as I1 value in array or slice literal: I0 does not implement I1 \(missing method foo\) */ }
+	_ = [...]I1{i2 /* ERROR cannot use i2 .* as I1 value in array or slice literal: I2 does not implement I1 \(wrong type for method foo\)\n\t\thave foo\(int\)\n\t\twant foo\(\) */ }
+	_ = []I1{i0 /* ERROR missing method foo */ }
+	_ = []I1{i2 /* ERROR wrong type for method foo */ }
+	_ = map[int]I1{0: i0 /* ERROR missing method foo */ }
+	_ = map[int]I1{0: i2 /* ERROR wrong type for method foo */ }
+
+	make(chan I1) <- i0 /* ERROR missing method foo */
+	make(chan I1) <- i2 /* ERROR wrong type for method foo */
+}
+
+// Check that constants representable as integers are in integer form
+// before being used in operations that are only defined on integers.
+func issue14229() {
+	// from the issue
+	const _ = int64(-1<<63) % 1e6
+
+	// related
+	const (
+		a int = 3
+		b = 4.0
+		_ = a / b
+		_ = a % b
+		_ = b / a
+		_ = b % a
+	)
+}
+
+// Check that in a n:1 variable declaration with type and initialization
+// expression the type is distributed to all variables of the lhs before
+// the initialization expression assignment is checked.
+func issue15755() {
+	// from issue
+	var i interface{}
+	type b bool
+	var x, y b = i.(b)
+	_ = x == y
+
+	// related: we should see an error since the result of f1 is ([]int, int)
+	var u, v []int = f1 /* ERROR cannot use f1 */ ()
+	_ = u
+	_ = v
+}
+
+// Test that we don't get "declared and not used"
+// errors in the context of invalid/C objects.
+func issue20358() {
+	var F C /* ERROR "undefined" */ .F
+	var A C /* ERROR "undefined" */ .A
+	var S C /* ERROR "undefined" */ .S
+	type T C /* ERROR "undefined" */ .T
+	type P C /* ERROR "undefined" */ .P
+
+	// these variables must be "used" even though
+	// the LHS expressions/types below in which
+	// context they are used are unknown/invalid
+	var f, a, s1, s2, s3, t, p int
+
+	_ = F(f)
+	_ = A[a]
+	_ = S[s1:s2:s3]
+	_ = T{t}
+	_ = P{f: p}
+}
+
+// Test that we don't declare lhs variables in short variable
+// declarations before we type-check function literals on the
+// rhs.
+func issue24026() {
+	f := func() int { f(0) /* must refer to outer f */; return 0 }
+	_ = f
+
+	_ = func() {
+		f := func() { _ = f() /* must refer to outer f */ }
+		_ = f
+	}
+
+	// b and c must not be visible inside function literal
+	a := 0
+	a, b, c := func() (int, int, int) {
+		return a, b /* ERROR undefined */ , c /* ERROR undefined */
+	}()
+	_, _ = b, c
+}
+
+func f(int) {} // for issue24026
+
+// Test that we don't report a "missing return statement" error
+// (due to incorrect context when type-checking interfaces).
+func issue24140(x interface{}) int {
+        switch x.(type) {
+        case interface{}:
+                return 0
+        default:
+                panic(0)
+        }
+}
+
+// Test that we don't crash when the 'if' condition is missing.
+func issue25438() {
+	if { /* ERROR missing condition */ }
+	if x := 0; /* ERROR missing condition */ { _ = x }
+	if
+	{ /* ERROR missing condition */ }
+}
+
+// Test that we can embed alias type names in interfaces.
+type issue25301 interface {
+	E
+}
+
+type E = interface {
+	m()
+}
+
+// Test case from issue.
+// cmd/compile reports a cycle as well.
+type issue25301b /* ERROR invalid recursive type */ = interface {
+	m() interface{ issue25301b }
+}
+
+type issue25301c interface {
+	notE // ERROR non-interface type struct\{\}
+}
+
+type notE = struct{}
+
+// Test that method declarations don't introduce artificial cycles
+// (issue #26124).
+const CC TT = 1
+type TT int
+func (TT) MM() [CC]TT
+
+// Reduced test case from issue #26124.
+const preloadLimit LNumber = 128
+type LNumber float64
+func (LNumber) assertFunction() *LFunction
+type LFunction struct {
+	GFunction LGFunction
+}
+type LGFunction func(*LState)
+type LState struct {
+	reg *registry
+}
+type registry struct {
+	alloc *allocator
+}
+type allocator struct {
+	_ [int(preloadLimit)]int
+}
+
+// Test that we don't crash when type-checking composite literals
+// containing errors in the type.
+var issue27346 = [][n /* ERROR undefined */ ]int{
+	0: {},
+}
+
+var issue22467 = map[int][... /* ERROR invalid use of ... */ ]int{0: {}}
+
+// Test that invalid use of ... in parameter lists is recognized
+// (issue #28281).
+func issue28281a(int, int, ...int)
+func issue28281b(a, b int, c ...int)
+func issue28281c(a, b, c ... /* ERROR can only use ... with final parameter */ int)
+func issue28281d(... /* ERROR can only use ... with final parameter */ int, int)
+func issue28281e(a, b, c  ... /* ERROR can only use ... with final parameter */ int, d int)
+func issue28281f(... /* ERROR can only use ... with final parameter */ int, ... /* ERROR can only use ... with final parameter */ int, int)
+func (... /* ERROR can only use ... with final parameter */ TT) f()
+func issue28281g() (... /* ERROR can only use ... with final parameter */ TT)
+
+// Issue #26234: Make various field/method lookup errors easier to read by matching cmd/compile's output
+func issue26234a(f *syn.Prog) {
+	// The error message below should refer to the actual package name (syntax)
+	// not the local package name (syn).
+	f.foo /* ERROR f\.foo undefined \(type \*syntax\.Prog has no field or method foo\) */
+}
+
+type T struct {
+	x int
+	E1
+	E2
+}
+
+type E1 struct{ f int }
+type E2 struct{ f int }
+
+func issue26234b(x T) {
+	_ = x.f /* ERROR ambiguous selector x.f */
+}
+
+func issue26234c() {
+	T.x /* ERROR T.x undefined \(type T has no method x\) */ ()
+}
+
+func issue35895() {
+	// T is defined in this package, don't qualify its name with the package name.
+	var _ T = 0 // ERROR cannot use 0 \(untyped int constant\) as T
+
+	// There is only one package with name syntax imported, only use the (global) package name in error messages.
+	var _ *syn.Prog = 0 // ERROR cannot use 0 \(untyped int constant\) as \*syntax.Prog
+
+	// Because both t1 and t2 have the same global package name (template),
+	// qualify packages with full path name in this case.
+	var _ t1.Template = t2 /* ERROR cannot use .* \(value of type .html/template.\.Template\) as .text/template.\.Template */ .Template{}
+}
+
+func issue42989(s uint) {
+	var m map[int]string
+	delete(m, 1<<s)
+	delete(m, 1.<<s)
+}
diff --git a/src/internal/types/testdata/check/issues1.go b/src/internal/types/testdata/check/issues1.go
new file mode 100644
index 0000000..2f3414d
--- /dev/null
+++ b/src/internal/types/testdata/check/issues1.go
@@ -0,0 +1,252 @@
+// -oldComparableSemantics
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file contains regression tests for bugs found.
+
+package p
+
+import "io"
+import "context"
+
+func eql[T comparable](x, y T) bool {
+	return x == y
+}
+
+func _[X comparable, Y interface{comparable; m()}]() {
+	var x X
+	var y Y
+	eql(x, y /* ERROR does not match */ ) // interfaces of different types
+	eql(x, x)
+	eql(y, y)
+	eql(y, nil /* ERROR cannot use nil as Y value in argument to eql */ )
+	eql[io /* ERROR does not satisfy comparable */ .Reader](nil, nil)
+}
+
+// If we have a receiver of pointer to type parameter type (below: *T)
+// we don't have any methods, like for interfaces.
+type C[T any] interface {
+    m()
+}
+
+// using type bound C
+func _[T C[T]](x *T) {
+	x.m /* ERROR x\.m undefined */ ()
+}
+
+// using an interface literal as bound
+func _[T interface{ m() }](x *T) {
+	x.m /* ERROR x\.m undefined */ ()
+}
+
+func f2[_ interface{ m1(); m2() }]() {}
+
+type T struct{}
+func (T) m1()
+func (*T) m2()
+
+func _() {
+	f2[T /* ERROR m2 has pointer receiver */ ]()
+	f2[*T]()
+}
+
+// When a type parameter is used as an argument to instantiate a parameterized
+// type, the type argument's type set must be a subset of the instantiated type
+// parameter's type set.
+type T1[P interface{~uint}] struct{}
+
+func _[P any]() {
+    _ = T1[P /* ERROR P does not satisfy interface{~uint} */ ]{}
+}
+
+// This is the original (simplified) program causing the same issue.
+type Unsigned interface {
+	~uint
+}
+
+type T2[U Unsigned] struct {
+    s U
+}
+
+func (u T2[U]) Add1() U {
+    return u.s + 1
+}
+
+func NewT2[U any]() T2[U /* ERROR U does not satisfy Unsigned */ ] {
+    return T2[U /* ERROR U does not satisfy Unsigned */ ]{}
+}
+
+func _() {
+    u := NewT2[string]()
+    _ = u.Add1()
+}
+
+// When we encounter an instantiated type such as Elem[T] we must
+// not "expand" the instantiation when the type to be instantiated
+// (Elem in this case) is not yet fully set up.
+type Elem[T any] struct {
+	next *Elem[T]
+	list *List[T]
+}
+
+type List[T any] struct {
+	root Elem[T]
+}
+
+func (l *List[T]) Init() {
+	l.root.next = &l.root
+}
+
+// This is the original program causing the same issue.
+type Element2[TElem any] struct {
+	next, prev *Element2[TElem]
+	list *List2[TElem]
+	Value TElem
+}
+
+type List2[TElem any] struct {
+	root Element2[TElem]
+	len  int
+}
+
+func (l *List2[TElem]) Init() *List2[TElem] {
+	l.root.next = &l.root
+	l.root.prev = &l.root
+	l.len = 0
+	return l
+}
+
+// Self-recursive instantiations must work correctly.
+type A[P any] struct { _ *A[P] }
+
+type AB[P any] struct { _ *BA[P] }
+type BA[P any] struct { _ *AB[P] }
+
+// And a variation that also caused a problem with an
+// unresolved underlying type.
+type Element3[TElem any] struct {
+	next, prev *Element3[TElem]
+	list *List3[TElem]
+	Value TElem
+}
+
+func (e *Element3[TElem]) Next() *Element3[TElem] {
+	if p := e.next; e.list != nil && p != &e.list.root {
+		return p
+	}
+	return nil
+}
+
+type List3[TElem any] struct {
+	root Element3[TElem]
+	len  int
+}
+
+// Infinite generic type declarations must lead to an error.
+type inf1[T any] struct{ _ inf1 /* ERROR invalid recursive type */ [T] }
+type inf2[T any] struct{ inf2 /* ERROR invalid recursive type */ [T] }
+
+// The implementation of conversions T(x) between integers and floating-point
+// numbers checks that both T and x have either integer or floating-point
+// type. When the type of T or x is a type parameter, the respective simple
+// predicate disjunction in the implementation was wrong because if a type set
+// contains both an integer and a floating-point type, the type parameter is
+// neither an integer or a floating-point number.
+func convert[T1, T2 interface{~int | ~uint | ~float32}](v T1) T2 {
+	return T2(v)
+}
+
+func _() {
+	convert[int, uint](5)
+}
+
+// When testing binary operators, for +, the operand types must either be
+// both numeric, or both strings. The implementation had the same problem
+// with this check as the conversion issue above (issue #39623).
+
+func issue39623[T interface{~int | ~string}](x, y T) T {
+	return x + y
+}
+
+// Simplified, from https://go2goplay.golang.org/p/efS6x6s-9NI:
+func Sum[T interface{~int | ~string}](s []T) (sum T) {
+	for _, v := range s {
+		sum += v
+	}
+	return
+}
+
+// Assignability of an unnamed pointer type to a type parameter that
+// has a matching underlying type.
+func _[T interface{}, PT interface{~*T}] (x T) PT {
+    return &x
+}
+
+// Indexing of type parameters containing type parameters in their constraint terms:
+func at[T interface{ ~[]E }, E interface{}](x T, i int) E {
+        return x[i]
+}
+
+// Conversion of a local type to a type parameter.
+func _[T interface{~int}](x T) {
+	type myint int
+	var _ int = int(x)
+	var _ T = 42
+	var _ T = T(myint(42))
+}
+
+// Indexing a type parameter with an array type bound checks length.
+// (Example by mdempsky@.)
+func _[T interface { ~[10]int }](x T) {
+	_ = x[9] // ok
+	_ = x[20 /* ERROR out of bounds */ ]
+}
+
+// Pointer indirection of a type parameter.
+func _[T interface{ ~*int }](p T) int {
+	return *p
+}
+
+// Channel sends and receives on type parameters.
+func _[T interface{ ~chan int }](ch T) int {
+	ch <- 0
+	return <- ch
+}
+
+// Calling of a generic variable.
+func _[T interface{ ~func() }](f T) {
+	f()
+	go f()
+}
+
+type F1 func()
+type F2 func()
+func _[T interface{ func()|F1|F2 }](f T) {
+	f()
+	go f()
+}
+
+// We must compare against the (possibly underlying) types of term list
+// elements when checking if a constraint is satisfied by a type.
+// The underlying type of each term must be computed after the
+// interface has been instantiated as its constraint may contain
+// a type parameter that was substituted with a defined type.
+// Test case from an (originally) failing example.
+
+type sliceOf[E any] interface{ ~[]E }
+
+func append[T interface{}, S sliceOf[T], T2 interface{}](s S, t ...T2) S { panic(0) }
+
+var f           func()
+var cancelSlice []context.CancelFunc
+var _ = append[context.CancelFunc, []context.CancelFunc, context.CancelFunc](cancelSlice, f)
+
+// A generic function must be instantiated with a type, not a value.
+
+func g[T any](T) T { panic(0) }
+
+var _ = g[int]
+var _ = g[nil /* ERROR is not a type */ ]
+var _ = g(0)
diff --git a/src/internal/types/testdata/check/labels.go b/src/internal/types/testdata/check/labels.go
new file mode 100644
index 0000000..5948952
--- /dev/null
+++ b/src/internal/types/testdata/check/labels.go
@@ -0,0 +1,207 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file is a modified concatenation of the files
+// $GOROOT/test/label.go and $GOROOT/test/label1.go.
+
+package labels
+
+var x int
+
+func f0() {
+L1 /* ERROR "label L1 declared and not used" */ :
+	for {
+	}
+L2 /* ERROR "label L2 declared and not used" */ :
+	select {
+	}
+L3 /* ERROR "label L3 declared and not used" */ :
+	switch {
+	}
+L4 /* ERROR "label L4 declared and not used" */ :
+	if true {
+	}
+L5 /* ERROR "label L5 declared and not used" */ :
+	f0()
+L6:
+	f0()
+L6 /* ERROR "label L6 already declared" */ :
+	f0()
+	if x == 20 {
+		goto L6
+	}
+
+L7:
+	for {
+		break L7
+		break L8 /* ERROR "invalid break label L8" */
+	}
+
+// A label must be directly associated with a switch, select, or
+// for statement; it cannot be the label of a labeled statement.
+
+L7a /* ERROR "declared and not used" */ : L7b:
+	for {
+		break L7a /* ERROR "invalid break label L7a" */
+		continue L7a /* ERROR "invalid continue label L7a" */
+		continue L7b
+	}
+
+L8:
+	for {
+		if x == 21 {
+			continue L8
+			continue L7 /* ERROR "invalid continue label L7" */
+		}
+	}
+
+L9:
+	switch {
+	case true:
+		break L9
+	defalt /* ERROR "label defalt declared and not used" */ :
+	}
+
+L10:
+	select {
+	default:
+		break L10
+		break L9 /* ERROR "invalid break label L9" */
+	}
+
+	goto L10a
+L10a: L10b:
+	select {
+	default:
+		break L10a /* ERROR "invalid break label L10a" */
+		break L10b
+		continue L10b /* ERROR "invalid continue label L10b" */
+	}
+}
+
+func f1() {
+L1:
+	for {
+		if x == 0 {
+			break L1
+		}
+		if x == 1 {
+			continue L1
+		}
+		goto L1
+	}
+
+L2:
+	select {
+	default:
+		if x == 0 {
+			break L2
+		}
+		if x == 1 {
+			continue L2 /* ERROR "invalid continue label L2" */
+		}
+		goto L2
+	}
+
+L3:
+	switch {
+	case x > 10:
+		if x == 11 {
+			break L3
+		}
+		if x == 12 {
+			continue L3 /* ERROR "invalid continue label L3" */
+		}
+		goto L3
+	}
+
+L4:
+	if true {
+		if x == 13 {
+			break L4 /* ERROR "invalid break label L4" */
+		}
+		if x == 14 {
+			continue L4 /* ERROR "invalid continue label L4" */
+		}
+		if x == 15 {
+			goto L4
+		}
+	}
+
+L5:
+	f1()
+	if x == 16 {
+		break L5 /* ERROR "invalid break label L5" */
+	}
+	if x == 17 {
+		continue L5 /* ERROR "invalid continue label L5" */
+	}
+	if x == 18 {
+		goto L5
+	}
+
+	for {
+		if x == 19 {
+			break L1 /* ERROR "invalid break label L1" */
+		}
+		if x == 20 {
+			continue L1 /* ERROR "invalid continue label L1" */
+		}
+		if x == 21 {
+			goto L1
+		}
+	}
+}
+
+// Additional tests not in the original files.
+
+func f2() {
+L1 /* ERROR "label L1 declared and not used" */ :
+	if x == 0 {
+		for {
+			continue L1 /* ERROR "invalid continue label L1" */
+		}
+	}
+}
+
+func f3() {
+L1:
+L2:
+L3:
+	for {
+		break L1 /* ERROR "invalid break label L1" */
+		break L2 /* ERROR "invalid break label L2" */
+		break L3
+		continue L1 /* ERROR "invalid continue label L1" */
+		continue L2 /* ERROR "invalid continue label L2" */
+		continue L3
+		goto L1
+		goto L2
+		goto L3
+	}
+}
+
+// Blank labels are never declared.
+
+func f4() {
+_:
+_: // multiple blank labels are ok
+	goto _ /* ERROR "label _ not declared" */
+}
+
+func f5() {
+_:
+	for {
+		break _ /* ERROR "invalid break label _" */
+		continue _ /* ERROR "invalid continue label _" */
+	}
+}
+
+func f6() {
+_:
+	switch {
+	default:
+		break _ /* ERROR "invalid break label _" */
+	}
+}
diff --git a/src/internal/types/testdata/check/linalg.go b/src/internal/types/testdata/check/linalg.go
new file mode 100644
index 0000000..f02e773
--- /dev/null
+++ b/src/internal/types/testdata/check/linalg.go
@@ -0,0 +1,82 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package linalg
+
+// Numeric is type bound that matches any numeric type.
+// It would likely be in a constraints package in the standard library.
+type Numeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
+		~float32 | ~float64 |
+		~complex64 | ~complex128
+}
+
+func DotProduct[T Numeric](s1, s2 []T) T {
+	if len(s1) != len(s2) {
+		panic("DotProduct: slices of unequal length")
+	}
+	var r T
+	for i := range s1 {
+		r += s1[i] * s2[i]
+	}
+	return r
+}
+
+// NumericAbs matches numeric types with an Abs method.
+type NumericAbs[T any] interface {
+	Numeric
+
+	Abs() T
+}
+
+// AbsDifference computes the absolute value of the difference of
+// a and b, where the absolute value is determined by the Abs method.
+func AbsDifference[T NumericAbs[T]](a, b T) T {
+	d := a - b
+	return d.Abs()
+}
+
+// OrderedNumeric is a type bound that matches numeric types that support the < operator.
+type OrderedNumeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
+		~float32 | ~float64
+}
+
+// Complex is a type bound that matches the two complex types, which do not have a < operator.
+type Complex interface {
+	~complex64 | ~complex128
+}
+
+// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
+// // OrderedAbs is a helper type that defines an Abs method for
+// // ordered numeric types.
+// type OrderedAbs[T OrderedNumeric] T
+// 
+// func (a OrderedAbs[T]) Abs() OrderedAbs[T] {
+// 	if a < 0 {
+// 		return -a
+// 	}
+// 	return a
+// }
+// 
+// // ComplexAbs is a helper type that defines an Abs method for
+// // complex types.
+// type ComplexAbs[T Complex] T
+// 
+// func (a ComplexAbs[T]) Abs() ComplexAbs[T] {
+// 	r := float64(real(a))
+// 	i := float64(imag(a))
+// 	d := math.Sqrt(r * r + i * i)
+// 	return ComplexAbs[T](complex(d, 0))
+// }
+// 
+// func OrderedAbsDifference[T OrderedNumeric](a, b T) T {
+// 	return T(AbsDifference(OrderedAbs[T](a), OrderedAbs[T](b)))
+// }
+// 
+// func ComplexAbsDifference[T Complex](a, b T) T {
+// 	return T(AbsDifference(ComplexAbs[T](a), ComplexAbs[T](b)))
+// }
diff --git a/src/internal/types/testdata/check/literals.go b/src/internal/types/testdata/check/literals.go
new file mode 100644
index 0000000..494a465
--- /dev/null
+++ b/src/internal/types/testdata/check/literals.go
@@ -0,0 +1,111 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file tests various representations of literals
+// and compares them with literals or constant expressions
+// of equal values.
+
+package literals
+
+func _() {
+	// 0-octals
+	assert(0_123 == 0123)
+	assert(0123_456 == 0123456)
+
+	// decimals
+	assert(1_234 == 1234)
+	assert(1_234_567 == 1234567)
+
+	// hexadecimals
+	assert(0X_0 == 0)
+	assert(0X_1234 == 0x1234)
+	assert(0X_CAFE_f00d == 0xcafef00d)
+
+	// octals
+	assert(0o0 == 0)
+	assert(0o1234 == 01234)
+	assert(0o01234567 == 01234567)
+
+	assert(0O0 == 0)
+	assert(0O1234 == 01234)
+	assert(0O01234567 == 01234567)
+
+	assert(0o_0 == 0)
+	assert(0o_1234 == 01234)
+	assert(0o0123_4567 == 01234567)
+
+	assert(0O_0 == 0)
+	assert(0O_1234 == 01234)
+	assert(0O0123_4567 == 01234567)
+
+	// binaries
+	assert(0b0 == 0)
+	assert(0b1011 == 0xb)
+	assert(0b00101101 == 0x2d)
+
+	assert(0B0 == 0)
+	assert(0B1011 == 0xb)
+	assert(0B00101101 == 0x2d)
+
+	assert(0b_0 == 0)
+	assert(0b10_11 == 0xb)
+	assert(0b_0010_1101 == 0x2d)
+
+	// decimal floats
+	assert(1_2_3. == 123.)
+	assert(0_123. == 123.)
+
+	assert(0_0e0 == 0.)
+	assert(1_2_3e0 == 123.)
+	assert(0_123e0 == 123.)
+
+	assert(0e-0_0 == 0.)
+	assert(1_2_3E+0 == 123.)
+	assert(0123E1_2_3 == 123e123)
+
+	assert(0.e+1 == 0.)
+	assert(123.E-1_0 == 123e-10)
+	assert(01_23.e123 == 123e123)
+
+	assert(.0e-1 == .0)
+	assert(.123E+10 == .123e10)
+	assert(.0123E123 == .0123e123)
+
+	assert(1_2_3.123 == 123.123)
+	assert(0123.01_23 == 123.0123)
+
+	// hexadecimal floats
+	assert(0x0.p+0 == 0.)
+	assert(0Xdeadcafe.p-10 == 0xdeadcafe/1024.0)
+	assert(0x1234.P84 == 0x1234000000000000000000000)
+
+	assert(0x.1p-0 == 1./16)
+	assert(0X.deadcafep4 == 1.0*0xdeadcafe/0x10000000)
+	assert(0x.1234P+12 == 1.0*0x1234/0x10)
+
+	assert(0x0p0 == 0.)
+	assert(0Xdeadcafep+1 == 0x1bd5b95fc)
+	assert(0x1234P-10 == 0x1234/1024.0)
+
+	assert(0x0.0p0 == 0.)
+	assert(0Xdead.cafep+1 == 1.0*0x1bd5b95fc/0x10000)
+	assert(0x12.34P-10 == 1.0*0x1234/0x40000)
+
+	assert(0Xdead_cafep+1 == 0xdeadcafep+1)
+	assert(0x_1234P-10 == 0x1234p-10)
+
+	assert(0X_dead_cafe.p-10 == 0xdeadcafe.p-10)
+	assert(0x12_34.P1_2_3 == 0x1234.p123)
+
+	assert(1_234i == 1234i)
+	assert(1_234_567i == 1234567i)
+
+	assert(0.i == 0i)
+	assert(123.i == 123i)
+	assert(0123.i == 123i)
+
+	assert(0.e+1i == 0i)
+	assert(123.E-1_0i == 123e-10i)
+	assert(01_23.e123i == 123e123i)
+}
diff --git a/src/internal/types/testdata/check/main0.go b/src/internal/types/testdata/check/main0.go
new file mode 100644
index 0000000..132a5fe
--- /dev/null
+++ b/src/internal/types/testdata/check/main0.go
@@ -0,0 +1,9 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main()
+func main /* ERROR "no arguments and no return values" */ /* ERROR redeclared */ (int)
+func main /* ERROR "no arguments and no return values" */ /* ERROR redeclared */ () int
diff --git a/src/internal/types/testdata/check/main1.go b/src/internal/types/testdata/check/main1.go
new file mode 100644
index 0000000..fb567a0
--- /dev/null
+++ b/src/internal/types/testdata/check/main1.go
@@ -0,0 +1,7 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main[T /* ERROR "func main must have no type parameters" */ any]() {}
diff --git a/src/internal/types/testdata/check/map0.go b/src/internal/types/testdata/check/map0.go
new file mode 100644
index 0000000..814d953
--- /dev/null
+++ b/src/internal/types/testdata/check/map0.go
@@ -0,0 +1,113 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package orderedmap provides an ordered map, implemented as a binary tree.
+package orderedmap
+
+// TODO(gri) fix imports for tests
+import "chans" // ERROR could not import
+
+// Map is an ordered map.
+type Map[K, V any] struct {
+	root    *node[K, V]
+	compare func(K, K) int
+}
+
+// node is the type of a node in the binary tree.
+type node[K, V any] struct {
+	key         K
+	val         V
+	left, right *node[K, V]
+}
+
+// New returns a new map.
+func New[K, V any](compare func(K, K) int) *Map[K, V] {
+        return &Map[K, V]{compare: compare}
+}
+
+// find looks up key in the map, and returns either a pointer
+// to the node holding key, or a pointer to the location where
+// such a node would go.
+func (m *Map[K, V]) find(key K) **node[K, V] {
+	pn := &m.root
+	for *pn != nil {
+		switch cmp := m.compare(key, (*pn).key); {
+		case cmp < 0:
+			pn = &(*pn).left
+		case cmp > 0:
+			pn = &(*pn).right
+		default:
+			return pn
+		}
+	}
+	return pn
+}
+
+// Insert inserts a new key/value into the map.
+// If the key is already present, the value is replaced.
+// Returns true if this is a new key, false if already present.
+func (m *Map[K, V]) Insert(key K, val V) bool {
+	pn := m.find(key)
+	if *pn != nil {
+		(*pn).val = val
+		return false
+	}
+        *pn = &node[K, V]{key: key, val: val}
+	return true
+}
+
+// Find returns the value associated with a key, or zero if not present.
+// The found result reports whether the key was found.
+func (m *Map[K, V]) Find(key K) (V, bool) {
+	pn := m.find(key)
+	if *pn == nil {
+		var zero V // see the discussion of zero values, above
+		return zero, false
+	}
+	return (*pn).val, true
+}
+
+// keyValue is a pair of key and value used when iterating.
+type keyValue[K, V any] struct {
+	key K
+	val V
+}
+
+// InOrder returns an iterator that does an in-order traversal of the map.
+func (m *Map[K, V]) InOrder() *Iterator[K, V] {
+	sender, receiver := chans.Ranger[keyValue[K, V]]()
+	var f func(*node[K, V]) bool
+	f = func(n *node[K, V]) bool {
+		if n == nil {
+			return true
+		}
+		// Stop sending values if sender.Send returns false,
+		// meaning that nothing is listening at the receiver end.
+		return f(n.left) &&
+                        sender.Send(keyValue[K, V]{n.key, n.val}) &&
+			f(n.right)
+	}
+	go func() {
+		f(m.root)
+		sender.Close()
+	}()
+	return &Iterator[K, V]{receiver}
+}
+
+// Iterator is used to iterate over the map.
+type Iterator[K, V any] struct {
+	r *chans.Receiver[keyValue[K, V]]
+}
+
+// Next returns the next key and value pair, and a boolean indicating
+// whether they are valid or whether we have reached the end.
+func (it *Iterator[K, V]) Next() (K, V, bool) {
+	keyval, ok := it.r.Next()
+	if !ok {
+		var zerok K
+		var zerov V
+		return zerok, zerov, false
+	}
+	return keyval.key, keyval.val, true
+}
diff --git a/src/internal/types/testdata/check/map1.go b/src/internal/types/testdata/check/map1.go
new file mode 100644
index 0000000..e13bf33
--- /dev/null
+++ b/src/internal/types/testdata/check/map1.go
@@ -0,0 +1,146 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file is like map.go2, but instead if importing chans, it contains
+// the necessary functionality at the end of the file.
+
+// Package orderedmap provides an ordered map, implemented as a binary tree.
+package orderedmap
+
+// Map is an ordered map.
+type Map[K, V any] struct {
+	root    *node[K, V]
+	compare func(K, K) int
+}
+
+// node is the type of a node in the binary tree.
+type node[K, V any] struct {
+	key         K
+	val         V
+	left, right *node[K, V]
+}
+
+// New returns a new map.
+func New[K, V any](compare func(K, K) int) *Map[K, V] {
+        return &Map[K, V]{compare: compare}
+}
+
+// find looks up key in the map, and returns either a pointer
+// to the node holding key, or a pointer to the location where
+// such a node would go.
+func (m *Map[K, V]) find(key K) **node[K, V] {
+	pn := &m.root
+	for *pn != nil {
+		switch cmp := m.compare(key, (*pn).key); {
+		case cmp < 0:
+			pn = &(*pn).left
+		case cmp > 0:
+			pn = &(*pn).right
+		default:
+			return pn
+		}
+	}
+	return pn
+}
+
+// Insert inserts a new key/value into the map.
+// If the key is already present, the value is replaced.
+// Returns true if this is a new key, false if already present.
+func (m *Map[K, V]) Insert(key K, val V) bool {
+	pn := m.find(key)
+	if *pn != nil {
+		(*pn).val = val
+		return false
+	}
+	*pn = &node[K, V]{key: key, val: val}
+	return true
+}
+
+// Find returns the value associated with a key, or zero if not present.
+// The found result reports whether the key was found.
+func (m *Map[K, V]) Find(key K) (V, bool) {
+	pn := m.find(key)
+	if *pn == nil {
+		var zero V // see the discussion of zero values, above
+		return zero, false
+	}
+	return (*pn).val, true
+}
+
+// keyValue is a pair of key and value used when iterating.
+type keyValue[K, V any] struct {
+	key K
+	val V
+}
+
+// InOrder returns an iterator that does an in-order traversal of the map.
+func (m *Map[K, V]) InOrder() *Iterator[K, V] {
+	sender, receiver := chans_Ranger[keyValue[K, V]]()
+	var f func(*node[K, V]) bool
+	f = func(n *node[K, V]) bool {
+		if n == nil {
+			return true
+		}
+		// Stop sending values if sender.Send returns false,
+		// meaning that nothing is listening at the receiver end.
+		return f(n.left) &&
+                        sender.Send(keyValue[K, V]{n.key, n.val}) &&
+			f(n.right)
+	}
+	go func() {
+		f(m.root)
+		sender.Close()
+	}()
+	return &Iterator[K, V]{receiver}
+}
+
+// Iterator is used to iterate over the map.
+type Iterator[K, V any] struct {
+	r *chans_Receiver[keyValue[K, V]]
+}
+
+// Next returns the next key and value pair, and a boolean indicating
+// whether they are valid or whether we have reached the end.
+func (it *Iterator[K, V]) Next() (K, V, bool) {
+	keyval, ok := it.r.Next()
+	if !ok {
+		var zerok K
+		var zerov V
+		return zerok, zerov, false
+	}
+	return keyval.key, keyval.val, true
+}
+
+// chans
+
+func chans_Ranger[T any]() (*chans_Sender[T], *chans_Receiver[T]) { panic(0) }
+
+// A sender is used to send values to a Receiver.
+type chans_Sender[T any] struct {
+	values chan<- T
+	done <-chan bool
+}
+
+func (s *chans_Sender[T]) Send(v T) bool {
+	select {
+	case s.values <- v:
+		return true
+	case <-s.done:
+		return false
+	}
+}
+
+func (s *chans_Sender[T]) Close() {
+	close(s.values)
+}
+
+type chans_Receiver[T any] struct {
+	values <-chan T
+	done chan<- bool
+}
+
+func (r *chans_Receiver[T]) Next() (T, bool) {
+	v, ok := <-r.values
+	return v, ok
+}
diff --git a/src/internal/types/testdata/check/methodsets.go b/src/internal/types/testdata/check/methodsets.go
new file mode 100644
index 0000000..d145bc0
--- /dev/null
+++ b/src/internal/types/testdata/check/methodsets.go
@@ -0,0 +1,214 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package methodsets
+
+type T0 struct {}
+
+func (T0) v0() {}
+func (*T0) p0() {}
+
+type T1 struct {} // like T0 with different method names
+
+func (T1) v1() {}
+func (*T1) p1() {}
+
+type T2 interface {
+	v2()
+	p2()
+}
+
+type T3 struct {
+	T0
+	*T1
+	T2
+}
+
+// Method expressions
+func _() {
+	var (
+		_ func(T0) = T0.v0
+		_ = T0.p0 /* ERROR invalid method expression T0\.p0 \(needs pointer receiver \(\*T0\)\.p0\) */
+
+		_ func (*T0) = (*T0).v0
+		_ func (*T0) = (*T0).p0
+
+		// T1 is like T0
+
+		_ func(T2) = T2.v2
+		_ func(T2) = T2.p2
+
+		_ func(T3) = T3.v0
+		_ func(T3) = T3.p0 /* ERROR invalid method expression T3\.p0 \(needs pointer receiver \(\*T3\)\.p0\) */
+		_ func(T3) = T3.v1
+		_ func(T3) = T3.p1
+		_ func(T3) = T3.v2
+		_ func(T3) = T3.p2
+
+		_ func(*T3) = (*T3).v0
+		_ func(*T3) = (*T3).p0
+		_ func(*T3) = (*T3).v1
+		_ func(*T3) = (*T3).p1
+		_ func(*T3) = (*T3).v2
+		_ func(*T3) = (*T3).p2
+	)
+}
+
+// Method values with addressable receivers
+func _() {
+	var (
+		v0 T0
+		_ func() = v0.v0
+		_ func() = v0.p0
+	)
+
+	var (
+		p0 *T0
+		_ func() = p0.v0
+		_ func() = p0.p0
+	)
+
+	// T1 is like T0
+
+	var (
+		v2 T2
+		_ func() = v2.v2
+		_ func() = v2.p2
+	)
+
+	var (
+		v4 T3
+		_ func() = v4.v0
+		_ func() = v4.p0
+		_ func() = v4.v1
+		_ func() = v4.p1
+		_ func() = v4.v2
+		_ func() = v4.p2
+	)
+
+	var (
+		p4 *T3
+		_ func() = p4.v0
+		_ func() = p4.p0
+		_ func() = p4.v1
+		_ func() = p4.p1
+		_ func() = p4.v2
+		_ func() = p4.p2
+	)
+}
+
+// Method calls with addressable receivers
+func _() {
+	var v0 T0
+	v0.v0()
+	v0.p0()
+
+	var p0 *T0
+	p0.v0()
+	p0.p0()
+
+	// T1 is like T0
+
+	var v2 T2
+	v2.v2()
+	v2.p2()
+
+	var v4 T3
+	v4.v0()
+	v4.p0()
+	v4.v1()
+	v4.p1()
+	v4.v2()
+	v4.p2()
+
+	var p4 *T3
+	p4.v0()
+	p4.p0()
+	p4.v1()
+	p4.p1()
+	p4.v2()
+	p4.p2()
+}
+
+// Method values with value receivers
+func _() {
+	var (
+		_ func() = T0{}.v0
+		_ func() = T0{}.p0 /* ERROR "cannot call pointer method p0 on T0" */
+
+		_ func() = (&T0{}).v0
+		_ func() = (&T0{}).p0
+
+		// T1 is like T0
+
+		// no values for T2
+
+		_ func() = T3{}.v0
+		_ func() = T3{}.p0 /* ERROR "cannot call pointer method p0 on T3" */
+		_ func() = T3{}.v1
+		_ func() = T3{}.p1
+		_ func() = T3{}.v2
+		_ func() = T3{}.p2
+
+		_ func() = (&T3{}).v0
+		_ func() = (&T3{}).p0
+		_ func() = (&T3{}).v1
+		_ func() = (&T3{}).p1
+		_ func() = (&T3{}).v2
+		_ func() = (&T3{}).p2
+	)
+}
+
+// Method calls with value receivers
+func _() {
+	T0{}.v0()
+	T0{}.p0 /* ERROR "cannot call pointer method p0 on T0" */ ()
+
+	(&T0{}).v0()
+	(&T0{}).p0()
+
+	// T1 is like T0
+
+	// no values for T2
+
+	T3{}.v0()
+	T3{}.p0 /* ERROR "cannot call pointer method p0 on T3" */ ()
+	T3{}.v1()
+	T3{}.p1()
+	T3{}.v2()
+	T3{}.p2()
+
+	(&T3{}).v0()
+	(&T3{}).p0()
+	(&T3{}).v1()
+	(&T3{}).p1()
+	(&T3{}).v2()
+	(&T3{}).p2()
+}
+
+// *T has no methods if T is an interface type
+func issue5918() {
+	var (
+		err error
+		_ = err.Error()
+		_ func() string = err.Error
+		_ func(error) string = error.Error
+
+		perr = &err
+		_ = perr.Error /* ERROR "type \*error is pointer to interface, not interface" */ ()
+		_ func() string = perr.Error /* ERROR "type \*error is pointer to interface, not interface" */
+		_ func(*error) string = (*error).Error /* ERROR "type \*error is pointer to interface, not interface" */
+	)
+
+	type T *interface{ m() int }
+	var (
+		x T
+		_ = (*x).m()
+		_ = (*x).m
+
+		_ = x.m /* ERROR "type T is pointer to interface, not interface" */ ()
+		_ = x.m /* ERROR "type T is pointer to interface, not interface" */
+		_ = T.m /* ERROR "type T is pointer to interface, not interface" */
+	)
+}
diff --git a/src/internal/types/testdata/check/shifts.go b/src/internal/types/testdata/check/shifts.go
new file mode 100644
index 0000000..5cd0182
--- /dev/null
+++ b/src/internal/types/testdata/check/shifts.go
@@ -0,0 +1,399 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package shifts
+
+func shifts0() {
+	// basic constant shifts
+	const (
+		s = 10
+		_ = 0<<0
+		_ = 1<<s
+		_ = 1<<- /* ERROR "negative shift count" */ 1
+		// For the test below we may decide to convert to int
+		// rather than uint and then report a negative shift
+		// count instead, which might be a better error. The
+		// (minor) difference is that this would restrict the
+		// shift count range by half (from all uint values to
+		// the positive int values).
+		// This depends on the exact spec wording which is not
+		// done yet.
+		// TODO(gri) revisit and adjust when spec change is done
+		_ = 1<<- /* ERROR "negative shift count" */ 1.0
+		_ = 1<<1075 /* ERROR "invalid shift" */
+		_ = 2.0<<1
+		_ = 1<<1.0
+		_ = 1<<(1+0i)
+
+		_ int = 2<<s
+		_ float32 = 2<<s
+		_ complex64 = 2<<s
+
+		_ int = 2.0<<s
+		_ float32 = 2.0<<s
+		_ complex64 = 2.0<<s
+
+		_ int = 'a'<<s
+		_ float32 = 'a'<<s
+		_ complex64 = 'a'<<s
+	)
+}
+
+func shifts1() {
+	// basic non-constant shifts
+	var (
+		i int
+		u uint
+
+		_ = 1<<0
+		_ = 1<<i
+		_ = 1<<u
+		_ = 1<<"foo" /* ERROR "cannot convert" */
+		_ = i<<0
+		_ = i<<- /* ERROR "negative shift count" */ 1
+		_ = i<<1.0
+		_ = 1<<(1+0i)
+		_ = 1 /* ERROR "overflows" */ <<100
+
+		_ uint = 1 << 0
+		_ uint = 1 << u
+		_ float32 = 1 /* ERROR "must be integer" */ << u
+
+		// issue #14822
+		_ = 1<<( /* ERROR "overflows uint" */ 1<<64)
+		_ = 1<<( /* ERROR "invalid shift count" */ 1<<64-1)
+
+		// issue #43697
+		_ = u<<( /* ERROR "overflows uint" */ 1<<64)
+		_ = u<<(1<<64-1)
+	)
+}
+
+func shifts2() {
+	// from the spec
+	var (
+		s uint = 33
+		i = 1<<s           // 1 has type int
+		j int32 = 1<<s     // 1 has type int32; j == 0
+		k = uint64(1<<s)   // 1 has type uint64; k == 1<<33
+		m int = 1.0<<s     // 1.0 has type int
+		n = 1.0<<s != i    // 1.0 has type int; n == false if ints are 32bits in size
+		o = 1<<s == 2<<s   // 1 and 2 have type int; o == true if ints are 32bits in size
+		p = 1<<s == 1<<33  // illegal if ints are 32bits in size: 1 has type int, but 1<<33 overflows int
+		u = 1.0 /* ERROR "must be integer" */ <<s         // illegal: 1.0 has type float64, cannot shift
+		u1 = 1.0 /* ERROR "must be integer" */ <<s != 0   // illegal: 1.0 has type float64, cannot shift
+		u2 = 1 /* ERROR "must be integer" */ <<s != 1.0   // illegal: 1 has type float64, cannot shift
+		v float32 = 1 /* ERROR "must be integer" */ <<s   // illegal: 1 has type float32, cannot shift
+		w int64 = 1.0<<33  // 1.0<<33 is a constant shift expression
+	)
+	_, _, _, _, _, _, _, _, _, _, _, _ = i, j, k, m, n, o, p, u, u1, u2, v, w
+}
+
+func shifts3(a int16, b float32) {
+	// random tests
+	var (
+		s uint = 11
+		u = 1 /* ERROR "must be integer" */ <<s + 1.0
+		v complex128 = 1 /* ERROR "must be integer" */ << s + 1.0 /* ERROR "must be integer" */ << s + 1
+	)
+	x := 1.0 /* ERROR "must be integer" */ <<s + 1
+	shifts3(1.0 << s, 1 /* ERROR "must be integer" */ >> s)
+	_, _, _ = u, v, x
+}
+
+func shifts4() {
+	// shifts in comparisons w/ untyped operands
+	var s uint
+
+	_ = 1<<s == 1
+	_ = 1 /* ERROR "integer" */ <<s == 1.
+	_ = 1. /* ERROR "integer" */ <<s == 1
+	_ = 1. /* ERROR "integer" */ <<s == 1.
+
+	_ = 1<<s + 1 == 1
+	_ = 1 /* ERROR "integer" */ <<s + 1 == 1.
+	_ = 1 /* ERROR "integer" */ <<s + 1. == 1
+	_ = 1 /* ERROR "integer" */ <<s + 1. == 1.
+	_ = 1. /* ERROR "integer" */ <<s + 1 == 1
+	_ = 1. /* ERROR "integer" */ <<s + 1 == 1.
+	_ = 1. /* ERROR "integer" */ <<s + 1. == 1
+	_ = 1. /* ERROR "integer" */ <<s + 1. == 1.
+
+	_ = 1<<s == 1<<s
+	_ = 1 /* ERROR "integer" */ <<s == 1. /* ERROR "integer" */ <<s
+	_ = 1. /* ERROR "integer" */ <<s == 1 /* ERROR "integer" */ <<s
+	_ = 1. /* ERROR "integer" */ <<s == 1. /* ERROR "integer" */ <<s
+
+	_ = 1<<s + 1<<s == 1
+	_ = 1 /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s == 1.
+	_ = 1 /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s == 1
+	_ = 1 /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s == 1.
+	_ = 1. /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s == 1
+	_ = 1. /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s == 1.
+	_ = 1. /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s == 1
+	_ = 1. /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s == 1.
+
+	_ = 1<<s + 1<<s == 1<<s + 1<<s
+	_ = 1 /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s == 1 /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s
+	_ = 1 /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s == 1. /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s
+	_ = 1 /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s == 1. /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s
+	_ = 1 /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s == 1 /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s
+	_ = 1 /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s == 1 /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s
+	_ = 1 /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s == 1. /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s
+	_ = 1 /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s == 1. /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s
+	_ = 1. /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s == 1 /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s
+	_ = 1. /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s == 1 /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s
+	_ = 1. /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s == 1. /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s
+	_ = 1. /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s == 1. /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s
+	_ = 1. /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s == 1 /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s
+	_ = 1. /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s == 1 /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s
+	_ = 1. /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s == 1. /* ERROR "integer" */ <<s + 1 /* ERROR "integer" */ <<s
+	_ = 1. /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s == 1. /* ERROR "integer" */ <<s + 1. /* ERROR "integer" */ <<s
+}
+
+func shifts5() {
+	// shifts in comparisons w/ typed operands
+	var s uint
+	var x int
+
+	_ = 1<<s == x
+	_ = 1.<<s == x
+	_ = 1.1 /* ERROR "int" */ <<s == x
+
+	_ = 1<<s + x == 1
+	_ = 1<<s + x == 1.
+	_ = 1<<s + x == 1.1 /* ERROR "int" */
+	_ = 1.<<s + x == 1
+	_ = 1.<<s + x == 1.
+	_ = 1.<<s + x == 1.1 /* ERROR "int" */
+	_ = 1.1 /* ERROR "int" */ <<s + x == 1
+	_ = 1.1 /* ERROR "int" */ <<s + x == 1.
+	_ = 1.1 /* ERROR "int" */ <<s + x == 1.1
+
+	_ = 1<<s == x<<s
+	_ = 1.<<s == x<<s
+	_ = 1.1  /* ERROR "int" */ <<s == x<<s
+}
+
+func shifts6() {
+	// shifts as operands in non-arithmetic operations and as arguments
+	var a [10]int
+	var s uint
+
+	_ = a[1<<s]
+	_ = a[1.0]
+	_ = a[1.0<<s]
+
+	_ = make([]int, 1.0)
+	_ = make([]int, 1.0<<s)
+	_ = make([]int, 1.1 /* ERROR "must be integer" */ <<s)
+
+	_ = float32(1)
+	_ = float32(1 /* ERROR "must be integer" */ <<s)
+	_ = float32(1.0)
+	_ = float32(1.0 /* ERROR "must be integer" */ <<s)
+	_ = float32(1.1 /* ERROR "must be integer" */ <<s)
+
+	// TODO(gri) Re-enable these tests once types2 has the go/types fixes.
+	//           Issue #52080.
+	// _ = int32(0x80000000 /* ERROR "overflows int32" */ << s)
+	// TODO(rfindley) Eliminate the redundant error here.
+	// _ = int32(( /* ERROR "truncated to int32" */ 0x80000000 /* ERROR "truncated to int32" */ + 0i) << s)
+
+	_ = int(1+0i<<0)
+	// _ = int((1+0i)<<s)
+	// _ = int(1.0<<s)
+	// _ = int(complex(1, 0)<<s)
+	_ = int(float32/* ERROR "must be integer" */(1.0) <<s)
+	_ = int(1.1 /* ERROR must be integer */ <<s)
+	_ = int(( /* ERROR "must be integer" */ 1+1i)  <<s)
+
+	_ = complex(1 /* ERROR "must be integer" */ <<s, 0)
+
+	var b []int
+	_ = append(b, 1<<s)
+	_ = append(b, 1.0<<s)
+	_ = append(b, (1+0i)<<s)
+	_ = append(b, 1.1 /* ERROR "must be integer" */ <<s)
+	_ = append(b, (1 + 0i) <<s)
+	_ = append(b, ( /* ERROR "must be integer" */ 1 + 1i)  <<s)
+
+	_ = complex(1.0 /* ERROR "must be integer" */ <<s, 0)
+	_ = complex(1.1 /* ERROR "must be integer" */ <<s, 0)
+	_ = complex(0, 1.0 /* ERROR "must be integer" */ <<s)
+	_ = complex(0, 1.1 /* ERROR "must be integer" */ <<s)
+
+	// TODO(gri) The delete below is not type-checked correctly yet.
+	// var m1 map[int]string
+	// delete(m1, 1<<s)
+}
+
+func shifts7() {
+	// shifts of shifts
+	var s uint
+	var x int
+	_ = x
+
+	_ = 1<<(1<<s)
+	_ = 1<<(1.<<s)
+	_ = 1. /* ERROR "integer" */ <<(1<<s)
+	_ = 1. /* ERROR "integer" */ <<(1.<<s)
+
+	x = 1<<(1<<s)
+	x = 1<<(1.<<s)
+	x = 1.<<(1<<s)
+	x = 1.<<(1.<<s)
+
+	_ = (1<<s)<<(1<<s)
+	_ = (1<<s)<<(1.<<s)
+	_ = ( /* ERROR "integer" */ 1.<<s)<<(1<<s)
+	_ = ( /* ERROR "integer" */ 1.<<s)<<(1.<<s)
+
+	x = (1<<s)<<(1<<s)
+	x = (1<<s)<<(1.<<s)
+	x = ( /* ERROR "integer" */ 1.<<s)<<(1<<s)
+	x = ( /* ERROR "integer" */ 1.<<s)<<(1.<<s)
+}
+
+func shifts8() {
+	// shift examples from shift discussion: better error messages
+	var s uint
+	_ = 1.0 /* ERROR "shifted operand 1.0 \(type float64\) must be integer" */ <<s == 1
+	_ = 1.0 /* ERROR "shifted operand 1.0 \(type float64\) must be integer" */ <<s == 1.0
+	_ = 1 /* ERROR "shifted operand 1 \(type float64\) must be integer" */ <<s == 1.0
+	_ = 1 /* ERROR "shifted operand 1 \(type float64\) must be integer" */ <<s + 1.0 == 1
+	_ = 1 /* ERROR "shifted operand 1 \(type float64\) must be integer" */ <<s + 1.1 == 1
+	_ = 1 /* ERROR "shifted operand 1 \(type float64\) must be integer" */ <<s + 1 == 1.0
+
+	// additional cases
+	_ = complex(1.0 /* ERROR "shifted operand 1.0 \(type float64\) must be integer" */ <<s, 1)
+	_ = complex(1.0, 1 /* ERROR "shifted operand 1 \(type float64\) must be integer" */ <<s)
+
+	_ = int(1.<<s)
+	_ = int(1.1 /* ERROR "shifted operand .* must be integer" */ <<s)
+	_ = float32(1 /* ERROR "shifted operand .* must be integer" */ <<s)
+	_ = float32(1. /* ERROR "shifted operand .* must be integer" */ <<s)
+	_ = float32(1.1 /* ERROR "shifted operand .* must be integer" */ <<s)
+	// TODO(gri) the error messages for these two are incorrect - disabled for now
+	// _ = complex64(1<<s)
+	// _ = complex64(1.<<s)
+	_ = complex64(1.1 /* ERROR "shifted operand .* must be integer" */ <<s)
+}
+
+func shifts9() {
+	// various originally failing snippets of code from the std library
+	// from src/compress/lzw/reader.go:90
+	{
+		var d struct {
+			bits     uint32
+			width    uint
+		}
+		_ = uint16(d.bits & (1<<d.width - 1))
+	}
+
+	// from src/debug/dwarf/buf.go:116
+	{
+		var ux uint64
+		var bits uint
+		x := int64(ux)
+		if x&(1<<(bits-1)) != 0 {}
+	}
+
+	// from src/encoding/asn1/asn1.go:160
+	{
+		var bytes []byte
+		if bytes[len(bytes)-1]&((1<<bytes[0])-1) != 0 {}
+	}
+
+	// from src/math/big/rat.go:140
+	{
+		var exp int
+		var mantissa uint64
+		shift := uint64(-1022 - (exp - 1)) // [1..53)
+		_ = mantissa & (1<<shift - 1)
+	}
+
+	// from src/net/interface.go:51
+	{
+		type Flags uint
+		var f Flags
+		var i int
+		if f&(1<<uint(i)) != 0 {}
+	}
+
+	// from src/runtime/softfloat64.go:234
+	{
+		var gm uint64
+		var shift uint
+		_ = gm & (1<<shift - 1)
+	}
+
+	// from src/strconv/atof.go:326
+	{
+		var mant uint64
+		var mantbits uint
+		if mant == 2<<mantbits {}
+	}
+
+	// from src/route_bsd.go:82
+	{
+		var Addrs int32
+		const rtaRtMask = 1
+		var i uint
+		if Addrs&rtaRtMask&(1<<i) == 0 {}
+	}
+
+	// from src/text/scanner/scanner.go:540
+	{
+		var s struct { Whitespace uint64 }
+		var ch rune
+		for s.Whitespace&(1<<uint(ch)) != 0 {}
+	}
+}
+
+func issue5895() {
+	var x = 'a' << 1 // type of x must be rune
+	var _ rune = x
+}
+
+func issue11325() {
+	var _ = 0 >> 1.1 /* ERROR "truncated to uint" */ // example from issue 11325
+	_ = 0 >> 1.1 /* ERROR "truncated to uint" */
+	_ = 0 << 1.1 /* ERROR "truncated to uint" */
+	_ = 0 >> 1.
+	_ = 1 >> 1.1 /* ERROR "truncated to uint" */
+	_ = 1 >> 1.
+	_ = 1. >> 1
+	_ = 1. >> 1.
+	_ = 1.1 /* ERROR "must be integer" */ >> 1
+}
+
+func issue11594() {
+	var _ = complex64 /* ERROR "must be integer" */ (1) << 2 // example from issue 11594
+	_ = float32 /* ERROR "must be integer" */ (0) << 1
+	_ = float64 /* ERROR "must be integer" */ (0) >> 2
+	_ = complex64 /* ERROR "must be integer" */ (0) << 3
+	_ = complex64 /* ERROR "must be integer" */ (0) >> 4
+}
+
+func issue21727() {
+	var s uint
+	var a = make([]int, 1<<s + 1.2 /* ERROR "truncated to int" */ )
+	var _ = a[1<<s - 2.3 /* ERROR "truncated to int" */ ]
+	var _ int = 1<<s + 3.4 /* ERROR "truncated to int" */
+	var _ = string(1 /* ERROR shifted operand 1 .* must be integer */ << s)
+	var _ = string(1.0 /* ERROR "cannot convert" */ << s)
+}
+
+func issue22969() {
+	var s uint
+	var a []byte
+	_ = a[0xffffffffffffffff /* ERROR "overflows int" */ <<s] // example from issue 22969
+	_ = make([]int, 0xffffffffffffffff /* ERROR "overflows int" */ << s)
+	_ = make([]int, 0, 0xffffffffffffffff /* ERROR "overflows int" */ << s)
+	var _ byte = 0x100 /* ERROR "overflows byte" */ << s
+	var _ int8 = 0xff /* ERROR "overflows int8" */ << s
+	var _ int16 = 0xffff /* ERROR "overflows int16" */ << s
+	var _ int32 = 0x80000000 /* ERROR "overflows int32" */ << s
+}
diff --git a/src/internal/types/testdata/check/slices.go b/src/internal/types/testdata/check/slices.go
new file mode 100644
index 0000000..2bacd1c
--- /dev/null
+++ b/src/internal/types/testdata/check/slices.go
@@ -0,0 +1,68 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package slices implements various slice algorithms.
+package slices
+
+// Map turns a []T1 to a []T2 using a mapping function.
+func Map[T1, T2 any](s []T1, f func(T1) T2) []T2 {
+	r := make([]T2, len(s))
+	for i, v := range s {
+		r[i] = f(v)
+	}
+	return r
+}
+
+// Reduce reduces a []T1 to a single value using a reduction function.
+func Reduce[T1, T2 any](s []T1, initializer T2, f func(T2, T1) T2) T2 {
+	r := initializer
+	for _, v := range s {
+		r = f(r, v)
+	}
+	return r
+}
+
+// Filter filters values from a slice using a filter function.
+func Filter[T any](s []T, f func(T) bool) []T {
+	var r []T
+	for _, v := range s {
+		if f(v) {
+			r = append(r, v)
+		}
+	}
+	return r
+}
+
+// Example uses
+
+func limiter(x int) byte {
+	switch {
+	case x < 0:
+		return 0
+	default:
+		return byte(x)
+	case x > 255:
+		return 255
+	}
+}
+
+var input = []int{-4, 68954, 7, 44, 0, -555, 6945}
+var limited1 = Map[int, byte](input, limiter)
+var limited2 = Map(input, limiter) // using type inference
+
+func reducer(x float64, y int) float64 {
+	return x + float64(y)
+}
+
+var reduced1 = Reduce[int, float64](input, 0, reducer)
+var reduced2 = Reduce(input, 1i /* ERROR overflows */, reducer) // using type inference
+var reduced3 = Reduce(input, 1, reducer) // using type inference
+
+func filter(x int) bool {
+	return x&1 != 0
+}
+
+var filtered1 = Filter[int](input, filter)
+var filtered2 = Filter(input, filter) // using type inference
+
diff --git a/src/internal/types/testdata/check/stmt0.go b/src/internal/types/testdata/check/stmt0.go
new file mode 100644
index 0000000..c456aac
--- /dev/null
+++ b/src/internal/types/testdata/check/stmt0.go
@@ -0,0 +1,994 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// statements
+
+package stmt0
+
+func assignments0() (int, int) {
+	var a, b, c int
+	var ch chan int
+	f0 := func() {}
+	f1 := func() int { return 1 }
+	f2 := func() (int, int) { return 1, 2 }
+	f3 := func() (int, int, int) { return 1, 2, 3 }
+
+	a, b, c = 1, 2, 3
+	a, b, c = 1 /* ERROR "assignment mismatch: 3 variables but 2 values" */ , 2
+	a, b, c = 1 /* ERROR "assignment mismatch: 3 variables but 4 values" */ , 2, 3, 4
+	_, _, _ = a, b, c
+
+	a = f0 /* ERROR "used as value" */ ()
+	a = f1()
+	a = f2 /* ERROR "assignment mismatch: 1 variable but f2 returns 2 values" */ ()
+	a, b = f2()
+	a, b, c = f2 /* ERROR "assignment mismatch: 3 variables but f2 returns 2 values" */ ()
+	a, b, c = f3()
+	a, b = f3 /* ERROR "assignment mismatch: 2 variables but f3 returns 3 values" */ ()
+
+	a, b, c = <- /* ERROR "assignment mismatch: 3 variables but 1 value" */ ch
+
+	return /* ERROR "not enough return values\n\thave \(\)\n\twant \(int, int\)" */
+	return 1 /* ERROR "not enough return values\n\thave \(number\)\n\twant \(int, int\)" */
+	return 1, 2
+	return 1, 2, 3 /* ERROR "too many return values\n\thave \(number, number, number\)\n\twant \(int, int\)" */
+}
+
+func assignments1() {
+	b, i, f, c, s := false, 1, 1.0, 1i, "foo"
+	b = i /* ERROR "cannot use .* in assignment" */
+	i = f /* ERROR "cannot use .* in assignment" */
+	f = c /* ERROR "cannot use .* in assignment" */
+	c = s /* ERROR "cannot use .* in assignment" */
+	s = b /* ERROR "cannot use .* in assignment" */
+
+	v0, v1, v2 := 1 /* ERROR "assignment mismatch" */ , 2, 3, 4
+	_, _, _ = v0, v1, v2
+
+	b = true
+
+	i += 1
+	i /* ERROR "mismatched types int and untyped string" */+= "foo"
+
+	f -= 1
+	f /= 0
+	f = float32(0)/0 /* ERROR "division by zero" */
+	f /* ERROR "mismatched types float64 and untyped string" */-= "foo"
+
+	c *= 1
+	c /= 0
+
+	s += "bar"
+	s /* ERROR "mismatched types string and untyped int" */+= 1
+
+	var u64 uint64
+	u64 += 1<<u64
+
+	undefined /* ERROR "undefined" */ = 991
+
+	// test cases for issue 5800
+	var (
+		_ int = nil /* ERROR "cannot use nil as int value in variable declaration" */
+		_ [10]int = nil /* ERROR "cannot use nil as \[10\]int value in variable declaration" */
+		_ []byte = nil
+		_ struct{} = nil /* ERROR "cannot use nil as struct{} value in variable declaration" */
+		_ func() = nil
+		_ map[int]string = nil
+		_ chan int = nil
+	)
+
+	// test cases for issue 5500
+	_ = func() (int, bool) {
+		var m map[int]int
+		return m /* ERROR "not enough return values" */ [0]
+	}
+
+	g := func(int, bool){}
+	var m map[int]int
+	g(m[0]) /* ERROR "not enough arguments" */
+
+	// assignments to _
+	_ = nil /* ERROR "use of untyped nil" */
+	_ = 1  << /* ERROR constant shift overflow */ 1000
+	(_) = 0
+}
+
+func assignments2() {
+	type mybool bool
+	var m map[string][]bool
+	var s []bool
+	var b bool
+	var d mybool
+	_ = s
+	_ = b
+	_ = d
+
+	// assignments to map index expressions are ok
+	s, b = m["foo"]
+	_, d = m["bar"]
+	m["foo"] = nil
+	m["foo"] = nil /* ERROR assignment mismatch: 1 variable but 2 values */ , false
+	_ = append(m["foo"])
+	_ = append(m["foo"], true)
+
+	var c chan int
+	_, b = <-c
+	_, d = <-c
+	<- /* ERROR cannot assign */ c = 0
+	<-c = 0 /* ERROR assignment mismatch: 1 variable but 2 values */ , false
+
+	var x interface{}
+	_, b = x.(int)
+	x /* ERROR cannot assign */ .(int) = 0
+	x.(int) = 0 /* ERROR assignment mismatch: 1 variable but 2 values */ , false
+
+	assignments2 /* ERROR used as value */ () = nil
+	int /* ERROR not an expression */ = 0
+}
+
+func issue6487() {
+	type S struct{x int}
+	_ = &S /* ERROR "cannot take address" */ {}.x
+	_ = &( /* ERROR "cannot take address" */ S{}.x)
+	_ = (&S{}).x
+	S /* ERROR "cannot assign" */ {}.x = 0
+	(&S{}).x = 0
+
+	type M map[string]S
+	var m M
+	m /* ERROR "cannot assign to struct field" */ ["foo"].x = 0
+	_ = &( /* ERROR "cannot take address" */ m["foo"].x)
+	_ = &m /* ERROR "cannot take address" */ ["foo"].x
+}
+
+func issue6766a() {
+	a, a /* ERROR a repeated on left side of := */ := 1, 2
+	_ = a
+	a, b, b /* ERROR b repeated on left side of := */ := 1, 2, 3
+	_ = b
+	c, c /* ERROR c repeated on left side of := */, b := 1, 2, 3
+	_ = c
+	a, b := /* ERROR no new variables */ 1, 2
+}
+
+func shortVarDecls1() {
+	const c = 0
+	type d int
+	a, b, c /* ERROR "cannot assign" */ , d /* ERROR "cannot assign" */  := 1, "zwei", 3.0, 4
+	var _ int = a // a is of type int
+	var _ string = b // b is of type string
+}
+
+func incdecs() {
+	const c = 3.14
+	c /* ERROR "cannot assign" */ ++
+	s := "foo"
+	s /* ERROR "invalid operation" */ --
+	3.14 /* ERROR "cannot assign" */ ++
+	var (
+		x int
+		y float32
+		z complex128
+	)
+	x++
+	y--
+	z++
+}
+
+func sends() {
+	var ch chan int
+	var rch <-chan int
+	var x int
+	x <- /* ERROR "cannot send" */ x
+	rch <- /* ERROR "cannot send" */ x
+	ch <- "foo" /* ERROR "cannot use .* in send" */
+	ch <- x
+}
+
+func selects() {
+	select {}
+	var (
+		ch chan int
+		sc chan <- bool
+	)
+	select {
+	case <-ch:
+	case (<-ch):
+	case t := <-ch:
+		_ = t
+	case t := (<-ch):
+		_ = t
+	case t, ok := <-ch:
+		_, _ = t, ok
+	case t, ok := (<-ch):
+		_, _ = t, ok
+	case <-sc /* ERROR "cannot receive from send-only channel" */ :
+	}
+	select {
+	default:
+	default /* ERROR "multiple defaults" */ :
+	}
+	select {
+	case a, b := <-ch:
+		_, b = a, b
+	case x /* ERROR send or receive */ :
+	case a /* ERROR send or receive */ := ch:
+	}
+
+	// test for issue 9570: ch2 in second case falsely resolved to
+	// ch2 declared in body of first case
+	ch1 := make(chan int)
+	ch2 := make(chan int)
+	select {
+	case <-ch1:
+		var ch2 /* ERROR ch2 declared and not used */ chan bool
+	case i := <-ch2:
+		print(i + 1)
+	}
+}
+
+func gos() {
+	go 1; /* ERROR "must be function call" */
+	go int /* ERROR "go requires function call, not conversion" */ (0)
+	go ( /* ERROR expression in go must not be parenthesized */ gos())
+	go gos()
+	var c chan int
+	go close(c)
+	go len /* ERROR "go discards result" */ (c)
+}
+
+func defers() {
+	defer 1; /* ERROR "must be function call" */
+	defer int /* ERROR "defer requires function call, not conversion" */ (0)
+	defer ( /* ERROR expression in defer must not be parenthesized */ defers())
+	defer defers()
+	var c chan int
+	defer close(c)
+	defer len /* ERROR "defer discards result" */ (c)
+}
+
+func breaks() {
+	var x, y int
+
+	break /* ERROR "break" */
+	{
+		break /* ERROR "break" */
+	}
+	if x < y {
+		break /* ERROR "break" */
+	}
+
+	switch x {
+	case 0:
+		break
+	case 1:
+		if x == y {
+			break
+		}
+	default:
+		break
+		break
+	}
+
+	var z interface{}
+	switch z.(type) {
+	case int:
+		break
+	}
+
+	for {
+		break
+	}
+
+	var a []int
+	for _ = range a {
+		break
+	}
+
+	for {
+		if x == y {
+			break
+		}
+	}
+
+	var ch chan int
+	select {
+	case <-ch:
+		break
+	}
+
+	select {
+	case <-ch:
+		if x == y {
+			break
+		}
+	default:
+		break
+	}
+}
+
+func continues() {
+	var x, y int
+
+	continue /* ERROR "continue" */
+	{
+		continue /* ERROR "continue" */
+	}
+
+	if x < y {
+		continue /* ERROR "continue" */
+	}
+
+	switch x {
+	case 0:
+		continue /* ERROR "continue" */
+	}
+
+	var z interface{}
+	switch z.(type) {
+	case int:
+		continue /* ERROR "continue" */
+	}
+
+	var ch chan int
+	select {
+	case <-ch:
+		continue /* ERROR "continue" */
+	}
+
+	for i := 0; i < 10; i++ {
+		continue
+		if x < y {
+			continue
+			break
+		}
+		switch x {
+		case y:
+			continue
+		default:
+			break
+		}
+		select {
+		case <-ch:
+			continue
+		}
+	}
+
+	var a []int
+	for _ = range a {
+		continue
+		if x < y {
+			continue
+			break
+		}
+		switch x {
+		case y:
+			continue
+		default:
+			break
+		}
+		select {
+		case <-ch:
+			continue
+		}
+	}
+}
+
+func returns0() {
+	return
+	return 0 /* ERROR too many return values */
+}
+
+func returns1(x float64) (int, *float64) {
+	return 0, &x
+	return /* ERROR not enough return values */
+	return "foo" /* ERROR "cannot .* in return statement" */, x /* ERROR "cannot use .* in return statement" */
+	return 0, &x, 1 /* ERROR too many return values */
+}
+
+func returns2() (a, b int) {
+	return
+	return 1, "foo" /* ERROR cannot use .* in return statement */
+	return 1, 2, 3 /* ERROR too many return values */
+	{
+		type a int
+		return 1, 2
+		return /* ERROR a not in scope at return */
+	}
+}
+
+func returns3() (_ int) {
+	return
+	{
+		var _ int // blank (_) identifiers never shadow since they are in no scope
+		return
+	}
+}
+
+func switches0() {
+	var x int
+
+	switch x {
+	}
+
+	switch x {
+	default:
+	default /* ERROR "multiple defaults" */ :
+	}
+
+	switch {
+	case 1  /* ERROR "cannot convert" */ :
+	}
+
+	true := "false"
+	_ = true
+	// A tagless switch is equivalent to the bool
+        // constant true, not the identifier 'true'.
+	switch {
+	case "false" /* ERROR "cannot convert" */:
+	}
+
+	switch int32(x) {
+	case 1, 2:
+	case x /* ERROR "invalid case x in switch on int32\(x\) \(mismatched types int and int32\)" */ :
+	}
+
+	switch x {
+	case 1 /* ERROR "overflows" */ << 100:
+	}
+
+	switch x {
+	case 1:
+	case 1 /* ERROR "duplicate case" */ :
+	case ( /* ERROR "duplicate case" */ 1):
+	case 2, 3, 4:
+	case 5, 1 /* ERROR "duplicate case" */ :
+	}
+
+	switch uint64(x) {
+	case 1<<64 - 1:
+	case 1 /* ERROR duplicate case */ <<64 - 1:
+	case 2, 3, 4:
+	case 5, 1 /* ERROR duplicate case */ <<64 - 1:
+	}
+
+	var y32 float32
+	switch y32 {
+	case 1.1:
+	case 11/10: // integer division!
+	case 11. /* ERROR duplicate case */ /10:
+	case 2, 3.0, 4.1:
+	case 5.2, 1.10 /* ERROR duplicate case */ :
+	}
+
+	var y64 float64
+	switch y64 {
+	case 1.1:
+	case 11/10: // integer division!
+	case 11. /* ERROR duplicate case */ /10:
+	case 2, 3.0, 4.1:
+	case 5.2, 1.10 /* ERROR duplicate case */ :
+	}
+
+	var s string
+	switch s {
+	case "foo":
+	case "foo" /* ERROR duplicate case */ :
+	case "f" /* ERROR duplicate case */ + "oo":
+	case "abc", "def", "ghi":
+	case "jkl", "foo" /* ERROR duplicate case */ :
+	}
+
+	type T int
+	type F float64
+	type S string
+	type B bool
+	var i interface{}
+	switch i {
+	case nil:
+	case nil: // no duplicate detection
+	case (*int)(nil):
+	case (*int)(nil): // do duplicate detection
+	case 1:
+	case byte(1):
+	case int /* ERROR duplicate case */ (1):
+	case T(1):
+	case 1.0:
+	case F(1.0):
+	case F /* ERROR duplicate case */ (1.0):
+	case "hello":
+	case S("hello"):
+	case S /* ERROR duplicate case */ ("hello"):
+	case 1==1, B(false):
+	case false, B(2==2):
+	}
+
+	// switch on array
+	var a [3]int
+	switch a {
+	case [3]int{1, 2, 3}:
+	case [3]int{1, 2, 3}: // no duplicate detection
+	case [ /* ERROR "mismatched types */ 4]int{4, 5, 6}:
+	}
+
+	// switch on channel
+	var c1, c2 chan int
+	switch c1 {
+	case nil:
+	case c1:
+	case c2:
+	case c1, c2: // no duplicate detection
+	}
+}
+
+func switches1() {
+	fallthrough /* ERROR "fallthrough statement out of place" */
+
+	var x int
+	switch x {
+	case 0:
+		fallthrough /* ERROR "fallthrough statement out of place" */
+		break
+	case 1:
+		fallthrough
+	case 2:
+		fallthrough; ; ; // trailing empty statements are ok
+	case 3:
+	default:
+		fallthrough; ;
+	case 4:
+		fallthrough /* ERROR "cannot fallthrough final case in switch" */
+	}
+
+	var y interface{}
+	switch y.(type) {
+	case int:
+		fallthrough /* ERROR "cannot fallthrough in type switch" */ ; ; ;
+	default:
+	}
+
+	switch x {
+	case 0:
+		if x == 0 {
+			fallthrough /* ERROR "fallthrough statement out of place" */
+		}
+	}
+
+	switch x {
+	case 0:
+		goto L1
+		L1: fallthrough; ;
+	case 1:
+		goto L2
+		goto L3
+		goto L4
+		L2: L3: L4: fallthrough
+	default:
+	}
+
+	switch x {
+	case 0:
+		goto L5
+		L5: fallthrough
+	default:
+		goto L6
+		goto L7
+		goto L8
+		L6: L7: L8: fallthrough /* ERROR "cannot fallthrough final case in switch" */
+	}
+
+	switch x {
+	case 0:
+		fallthrough; ;
+	case 1:
+		{
+			fallthrough /* ERROR "fallthrough statement out of place" */
+		}
+	case 2:
+		fallthrough
+	case 3:
+		fallthrough /* ERROR "fallthrough statement out of place" */
+		{ /* empty block is not an empty statement */ }; ;
+	default:
+		fallthrough /* ERROR "cannot fallthrough final case in switch" */
+	}
+
+	switch x {
+	case 0:
+		{
+			fallthrough /* ERROR "fallthrough statement out of place" */
+		}
+	}
+}
+
+func switches2() {
+	// untyped nil is not permitted as switch expression
+	switch nil /* ERROR "use of untyped nil" */ {
+	case 1, 2, "foo": // don't report additional errors here
+	}
+
+	// untyped constants are converted to default types
+	switch 1<<63-1 {
+	}
+	switch 1 /* ERROR "cannot use .* as int value.*\(overflows\)" */ << 63 {
+	}
+	var x int
+	switch 1.0 {
+	case 1.0, 2.0, x /* ERROR "mismatched types int and float64" */ :
+	}
+	switch x {
+	case 1.0:
+	}
+
+	// untyped bools become of type bool
+	type B bool
+	var b B = true
+	switch x == x {
+	case b /* ERROR "mismatched types B and bool" */ :
+	}
+	switch {
+	case b /* ERROR "mismatched types B and bool" */ :
+	}
+}
+
+func issue11667() {
+	switch 9223372036854775808 /* ERROR "cannot use .* as int value.*\(overflows\)" */ {
+	}
+	switch 9223372036854775808 /* ERROR "cannot use .* as int value.*\(overflows\)" */ {
+	case 9223372036854775808:
+	}
+	var x int
+	switch x {
+	case 9223372036854775808 /* ERROR "overflows int" */ :
+	}
+	var y float64
+	switch y {
+	case 9223372036854775808:
+	}
+}
+
+func issue11687() {
+	f := func() (_, _ int) { return }
+	switch f /* ERROR "multiple-value f" */ () {
+	}
+	var x int
+	switch f /* ERROR "multiple-value f" */ () {
+	case x:
+	}
+	switch x {
+	case f /* ERROR "multiple-value f" */ ():
+	}
+}
+
+type I interface {
+	m()
+}
+
+type I2 interface {
+	m(int)
+}
+
+type T struct{}
+type T1 struct{}
+type T2 struct{}
+
+func (T) m() {}
+func (T2) m(int) {}
+
+func typeswitches() {
+	var i int
+	var x interface{}
+
+	switch x.(type) {}
+	switch (x /* ERROR "outside type switch" */ .(type)) {}
+
+	switch x.(type) {
+	default:
+	default /* ERROR "multiple defaults" */ :
+	}
+
+	switch x /* ERROR "declared and not used" */ := x.(type) {}
+	switch _ /* ERROR "no new variable on left side of :=" */ := x.(type) {}
+
+	switch x := x.(type) {
+	case int:
+		var y int = x
+		_ = y
+	}
+
+	switch x /* ERROR "x declared and not used" */ := i /* ERROR "not an interface" */ .(type) {}
+
+	switch t := x.(type) {
+	case nil:
+		var v bool = t /* ERROR "cannot use .* in variable declaration" */
+		_ = v
+	case int:
+		var v int = t
+		_ = v
+	case float32, complex64:
+		var v float32 = t /* ERROR "cannot use .* in variable declaration" */
+		_ = v
+	default:
+		var v float32 = t /* ERROR "cannot use .* in variable declaration" */
+		_ = v
+	}
+
+	var t I
+	switch t.(type) {
+	case T:
+	case T1 /* ERROR "missing method m" */ :
+	case T2 /* ERROR "wrong type for method m" */ :
+	case I2 /* STRICT "wrong type for method m" */ : // only an error in strict mode (issue 8561)
+	}
+
+
+	{
+		x := 1
+		v := 2
+		switch v /* ERROR "v [(]variable of type int[)] is not an interface" */ .(type) {
+		case int:
+			println(x)
+			println(x / 0 /* ERROR "invalid operation: division by zero" */)
+		case 1 /* ERROR "1 is not a type" */:
+		}
+	}
+}
+
+// Test that each case clause uses the correct type of the variable
+// declared by the type switch (issue 5504).
+func typeswitch0() {
+	switch y := interface{}(nil).(type) {
+	case int:
+		func() int { return y + 0 }()
+	case float32:
+		func() float32 { return y }()
+	}
+}
+
+// Test correct scope setup.
+// (no redeclaration errors expected in the type switch)
+func typeswitch1() {
+	var t I
+	switch t := t; t := t.(type) {
+	case nil:
+		var _ I = t
+	case T:
+		var _ T = t
+	default:
+		var _ I = t
+	}
+}
+
+// Test correct typeswitch against interface types.
+type A interface { a() }
+type B interface { b() }
+type C interface { a(int) }
+
+func typeswitch2() {
+	switch A(nil).(type) {
+	case A:
+	case B:
+	case C /* STRICT "cannot have dynamic type" */: // only an error in strict mode (issue 8561)
+	}
+}
+
+func typeswitch3(x interface{}) {
+	switch x.(type) {
+	case int:
+	case float64:
+	case int /* ERROR duplicate case */ :
+	}
+
+	switch x.(type) {
+	case nil:
+	case int:
+	case nil /* ERROR duplicate case */ , nil /* ERROR duplicate case */ :
+	}
+
+	type F func(int)
+	switch x.(type) {
+	case nil:
+	case int, func(int):
+	case float32, func /* ERROR duplicate case */ (x int):
+	case F:
+	}
+}
+
+func fors1() {
+	for {}
+	var i string
+	_ = i
+	for i := 0; i < 10; i++ {}
+	for i := 0; i < 10; j /* ERROR cannot declare */ := 0 {}
+}
+
+func rangeloops1() {
+	var (
+		x int
+		a [10]float32
+		b []string
+		p *[10]complex128
+		pp **[10]complex128
+		s string
+		m map[int]bool
+		c chan int
+		sc chan<- int
+		rc <-chan int
+	)
+
+	for range x /* ERROR "cannot range over" */ {}
+	for _ = range x /* ERROR "cannot range over" */ {}
+	for i := range x /* ERROR "cannot range over" */ {}
+
+	for range a {}
+	for i := range a {
+		var ii int
+		ii = i
+		_ = ii
+	}
+	for i, x := range a {
+		var ii int
+		ii = i
+		_ = ii
+		var xx float64
+		xx = x /* ERROR "cannot use .* in assignment" */
+		_ = xx
+	}
+	var ii int
+	var xx float32
+	for ii, xx = range a {}
+	_, _ = ii, xx
+
+	for range b {}
+	for i := range b {
+		var ii int
+		ii = i
+		_ = ii
+	}
+	for i, x := range b {
+		var ii int
+		ii = i
+		_ = ii
+		var xx string
+		xx = x
+		_ = xx
+	}
+
+	for range s {}
+	for i := range s {
+		var ii int
+		ii = i
+		_ = ii
+	}
+	for i, x := range s {
+		var ii int
+		ii = i
+		_ = ii
+		var xx rune
+		xx = x
+		_ = xx
+	}
+
+	for range p {}
+	for _, x := range p {
+		var xx complex128
+		xx = x
+		_ = xx
+	}
+
+	for range pp /* ERROR "cannot range over" */ {}
+	for _, x := range pp /* ERROR "cannot range over" */ {}
+
+	for range m {}
+	for k := range m {
+		var kk int32
+		kk = k /* ERROR "cannot use .* in assignment" */
+		_ = kk
+	}
+	for k, v := range m {
+		var kk int
+		kk = k
+		_ = kk
+		if v {}
+	}
+
+	for range c {}
+	for _, _ /* ERROR "only one iteration variable" */ = range c {}
+	for e := range c {
+		var ee int
+		ee = e
+		_ = ee
+	}
+	for _ = range sc /* ERROR "cannot range over" */ {}
+	for _ = range rc {}
+
+	// constant strings
+	const cs = "foo"
+	for range cs {}
+	for range "" {}
+	for i, x := range cs { _, _ = i, x }
+	for i, x := range "" {
+		var ii int
+		ii = i
+		_ = ii
+		var xx rune
+		xx = x
+		_ = xx
+	}
+}
+
+func rangeloops2() {
+	type I int
+	type R rune
+
+	var a [10]int
+	var i I
+	_ = i
+	for i /* ERROR cannot use .* in assignment */ = range a {}
+	for i /* ERROR cannot use .* in assignment */ = range &a {}
+	for i /* ERROR cannot use .* in assignment */ = range a[:] {}
+
+	var s string
+	var r R
+	_ = r
+	for i /* ERROR cannot use .* in assignment */ = range s {}
+	for i /* ERROR cannot use .* in assignment */ = range "foo" {}
+	for _, r /* ERROR cannot use .* in assignment */ = range s {}
+	for _, r /* ERROR cannot use .* in assignment */ = range "foo" {}
+}
+
+func issue6766b() {
+	for _ := /* ERROR no new variables */ range "" {}
+	for a, a /* ERROR redeclared */ := range "" { _ = a }
+	var a int
+	_ = a
+	for a, a /* ERROR redeclared */ := range []int{1, 2, 3} { _ = a }
+}
+
+// Test that despite errors in the range clause,
+// the loop body is still type-checked (and thus
+// errors reported).
+func issue10148() {
+	for y /* ERROR declared and not used */ := range "" {
+		_ = "" /* ERROR mismatched types untyped string and untyped int */ + 1
+	}
+	for range 1 /* ERROR cannot range over 1 */ {
+		_ = "" /* ERROR mismatched types untyped string and untyped int */ + 1
+	}
+	for y := range 1 /* ERROR cannot range over 1 */ {
+		_ = "" /* ERROR mismatched types untyped string and untyped int */ + 1
+	}
+}
+
+func labels0() {
+	goto L0
+	goto L1
+	L0:
+	L1:
+	L1 /* ERROR "already declared" */ :
+	if true {
+		goto L2
+		L2:
+		L0 /* ERROR "already declared" */ :
+	}
+	_ = func() {
+		goto L0
+		goto L1
+		goto L2
+		L0:
+		L1:
+		L2:
+	}
+}
+
+func expression_statements(ch chan int) {
+	expression_statements(ch)
+	<-ch
+	println()
+
+	0 /* ERROR "not used" */
+	1 /* ERROR "not used" */ +2
+	cap /* ERROR "not used" */ (ch)
+	println /* ERROR "must be called" */
+}
diff --git a/src/internal/types/testdata/check/stmt1.go b/src/internal/types/testdata/check/stmt1.go
new file mode 100644
index 0000000..f79f920
--- /dev/null
+++ b/src/internal/types/testdata/check/stmt1.go
@@ -0,0 +1,259 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// terminating statements
+
+package stmt1
+
+func _() {}
+
+func _() int {} /* ERROR "missing return" */
+
+func _() int { panic(0) }
+func _() int { (panic(0)) }
+
+// block statements
+func _(x, y int) (z int) {
+	{
+		return
+	}
+}
+
+func _(x, y int) (z int) {
+	{
+		return; ; ; // trailing empty statements are ok
+	}
+	; ; ;
+}
+
+func _(x, y int) (z int) {
+	{
+	}
+} /* ERROR "missing return" */
+
+func _(x, y int) (z int) {
+	{
+		; ; ;
+	}
+	; ; ;
+} /* ERROR "missing return" */
+
+// if statements
+func _(x, y int) (z int) {
+	if x < y { return }
+	return 1
+}
+
+func _(x, y int) (z int) {
+	if x < y { return; ; ; ; }
+	return 1
+}
+
+func _(x, y int) (z int) {
+	if x < y { return }
+	return 1; ;
+}
+
+func _(x, y int) (z int) {
+	if x < y { return }
+} /* ERROR "missing return" */
+
+func _(x, y int) (z int) {
+	if x < y {
+	} else { return 1
+	}
+} /* ERROR "missing return" */
+
+func _(x, y int) (z int) {
+	if x < y { return
+	} else { return
+	}
+}
+
+// for statements
+func _(x, y int) (z int) {
+	for x < y {
+		return
+	}
+} /* ERROR "missing return" */
+
+func _(x, y int) (z int) {
+	for {
+		return
+	}
+}
+
+func _(x, y int) (z int) {
+	for {
+		return; ; ; ;
+	}
+}
+
+func _(x, y int) (z int) {
+	for {
+		return
+		break
+	}
+	; ; ;
+} /* ERROR "missing return" */
+
+func _(x, y int) (z int) {
+	for {
+		for { break }
+		return
+	}
+}
+
+func _(x, y int) (z int) {
+	for {
+		for { break }
+		return ; ;
+	}
+	;
+}
+
+func _(x, y int) (z int) {
+L:	for {
+		for { break L }
+		return
+	}
+} /* ERROR "missing return" */
+
+// switch statements
+func _(x, y int) (z int) {
+	switch x {
+	case 0: return
+	default: return
+	}
+}
+
+func _(x, y int) (z int) {
+	switch x {
+	case 0: return;
+	default: return; ; ;
+	}
+}
+
+func _(x, y int) (z int) {
+	switch x {
+	case 0: return
+	}
+} /* ERROR "missing return" */
+
+func _(x, y int) (z int) {
+	switch x {
+	case 0: return
+	case 1: break
+	}
+} /* ERROR "missing return" */
+
+func _(x, y int) (z int) {
+	switch x {
+	case 0: return
+	default:
+		switch y {
+		case 0: break
+		}
+		panic(0)
+	}
+}
+
+func _(x, y int) (z int) {
+	switch x {
+	case 0: return
+	default:
+		switch y {
+		case 0: break
+		}
+		panic(0); ; ;
+	}
+	;
+}
+
+func _(x, y int) (z int) {
+L:	switch x {
+	case 0: return
+	default:
+		switch y {
+		case 0: break L
+		}
+		panic(0)
+	}
+} /* ERROR "missing return" */
+
+// select statements
+func _(ch chan int) (z int) {
+	select {}
+} // nice!
+
+func _(ch chan int) (z int) {
+	select {}
+	; ;
+}
+
+func _(ch chan int) (z int) {
+	select {
+	default: break
+	}
+} /* ERROR "missing return" */
+
+func _(ch chan int) (z int) {
+	select {
+	case <-ch: return
+	default: break
+	}
+} /* ERROR "missing return" */
+
+func _(ch chan int) (z int) {
+	select {
+	case <-ch: return
+	default:
+		for i := 0; i < 10; i++ {
+			break
+		}
+		return
+	}
+}
+
+func _(ch chan int) (z int) {
+	select {
+	case <-ch: return; ; ;
+	default:
+		for i := 0; i < 10; i++ {
+			break
+		}
+		return; ; ;
+	}
+	; ; ;
+}
+
+func _(ch chan int) (z int) {
+L:	select {
+	case <-ch: return
+	default:
+		for i := 0; i < 10; i++ {
+			break L
+		}
+		return
+	}
+	; ; ;
+} /* ERROR "missing return" */
+
+func parenPanic() int {
+	((((((panic)))(0))))
+}
+
+func issue23218a() int {
+	{
+		panic := func(interface{}){}
+		panic(0)
+	}
+} /* ERROR "missing return" */
+
+func issue23218b() int {
+	{
+		panic := func(interface{}){}
+		((((panic))))(0)
+	}
+} /* ERROR "missing return" */
diff --git a/src/internal/types/testdata/check/typeinference.go b/src/internal/types/testdata/check/typeinference.go
new file mode 100644
index 0000000..28f3e28
--- /dev/null
+++ b/src/internal/types/testdata/check/typeinference.go
@@ -0,0 +1,49 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package typeInference
+
+// As of issue #51527, type-type inference has been disabled.
+
+// basic inference
+type Tb[P ~*Q, Q any] int
+func _() {
+	var x Tb /* ERROR got 1 arguments */ [*int]
+	var y Tb[*int, int]
+	x = y /* ERROR cannot use y .* in assignment */
+	_ = x
+}
+
+// recursive inference
+type Tr[A any, B *C, C *D, D *A] int
+func _() {
+	var x Tr /* ERROR got 1 arguments */ [string]
+	var y Tr[string, ***string, **string, *string]
+	var z Tr[int, ***int, **int, *int]
+	x = y /* ERROR cannot use y .* in assignment */
+	x = z // ERROR cannot use z .* as Tr
+	_ = x
+}
+
+// other patterns of inference
+type To0[A any, B []A] int
+type To1[A any, B struct{a A}] int
+type To2[A any, B [][]A] int
+type To3[A any, B [3]*A] int
+type To4[A any, B any, C struct{a A; b B}] int
+func _() {
+	var _ To0 /* ERROR got 1 arguments */ [int]
+	var _ To1 /* ERROR got 1 arguments */ [int]
+	var _ To2 /* ERROR got 1 arguments */ [int]
+	var _ To3 /* ERROR got 1 arguments */ [int]
+	var _ To4 /* ERROR got 2 arguments */ [int, string]
+}
+
+// failed inference
+type Tf0[A, B any] int
+type Tf1[A any, B ~struct{a A; c C}, C any] int
+func _() {
+	var _ Tf0 /* ERROR got 1 arguments but 2 type parameters */ [int]
+	var _ Tf1 /* ERROR got 1 arguments but 3 type parameters */ [int]
+}
diff --git a/src/internal/types/testdata/check/typeinst0.go b/src/internal/types/testdata/check/typeinst0.go
new file mode 100644
index 0000000..c21cb53
--- /dev/null
+++ b/src/internal/types/testdata/check/typeinst0.go
@@ -0,0 +1,62 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type myInt int
+
+// Parameterized type declarations
+
+// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
+type T1[P any] P // ERROR cannot use a type parameter as RHS in type declaration
+
+type T2[P any] struct {
+        f P
+        g int // int should still be in scope chain
+}
+
+type List[P any] []P
+
+// Alias type declarations cannot have type parameters.
+// Issue #46477 proposses to change that.
+type A1[P any] = /* ERROR cannot be alias */ struct{}
+
+// Pending clarification of #46477 we disallow aliases
+// of generic types.
+type A2 = List // ERROR cannot use generic type
+var _ A2[int]
+var _ A2
+
+type A3 = List[int]
+var _ A3
+
+// Parameterized type instantiations
+
+var x int
+type _ x /* ERROR not a type */ [int]
+
+type _ int /* ERROR not a generic type */ [] // ERROR expected type argument list
+type _ myInt /* ERROR not a generic type */ [] // ERROR expected type argument list
+
+// TODO(gri) better error messages
+type _ T1[] // ERROR expected type argument list
+type _ T1[x /* ERROR not a type */ ]
+type _ T1 /* ERROR got 2 arguments but 1 type parameters */ [int, float32]
+
+var _ T2[int] = T2[int]{}
+
+var _ List[int] = []int{1, 2, 3}
+var _ List[[]int] = [][]int{{1, 2, 3}}
+var _ List[List[List[int]]]
+
+// Parameterized types containing parameterized types
+
+type T3[P any] List[P]
+
+var _ T3[int] = T3[int](List[int]{1, 2, 3})
+
+// Self-recursive generic types are not permitted
+
+type self1[P any] self1 /* ERROR invalid recursive type */ [P]
+type self2[P any] *self2[P] // this is ok
diff --git a/src/internal/types/testdata/check/typeinst1.go b/src/internal/types/testdata/check/typeinst1.go
new file mode 100644
index 0000000..e7bb247
--- /dev/null
+++ b/src/internal/types/testdata/check/typeinst1.go
@@ -0,0 +1,282 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type List[E any] []E
+var _ List[List[List[int]]]
+var _ List[List[List[int]]] = []List[List[int]]{}
+
+type (
+	T1[P1 any] struct {
+		f1 T2[P1, float32]
+	}
+
+	T2[P2, P3 any] struct {
+		f2 P2
+		f3 P3
+	}
+)
+
+func _() {
+	var x1 T1[int]
+	var x2 T2[int, float32]
+
+	x1.f1.f2 = 0
+	x1.f1 = x2
+}
+
+type T3[P any] T1[T2[P, P]]
+
+func _() {
+	var x1 T3[int]
+	var x2 T2[int, int]
+	x1.f1.f2 = x2
+}
+
+func f[P any] (x P) List[P] {
+	return List[P]{x}
+}
+
+var (
+	_ []int = f(0)
+	_ []float32 = f[float32](10)
+	_ List[complex128] = f(1i)
+	_ []List[int] = f(List[int]{})
+        _ List[List[int]] = []List[int]{}
+        _ = []List[int]{}
+)
+
+// Parameterized types with methods
+
+func (l List[E]) Head() (_ E, _ bool) {
+	if len(l) > 0 {
+		return l[0], true
+	}
+	return
+}
+
+// A test case for instantiating types with other types (extracted from map.go2)
+
+type Pair[K any] struct {
+	key K
+}
+
+type Receiver[T any] struct {
+	values T
+}
+
+type Iterator[K any] struct {
+	r Receiver[Pair[K]]
+}
+
+func Values [T any] (r Receiver[T]) T {
+        return r.values
+}
+
+func (it Iterator[K]) Next() K {
+        return Values[Pair[K]](it.r).key
+}
+
+// A more complex test case testing type bounds (extracted from linalg.go2 and reduced to essence)
+
+type NumericAbs[T any] interface {
+	Abs() T
+}
+
+func AbsDifference[T NumericAbs[T]](x T) { panic(0) }
+
+// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
+// type OrderedAbs[T any] T
+// 
+// func (a OrderedAbs[T]) Abs() OrderedAbs[T]
+// 
+// func OrderedAbsDifference[T any](x T) {
+// 	AbsDifference(OrderedAbs[T](x))
+// }
+
+// same code, reduced to essence
+
+func g[P interface{ m() P }](x P) { panic(0) }
+
+// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
+// type T4[P any] P
+// 
+// func (_ T4[P]) m() T4[P]
+// 
+// func _[Q any](x Q) {
+// 	g(T4[Q](x))
+// }
+
+// Another test case that caused  problems in the past
+
+type T5[_ interface { a() }, _ interface{}] struct{}
+
+type A[P any] struct{ x P }
+
+func (_ A[P]) a() {}
+
+var _ T5[A[int], int]
+
+// Invoking methods with parameterized receiver types uses
+// type inference to determine the actual type arguments matching
+// the receiver type parameters from the actual receiver argument.
+// Go does implicit address-taking and dereferenciation depending
+// on the actual receiver and the method's receiver type. To make
+// type inference work, the type-checker matches "pointer-ness"
+// of the actual receiver and the method's receiver type.
+// The following code tests this mechanism.
+
+type R1[A any] struct{}
+func (_ R1[A]) vm()
+func (_ *R1[A]) pm()
+
+func _[T any](r R1[T], p *R1[T]) {
+	r.vm()
+	r.pm()
+	p.vm()
+	p.pm()
+}
+
+type R2[A, B any] struct{}
+func (_ R2[A, B]) vm()
+func (_ *R2[A, B]) pm()
+
+func _[T any](r R2[T, int], p *R2[string, T]) {
+	r.vm()
+	r.pm()
+	p.vm()
+	p.pm()
+}
+
+// It is ok to have multiple embedded unions.
+type _ interface {
+	m0()
+	~int | ~string | ~bool
+	~float32 | ~float64
+	m1()
+	m2()
+	~complex64 | ~complex128
+	~rune
+}
+
+// Type sets may contain each type at most once.
+type _ interface {
+	~int|~ /* ERROR overlapping terms ~int */ int
+	~int|int /* ERROR overlapping terms int */
+	int|int /* ERROR overlapping terms int */
+}
+
+type _ interface {
+	~struct{f int} | ~struct{g int} | ~ /* ERROR overlapping terms */ struct{f int}
+}
+
+// Interface term lists can contain any type, incl. *Named types.
+// Verify that we use the underlying type(s) of the type(s) in the
+// term list when determining if an operation is permitted.
+
+type MyInt int
+func add1[T interface{MyInt}](x T) T {
+	return x + 1
+}
+
+type MyString string
+func double[T interface{MyInt|MyString}](x T) T {
+	return x + x
+}
+
+// Embedding of interfaces with term lists leads to interfaces
+// with term lists that are the intersection of the embedded
+// term lists.
+
+type E0 interface {
+	~int | ~bool | ~string
+}
+
+type E1 interface {
+	~int | ~float64 | ~string
+}
+
+type E2 interface {
+	~float64
+}
+
+type I0 interface {
+	E0
+}
+
+func f0[T I0]() {}
+var _ = f0[int]
+var _ = f0[bool]
+var _ = f0[string]
+var _ = f0[float64 /* ERROR does not satisfy I0 */ ]
+
+type I01 interface {
+	E0
+	E1
+}
+
+func f01[T I01]() {}
+var _ = f01[int]
+var _ = f01[bool /* ERROR does not satisfy I0 */ ]
+var _ = f01[string]
+var _ = f01[float64 /* ERROR does not satisfy I0 */ ]
+
+type I012 interface {
+	E0
+	E1
+	E2
+}
+
+func f012[T I012]() {}
+var _ = f012[int /* ERROR cannot satisfy I012.*empty type set */ ]
+var _ = f012[bool /* ERROR cannot satisfy I012.*empty type set */ ]
+var _ = f012[string /* ERROR cannot satisfy I012.*empty type set */ ]
+var _ = f012[float64 /* ERROR cannot satisfy I012.*empty type set */ ]
+
+type I12 interface {
+	E1
+	E2
+}
+
+func f12[T I12]() {}
+var _ = f12[int /* ERROR does not satisfy I12 */ ]
+var _ = f12[bool /* ERROR does not satisfy I12 */ ]
+var _ = f12[string /* ERROR does not satisfy I12 */ ]
+var _ = f12[float64]
+
+type I0_ interface {
+	E0
+	~int
+}
+
+func f0_[T I0_]() {}
+var _ = f0_[int]
+var _ = f0_[bool /* ERROR does not satisfy I0_ */ ]
+var _ = f0_[string /* ERROR does not satisfy I0_ */ ]
+var _ = f0_[float64 /* ERROR does not satisfy I0_ */ ]
+
+// Using a function instance as a type is an error.
+var _ f0 // ERROR not a type
+var _ f0 /* ERROR not a type */ [int]
+
+// Empty type sets can only be satisfied by empty type sets.
+type none interface {
+	// force an empty type set
+        int
+        string
+}
+
+func ff[T none]() {}
+func gg[T any]() {}
+func hh[T ~int]() {}
+
+func _[T none]() {
+	_ = ff[int /* ERROR cannot satisfy none \(empty type set\) */ ]
+	_ = ff[T]  // pathological but ok because T's type set is empty, too
+	_ = gg[int]
+	_ = gg[T]
+	_ = hh[int]
+	_ = hh[T]
+}
diff --git a/src/internal/types/testdata/check/typeinstcycles.go b/src/internal/types/testdata/check/typeinstcycles.go
new file mode 100644
index 0000000..74fe191
--- /dev/null
+++ b/src/internal/types/testdata/check/typeinstcycles.go
@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "unsafe"
+
+func F1[T any](_ [unsafe.Sizeof(F1[int])]T) (res T)      { return }
+func F2[T any](_ T) (res [unsafe.Sizeof(F2[string])]int) { return }
+func F3[T any](_ [unsafe.Sizeof(F1[string])]int)         {}
diff --git a/src/internal/types/testdata/check/typeparams.go b/src/internal/types/testdata/check/typeparams.go
new file mode 100644
index 0000000..0e440d8
--- /dev/null
+++ b/src/internal/types/testdata/check/typeparams.go
@@ -0,0 +1,508 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// import "io" // for type assertion tests
+
+var _ any // ok to use any anywhere
+func _[_ any, _ interface{any}](any) {
+        var _ any
+}
+
+func identity[T any](x T) T { return x }
+
+func _[_ any](x int) int { panic(0) }
+func _[T any](T /* ERROR redeclared */ T)() {}
+func _[T, T /* ERROR redeclared */ any]() {}
+
+// Constraints (incl. any) may be parenthesized.
+func _[_ (any)]() {}
+func _[_ (interface{})]() {}
+
+func reverse[T any](list []T) []T {
+        rlist := make([]T, len(list))
+        i := len(list)
+        for _, x := range list {
+                i--
+                rlist[i] = x
+        }
+        return rlist
+}
+
+var _ = reverse /* ERROR cannot use generic function reverse */
+var _ = reverse[int, float32 /* ERROR got 2 type arguments */ ] ([]int{1, 2, 3})
+var _ = reverse[int]([ /* ERROR cannot use */ ]float32{1, 2, 3})
+var f = reverse[chan int]
+var _ = f(0 /* ERROR cannot use 0 .* as \[\]chan int */ )
+
+func swap[A, B any](a A, b B) (B, A) { return b, a }
+
+var _ = swap /* ERROR multiple-value */ [int, float32](1, 2)
+var f32, i = swap[int, float32](swap[float32, int](1, 2))
+var _ float32 = f32
+var _ int = i
+
+func swapswap[A, B any](a A, b B) (A, B) {
+        return swap[B, A](b, a)
+}
+
+type F[A, B any] func(A, B) (B, A)
+
+func min[T interface{ ~int }](x, y T) T {
+        if x < y {
+                return x
+        }
+        return y
+}
+
+func _[T interface{~int | ~float32}](x, y T) bool { return x < y }
+func _[T any](x, y T) bool { return x /* ERROR type parameter T is not comparable */ < y }
+func _[T interface{~int | ~float32 | ~bool}](x, y T) bool { return x /* ERROR type parameter T is not comparable */ < y }
+
+func _[T C1[T]](x, y T) bool { return x /* ERROR type parameter T is not comparable */ < y }
+func _[T C2[T]](x, y T) bool { return x < y }
+
+type C1[T any] interface{}
+type C2[T any] interface{ ~int | ~float32 }
+
+func new[T any]() *T {
+        var x T
+        return &x
+}
+
+var _ = new /* ERROR cannot use generic function new */
+var _ *int = new[int]()
+
+func _[T any](map[T /* ERROR invalid map key type T \(missing comparable constraint\) */]int) {} // w/o constraint we don't know if T is comparable
+
+func f1[T1 any](struct{T1 /* ERROR cannot be a .* type parameter */ }) int { panic(0) }
+var _ = f1[int](struct{T1}{})
+type T1 = int
+
+func f2[t1 any](struct{t1 /* ERROR cannot be a .* type parameter */ ; x float32}) int { panic(0) }
+var _ = f2[t1](struct{t1; x float32}{})
+type t1 = int
+
+
+func f3[A, B, C any](A, struct{x B}, func(A, struct{x B}, *C)) int { panic(0) }
+
+var _ = f3[int, rune, bool](1, struct{x rune}{}, nil)
+
+// indexing
+
+func _[T any] (x T, i int) { _ = x /* ERROR "cannot index" */ [i] }
+func _[T interface{ ~int }] (x T, i int) { _ = x /* ERROR "cannot index" */ [i] }
+func _[T interface{ ~string }] (x T, i int) { _ = x[i] }
+func _[T interface{ ~[]int }] (x T, i int) { _ = x[i] }
+func _[T interface{ ~[10]int | ~*[20]int | ~map[int]int }] (x T, i int) { _ = x /* ERROR cannot index */ [i] } // map and non-map types
+func _[T interface{ ~string | ~[]byte }] (x T, i int) { _ = x[i] }
+func _[T interface{ ~[]int | ~[1]rune }] (x T, i int) { _ = x /* ERROR "cannot index" */ [i] }
+func _[T interface{ ~string | ~[]rune }] (x T, i int) { _ = x /* ERROR "cannot index" */ [i] }
+
+// indexing with various combinations of map types in type sets (see issue #42616)
+func _[T interface{ ~[]E | ~map[int]E }, E any](x T, i int) { _ = x /* ERROR cannot index */ [i] } // map and non-map types
+func _[T interface{ ~[]E }, E any](x T, i int) { _ = &x[i] }
+func _[T interface{ ~map[int]E }, E any](x T, i int) { _, _ = x[i] } // comma-ok permitted
+func _[T interface{ ~map[int]E }, E any](x T, i int) { _ = &x /* ERROR cannot take address */ [i] }
+func _[T interface{ ~map[int]E | ~map[uint]E }, E any](x T, i int) { _ = x /* ERROR cannot index */ [i] } // different map element types
+func _[T interface{ ~[]E | ~map[string]E }, E any](x T, i int) { _ = x /* ERROR cannot index */ [i] } // map and non-map types
+
+// indexing with various combinations of array and other types in type sets
+func _[T interface{ [10]int }](x T, i int) { _ = x[i]; _ = x[9]; _ = x[10 /* ERROR out of bounds */ ] }
+func _[T interface{ [10]byte | string }](x T, i int) { _ = x[i]; _ = x[9]; _ = x[10 /* ERROR out of bounds */ ] }
+func _[T interface{ [10]int | *[20]int | []int }](x T, i int) { _ = x[i]; _ = x[9]; _ = x[10 /* ERROR out of bounds */ ] }
+
+// indexing with strings and non-variable arrays (assignment not permitted)
+func _[T string](x T) { _ = x[0]; x /* ERROR cannot assign */ [0] = 0 }
+func _[T []byte | string](x T) { x /* ERROR cannot assign */ [0] = 0 }
+func _[T [10]byte]() { f := func() (x T) { return }; f /* ERROR cannot assign */ ()[0] = 0 }
+func _[T [10]byte]() { f := func() (x *T) { return }; f /* ERROR cannot index */ ()[0] = 0 }
+func _[T [10]byte]() { f := func() (x *T) { return }; (*f())[0] = 0 }
+func _[T *[10]byte]() { f := func() (x T) { return }; f()[0] = 0 }
+
+// slicing
+
+func _[T interface{ ~[10]E }, E any] (x T, i, j, k int) { var _ []E = x[i:j] }
+func _[T interface{ ~[10]E }, E any] (x T, i, j, k int) { var _ []E = x[i:j:k] }
+func _[T interface{ ~[]byte }] (x T, i, j, k int) { var _ T = x[i:j] }
+func _[T interface{ ~[]byte }] (x T, i, j, k int) { var _ T = x[i:j:k] }
+func _[T interface{ ~string }] (x T, i, j, k int) { var _ T = x[i:j] }
+func _[T interface{ ~string }] (x T, i, j, k int) { var _ T = x[i:j:k /* ERROR 3-index slice of string */ ] }
+
+type myByte1 []byte
+type myByte2 []byte
+func _[T interface{ []byte | myByte1 | myByte2 }] (x T, i, j, k int) { var _ T = x[i:j:k] }
+func _[T interface{ []byte | myByte1 | []int }] (x T, i, j, k int) { var _ T = x /* ERROR no core type */ [i:j:k] }
+
+func _[T interface{ []byte | myByte1 | myByte2 | string }] (x T, i, j, k int) { var _ T = x[i:j] }
+func _[T interface{ []byte | myByte1 | myByte2 | string }] (x T, i, j, k int) { var _ T = x[i:j:k /* ERROR 3-index slice of string */ ] }
+func _[T interface{ []byte | myByte1 | []int | string }] (x T, i, j, k int) { var _ T = x /* ERROR no core type */ [i:j] }
+
+// len/cap built-ins
+
+func _[T any](x T) { _ = len(x /* ERROR invalid argument */ ) }
+func _[T interface{ ~int }](x T) { _ = len(x /* ERROR invalid argument */ ) }
+func _[T interface{ ~string | ~[]byte | ~int }](x T) { _ = len(x /* ERROR invalid argument */ ) }
+func _[T interface{ ~string }](x T) { _ = len(x) }
+func _[T interface{ ~[10]int }](x T) { _ = len(x) }
+func _[T interface{ ~[]byte }](x T) { _ = len(x) }
+func _[T interface{ ~map[int]int }](x T) { _ = len(x) }
+func _[T interface{ ~chan int }](x T) { _ = len(x) }
+func _[T interface{ ~string | ~[]byte | ~chan int }](x T) { _ = len(x) }
+
+func _[T any](x T) { _ = cap(x /* ERROR invalid argument */ ) }
+func _[T interface{ ~int }](x T) { _ = cap(x /* ERROR invalid argument */ ) }
+func _[T interface{ ~string | ~[]byte | ~int }](x T) { _ = cap(x /* ERROR invalid argument */ ) }
+func _[T interface{ ~string }](x T) { _ = cap(x /* ERROR invalid argument */ ) }
+func _[T interface{ ~[10]int }](x T) { _ = cap(x) }
+func _[T interface{ ~[]byte }](x T) { _ = cap(x) }
+func _[T interface{ ~map[int]int }](x T) { _ = cap(x /* ERROR invalid argument */ ) }
+func _[T interface{ ~chan int }](x T) { _ = cap(x) }
+func _[T interface{ ~[]byte | ~chan int }](x T) { _ = cap(x) }
+
+// range iteration
+
+func _[T interface{}](x T) {
+        for range x /* ERROR cannot range */ {}
+}
+
+type myString string
+
+func _[
+        B1 interface{ string },
+        B2 interface{ string | myString },
+
+        C1 interface{ chan int },
+        C2 interface{ chan int | <-chan int },
+        C3 interface{ chan<- int },
+
+        S1 interface{ []int },
+        S2 interface{ []int | [10]int },
+
+        A1 interface{ [10]int },
+        A2 interface{ [10]int | []int },
+
+        P1 interface{ *[10]int },
+        P2 interface{ *[10]int | *[]int },
+
+        M1 interface{ map[string]int },
+        M2 interface{ map[string]int | map[string]string },
+]() {
+        var b0 string
+        for range b0 {}
+        for _ = range b0 {}
+        for _, _ = range b0 {}
+
+        var b1 B1
+        for range b1 {}
+        for _ = range b1 {}
+        for _, _ = range b1 {}
+
+        var b2 B2
+        for range b2 {}
+
+        var c0 chan int
+        for range c0 {}
+        for _ = range c0 {}
+        for _, _ /* ERROR permits only one iteration variable */ = range c0 {}
+
+        var c1 C1
+        for range c1 {}
+        for _ = range c1 {}
+        for _, _ /* ERROR permits only one iteration variable */ = range c1 {}
+
+        var c2 C2
+        for range c2 {}
+
+        var c3 C3
+        for range c3 /* ERROR receive from send-only channel */ {}
+
+        var s0 []int
+        for range s0 {}
+        for _ = range s0 {}
+        for _, _ = range s0 {}
+
+        var s1 S1
+        for range s1 {}
+        for _ = range s1 {}
+        for _, _ = range s1 {}
+
+        var s2 S2
+        for range s2 /* ERROR cannot range over s2.*no core type */ {}
+
+        var a0 []int
+        for range a0 {}
+        for _ = range a0 {}
+        for _, _ = range a0 {}
+
+        var a1 A1
+        for range a1 {}
+        for _ = range a1 {}
+        for _, _ = range a1 {}
+
+        var a2 A2
+        for range a2 /* ERROR cannot range over a2.*no core type */ {}
+
+        var p0 *[10]int
+        for range p0 {}
+        for _ = range p0 {}
+        for _, _ = range p0 {}
+
+        var p1 P1
+        for range p1 {}
+        for _ = range p1 {}
+        for _, _ = range p1 {}
+
+        var p2 P2
+        for range p2 /* ERROR cannot range over p2.*no core type */ {}
+
+        var m0 map[string]int
+        for range m0 {}
+        for _ = range m0 {}
+        for _, _ = range m0 {}
+
+        var m1 M1
+        for range m1 {}
+        for _ = range m1 {}
+        for _, _ = range m1 {}
+
+        var m2 M2
+        for range m2 /* ERROR cannot range over m2.*no core type */ {}
+}
+
+// type inference checks
+
+var _ = new /* ERROR cannot infer T */ ()
+
+func f4[A, B, C any](A, B) C { panic(0) }
+
+var _ = f4 /* ERROR cannot infer C */ (1, 2)
+var _ = f4[int, float32, complex128](1, 2)
+
+func f5[A, B, C any](A, []*B, struct{f []C}) int { panic(0) }
+
+var _ = f5[int, float32, complex128](0, nil, struct{f []complex128}{})
+var _ = f5 /* ERROR cannot infer */ (0, nil, struct{f []complex128}{})
+var _ = f5(0, []*float32{new[float32]()}, struct{f []complex128}{})
+
+func f6[A any](A, []A) int { panic(0) }
+
+var _ = f6(0, nil)
+
+func f6nil[A any](A) int { panic(0) }
+
+var _ = f6nil /* ERROR cannot infer */ (nil)
+
+// type inference with variadic functions
+
+func f7[T any](...T) T { panic(0) }
+
+var _ int = f7 /* ERROR cannot infer T */ ()
+var _ int = f7(1)
+var _ int = f7(1, 2)
+var _ int = f7([]int{}...)
+var _ int = f7 /* ERROR cannot use */ ([]float64{}...)
+var _ float64 = f7([]float64{}...)
+var _ = f7[float64](1, 2.3)
+var _ = f7(float64(1), 2.3)
+var _ = f7(1, 2.3 /* ERROR does not match */ )
+var _ = f7(1.2, 3 /* ERROR does not match */ )
+
+func f8[A, B any](A, B, ...B) int { panic(0) }
+
+var _ = f8(1) /* ERROR not enough arguments */
+var _ = f8(1, 2.3)
+var _ = f8(1, 2.3, 3.4, 4.5)
+var _ = f8(1, 2.3, 3.4, 4 /* ERROR does not match */ )
+var _ = f8[int, float64](1, 2.3, 3.4, 4)
+
+var _ = f8[int, float64](0, 0, nil...) // test case for #18268
+
+// init functions cannot have type parameters
+
+func init() {}
+func init[_ /* ERROR func init must have no type parameters */ any]() {}
+func init[P /* ERROR func init must have no type parameters */ any]() {}
+
+type T struct {}
+
+func (T) m1() {}
+func (T) m2[ /* ERROR method must have no type parameters */ _ any]() {}
+func (T) m3[ /* ERROR method must have no type parameters */ P any]() {}
+
+// type inference across parameterized types
+
+type S1[P any] struct { f P }
+
+func f9[P any](x S1[P]) {}
+
+func _() {
+        f9[int](S1[int]{42})
+	f9(S1[int]{42})
+}
+
+type S2[A, B, C any] struct{}
+
+func f10[X, Y, Z any](a S2[X, int, Z], b S2[X, Y, bool]) {}
+
+func _[P any]() {
+        f10[int, float32, string](S2[int, int, string]{}, S2[int, float32, bool]{})
+        f10(S2[int, int, string]{}, S2[int, float32, bool]{})
+        f10(S2[P, int, P]{}, S2[P, float32, bool]{})
+}
+
+// corner case for type inference
+// (was bug: after instanting f11, the type-checker didn't mark f11 as non-generic)
+
+func f11[T any]() {}
+
+func _() {
+	f11[int]()
+}
+
+// the previous example was extracted from
+
+// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
+// func f12[T interface{m() T}]() {}
+// 
+// type A[T any] T
+// 
+// func (a A[T]) m() A[T]
+// 
+// func _[T any]() {
+// 	f12[A[T]]()
+// }
+
+// method expressions
+
+func (_ S1[P]) m()
+
+func _() {
+	m := S1[int].m
+	m(struct { f int }{42})
+}
+
+func _[T any] (x T) {
+        m := S1[T].m
+        m(S1[T]{x})
+}
+
+type I1[A any] interface {
+        m1(A)
+}
+
+var _ I1[int] = r1[int]{}
+
+type r1[T any] struct{}
+
+func (_ r1[T]) m1(T)
+
+type I2[A, B any] interface {
+        m1(A)
+        m2(A) B
+}
+
+var _ I2[int, float32] = R2[int, float32]{}
+
+type R2[P, Q any] struct{}
+
+func (_ R2[X, Y]) m1(X)
+func (_ R2[X, Y]) m2(X) Y
+
+// type assertions and type switches over generic types
+// NOTE: These are currently disabled because it's unclear what the correct
+// approach is, and one can always work around by assigning the variable to
+// an interface first.
+
+// // ReadByte1 corresponds to the ReadByte example in the draft design.
+// func ReadByte1[T io.Reader](r T) (byte, error) {
+// 	if br, ok := r.(io.ByteReader); ok {
+// 		return br.ReadByte()
+// 	}
+// 	var b [1]byte
+// 	_, err := r.Read(b[:])
+// 	return b[0], err
+// }
+//
+// // ReadBytes2 is like ReadByte1 but uses a type switch instead.
+// func ReadByte2[T io.Reader](r T) (byte, error) {
+//         switch br := r.(type) {
+//         case io.ByteReader:
+//                 return br.ReadByte()
+//         }
+// 	var b [1]byte
+// 	_, err := r.Read(b[:])
+// 	return b[0], err
+// }
+//
+// // type assertions and type switches over generic types are strict
+// type I3 interface {
+//         m(int)
+// }
+//
+// type I4 interface {
+//         m() int // different signature from I3.m
+// }
+//
+// func _[T I3](x I3, p T) {
+//         // type assertions and type switches over interfaces are not strict
+//         _ = x.(I4)
+//         switch x.(type) {
+//         case I4:
+//         }
+//
+//         // type assertions and type switches over generic types are strict
+//         _ = p /* ERROR cannot have dynamic type I4 */.(I4)
+//         switch p.(type) {
+//         case I4 /* ERROR cannot have dynamic type I4 */ :
+//         }
+// }
+
+// type assertions and type switches over generic types lead to errors for now
+
+func _[T any](x T) {
+	_ = x /* ERROR cannot use type assertion */ .(int)
+	switch x /* ERROR cannot use type switch */ .(type) {
+	}
+
+	// work-around
+	var t interface{} = x
+	_ = t.(int)
+	switch t.(type) {
+	}
+}
+
+func _[T interface{~int}](x T) {
+	_ = x /* ERROR cannot use type assertion */ .(int)
+	switch x /* ERROR cannot use type switch */ .(type) {
+	}
+
+	// work-around
+	var t interface{} = x
+	_ = t.(int)
+	switch t.(type) {
+	}
+}
+
+// error messages related to type bounds mention those bounds
+type C[P any] interface{}
+
+func _[P C[P]] (x P) {
+	x.m /* ERROR x.m undefined */ ()
+}
+
+type I interface {}
+
+func _[P I] (x P) {
+	x.m /* ERROR type P has no field or method m */ ()
+}
+
+func _[P interface{}] (x P) {
+	x.m /* ERROR type P has no field or method m */ ()
+}
+
+func _[P any] (x P) {
+	x.m /* ERROR type P has no field or method m */ ()
+}
diff --git a/src/internal/types/testdata/check/unions.go b/src/internal/types/testdata/check/unions.go
new file mode 100644
index 0000000..bcd7de6
--- /dev/null
+++ b/src/internal/types/testdata/check/unions.go
@@ -0,0 +1,66 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check that overlong unions don't bog down type checking.
+// Disallow them for now.
+
+package p
+
+type t int
+
+type (
+	t00 t; t01 t; t02 t; t03 t; t04 t; t05 t; t06 t; t07 t; t08 t; t09 t
+	t10 t; t11 t; t12 t; t13 t; t14 t; t15 t; t16 t; t17 t; t18 t; t19 t
+	t20 t; t21 t; t22 t; t23 t; t24 t; t25 t; t26 t; t27 t; t28 t; t29 t
+	t30 t; t31 t; t32 t; t33 t; t34 t; t35 t; t36 t; t37 t; t38 t; t39 t
+	t40 t; t41 t; t42 t; t43 t; t44 t; t45 t; t46 t; t47 t; t48 t; t49 t
+	t50 t; t51 t; t52 t; t53 t; t54 t; t55 t; t56 t; t57 t; t58 t; t59 t
+	t60 t; t61 t; t62 t; t63 t; t64 t; t65 t; t66 t; t67 t; t68 t; t69 t
+	t70 t; t71 t; t72 t; t73 t; t74 t; t75 t; t76 t; t77 t; t78 t; t79 t
+	t80 t; t81 t; t82 t; t83 t; t84 t; t85 t; t86 t; t87 t; t88 t; t89 t
+	t90 t; t91 t; t92 t; t93 t; t94 t; t95 t; t96 t; t97 t; t98 t; t99 t
+)
+
+type u99 interface {
+	t00|t01|t02|t03|t04|t05|t06|t07|t08|t09|
+	t10|t11|t12|t13|t14|t15|t16|t17|t18|t19|
+	t20|t21|t22|t23|t24|t25|t26|t27|t28|t29|
+	t30|t31|t32|t33|t34|t35|t36|t37|t38|t39|
+	t40|t41|t42|t43|t44|t45|t46|t47|t48|t49|
+	t50|t51|t52|t53|t54|t55|t56|t57|t58|t59|
+	t60|t61|t62|t63|t64|t65|t66|t67|t68|t69|
+	t70|t71|t72|t73|t74|t75|t76|t77|t78|t79|
+	t80|t81|t82|t83|t84|t85|t86|t87|t88|t89|
+	t90|t91|t92|t93|t94|t95|t96|t97|t98
+}
+
+type u100a interface {
+	u99|float32
+}
+
+type u100b interface {
+	u99|float64
+}
+
+type u101 interface {
+	t00|t01|t02|t03|t04|t05|t06|t07|t08|t09|
+	t10|t11|t12|t13|t14|t15|t16|t17|t18|t19|
+	t20|t21|t22|t23|t24|t25|t26|t27|t28|t29|
+	t30|t31|t32|t33|t34|t35|t36|t37|t38|t39|
+	t40|t41|t42|t43|t44|t45|t46|t47|t48|t49|
+	t50|t51|t52|t53|t54|t55|t56|t57|t58|t59|
+	t60|t61|t62|t63|t64|t65|t66|t67|t68|t69|
+	t70|t71|t72|t73|t74|t75|t76|t77|t78|t79|
+	t80|t81|t82|t83|t84|t85|t86|t87|t88|t89|
+	t90|t91|t92|t93|t94|t95|t96|t97|t98|t99|
+        int // ERROR cannot handle more than 100 union terms
+}
+
+type u102 interface {
+        int /* ERROR cannot handle more than 100 union terms */ |string|u100a
+}
+
+type u200 interface {
+        u100a /* ERROR cannot handle more than 100 union terms */ |u100b
+}
diff --git a/src/internal/types/testdata/check/vardecl.go b/src/internal/types/testdata/check/vardecl.go
new file mode 100644
index 0000000..5b68adb
--- /dev/null
+++ b/src/internal/types/testdata/check/vardecl.go
@@ -0,0 +1,215 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package vardecl
+
+// Prerequisites.
+import "math"
+func f() {}
+func g() (x, y int) { return }
+var m map[string]int
+
+// Var decls must have a type or an initializer.
+var _ int
+var _, _ int
+
+var _; /* ERROR "expected type" */
+var _, _; /* ERROR "expected type" */
+var _, _, _; /* ERROR "expected type" */
+
+// The initializer must be an expression.
+var _ = int /* ERROR "not an expression" */
+var _ = f /* ERROR "used as value" */ ()
+
+// Identifier and expression arity must match.
+var _, _ = 1, 2
+var _ = 1, 2 /* ERROR "extra init expr 2" */
+var _, _ = 1 /* ERROR "assignment mismatch: [1-9]+ variables but.*[1-9]+ value(s)?" */
+var _, _, _ /* ERROR "missing init expr for _" */ = 1, 2
+
+var _ = g /* ERROR "multiple-value g" */ ()
+var _, _ = g()
+var _, _, _ = g /* ERROR "assignment mismatch: [1-9]+ variables but.*[1-9]+ value(s)?" */ ()
+
+var _ = m["foo"]
+var _, _ = m["foo"]
+var _, _, _ = m  /* ERROR "assignment mismatch: [1-9]+ variables but.*[1-9]+ value(s)?" */ ["foo"]
+
+var _, _ int = 1, 2
+var _ int = 1, 2 /* ERROR "extra init expr 2" */
+var _, _ int = 1 /* ERROR "assignment mismatch: [1-9]+ variables but.*[1-9]+ value(s)?" */
+var _, _, _ /* ERROR "missing init expr for _" */ int = 1, 2
+
+var (
+	_, _ = 1, 2
+	_ = 1, 2 /* ERROR "extra init expr 2" */
+	_, _ = 1 /* ERROR "assignment mismatch: [1-9]+ variables but.*[1-9]+ value(s)?" */
+	_, _, _ /* ERROR "missing init expr for _" */ = 1, 2
+
+	_ = g /* ERROR "multiple-value g" */ ()
+	_, _ = g()
+	_, _, _ = g /* ERROR "assignment mismatch: [1-9]+ variables but.*[1-9]+ value(s)?" */ ()
+
+	_ = m["foo"]
+	_, _ = m["foo"]
+	_, _, _ = m /* ERROR "assignment mismatch: [1-9]+ variables but.*[1-9]+ value(s)?" */ ["foo"]
+
+	_, _ int = 1, 2
+	_ int = 1, 2 /* ERROR "extra init expr 2" */
+	_, _ int = 1 /* ERROR "assignment mismatch: [1-9]+ variables but.*[1-9]+ value(s)?" */
+	_, _, _ /* ERROR "missing init expr for _" */ int = 1, 2
+)
+
+// Variables declared in function bodies must be 'used'.
+type T struct{}
+func (r T) _(a, b, c int) (u, v, w int) {
+	var x1 /* ERROR "declared and not used" */ int
+	var x2 /* ERROR "declared and not used" */ int
+	x1 = 1
+	(x2) = 2
+
+	y1 /* ERROR "declared and not used" */ := 1
+	y2 /* ERROR "declared and not used" */ := 2
+	y1 = 1
+	(y1) = 2
+
+	{
+		var x1 /* ERROR "declared and not used" */ int
+		var x2 /* ERROR "declared and not used" */ int
+		x1 = 1
+		(x2) = 2
+
+		y1 /* ERROR "declared and not used" */ := 1
+		y2 /* ERROR "declared and not used" */ := 2
+		y1 = 1
+		(y1) = 2
+	}
+
+	if x /* ERROR "declared and not used" */ := 0; a < b {}
+
+	switch x /* ERROR "declared and not used" */, y := 0, 1; a {
+	case 0:
+		_ = y
+	case 1:
+		x /* ERROR "declared and not used" */ := 0
+	}
+
+	var t interface{}
+	switch t /* ERROR "declared and not used" */ := t.(type) {}
+
+	switch t /* ERROR "declared and not used" */ := t.(type) {
+	case int:
+	}
+
+	switch t /* ERROR "declared and not used" */ := t.(type) {
+	case int:
+	case float32, complex64:
+		t = nil
+	}
+
+	switch t := t.(type) {
+	case int:
+	case float32, complex64:
+		_ = t
+	}
+
+	switch t := t.(type) {
+	case int:
+	case float32:
+	case string:
+		_ = func() string {
+			return t
+		}
+	}
+
+	switch t := t; t /* ERROR "declared and not used" */ := t.(type) {}
+
+	var z1 /* ERROR "declared and not used" */ int
+	var z2 int
+	_ = func(a, b, c int) (u, v, w int) {
+		z1 = a
+		(z1) = b
+		a = z2
+		return
+	}
+
+	var s []int
+	var i /* ERROR "declared and not used" */ , j int
+	for i, j = range s {
+		_ = j
+	}
+
+	for i, j /* ERROR "declared and not used" */ := range s {
+		_ = func() int {
+			return i
+		}
+	}
+	return
+}
+
+// Unused variables in function literals must lead to only one error (issue #22524).
+func _() {
+	_ = func() {
+		var x /* ERROR declared and not used */ int
+	}
+}
+
+// Invalid variable declarations must not lead to "declared and not used errors".
+// TODO(gri) enable these tests once go/types follows types2 logic for declared and not used variables
+// func _() {
+//	var a x                        // DISABLED_ERROR undefined: x
+//	var b = x                      // DISABLED_ERROR undefined: x
+//	var c int = x                  // DISABLED_ERROR undefined: x
+//	var d, e, f x                  /* DISABLED_ERROR x */ /* DISABLED_ERROR x */ /* DISABLED_ERROR x */
+//	var g, h, i = x, x, x          /* DISABLED_ERROR x */ /* DISABLED_ERROR x */ /* DISABLED_ERROR x */
+//	var j, k, l float32 = x, x, x  /* DISABLED_ERROR x */ /* DISABLED_ERROR x */ /* DISABLED_ERROR x */
+//	// but no "declared and not used" errors
+// }
+
+// Invalid (unused) expressions must not lead to spurious "declared and not used errors".
+func _() {
+	var a, b, c int
+	var x, y int
+	x, y = a /* ERROR "assignment mismatch: [1-9]+ variables but.*[1-9]+ value(s)?" */ , b, c
+	_ = x
+	_ = y
+}
+
+func _() {
+	var x int
+	return x /* ERROR too many return values */
+	return math /* ERROR too many return values */ .Sin(0)
+}
+
+func _() int {
+	var x, y int
+	return x, y /* ERROR too many return values */
+}
+
+// Short variable declarations must declare at least one new non-blank variable.
+func _() {
+	_ := /* ERROR no new variables */ 0
+	_, a := 0, 1
+	_, a := /* ERROR no new variables */ 0, 1
+	_, a, b := 0, 1, 2
+	_, _, _ := /* ERROR no new variables */ 0, 1, 2
+
+	_ = a
+	_ = b
+}
+
+// Test case for variables depending on function literals (see also #22992).
+var A /* ERROR initialization cycle */ = func() int { return A }()
+
+func _() {
+	// The function literal below must not see a.
+	var a = func() int { return a /* ERROR "undefined" */ }()
+	var _ = func() int { return a }()
+
+	// The function literal below must not see x, y, or z.
+	var x, y, z = 0, 1, func() int { return x /* ERROR "undefined" */ + y /* ERROR "undefined" */ + z /* ERROR "undefined" */ }()
+	_, _, _ = x, y, z
+}
+
+// TODO(gri) consolidate other var decl checks in this file
\ No newline at end of file
diff --git a/src/internal/types/testdata/examples/constraints.go b/src/internal/types/testdata/examples/constraints.go
new file mode 100644
index 0000000..5b14489
--- /dev/null
+++ b/src/internal/types/testdata/examples/constraints.go
@@ -0,0 +1,80 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file shows some examples of generic constraint interfaces.
+
+package p
+
+type MyInt int
+
+type (
+	// Arbitrary types may be embedded like interfaces.
+	_ interface{int}
+	_ interface{~int}
+
+	// Types may be combined into a union.
+	union interface{int|~string}
+
+	// Union terms must describe disjoint (non-overlapping) type sets.
+	_ interface{int|int /* ERROR overlapping terms int */ }
+	_ interface{int|~ /* ERROR overlapping terms ~int */ int }
+	_ interface{~int|~ /* ERROR overlapping terms ~int */ int }
+	_ interface{~int|MyInt /* ERROR overlapping terms p.MyInt and ~int */ }
+	_ interface{int|any}
+	_ interface{int|~string|union}
+	_ interface{int|~string|interface{int}}
+	_ interface{union|int}   // interfaces (here: union) are ignored when checking for overlap
+	_ interface{union|union} // ditto
+
+	// For now we do not permit interfaces with methods in unions.
+	_ interface{~ /* ERROR invalid use of ~ */ any}
+	_ interface{int|interface /* ERROR cannot use .* in union */ { m() }}
+)
+
+type (
+	// Tilde is not permitted on defined types or interfaces.
+	foo int
+	bar any
+	_ interface{foo}
+	_ interface{~ /* ERROR invalid use of ~ */ foo }
+	_ interface{~ /* ERROR invalid use of ~ */ bar }
+)
+
+// Stand-alone type parameters are not permitted as elements or terms in unions.
+type (
+	_[T interface{ *T } ] struct{}        // ok
+	_[T interface{ int | *T } ] struct{}  // ok
+	_[T interface{ T /* ERROR term cannot be a type parameter */ } ] struct{}
+	_[T interface{ ~T /* ERROR type in term ~T cannot be a type parameter */ } ] struct{}
+	_[T interface{ int|T /* ERROR term cannot be a type parameter */ }] struct{}
+)
+
+// Multiple embedded union elements are intersected. The order in which they
+// appear in the interface doesn't matter since intersection is a symmetric
+// operation.
+
+type myInt1 int
+type myInt2 int
+
+func _[T interface{ myInt1|myInt2; ~int }]() T { return T(0) }
+func _[T interface{ ~int; myInt1|myInt2 }]() T { return T(0) }
+
+// Here the intersections are empty - there's no type that's in the type set of T.
+func _[T interface{ myInt1|myInt2; int }]() T { return T(0 /* ERROR cannot convert */ ) }
+func _[T interface{ int; myInt1|myInt2 }]() T { return T(0 /* ERROR cannot convert */ ) }
+
+// Union elements may be interfaces as long as they don't define
+// any methods or embed comparable.
+
+type (
+	Integer interface{ ~int|~int8|~int16|~int32|~int64 }
+	Unsigned interface{ ~uint|~uint8|~uint16|~uint32|~uint64 }
+	Floats interface{ ~float32|~float64 }
+	Complex interface{ ~complex64|~complex128 }
+	Number interface{ Integer|Unsigned|Floats|Complex }
+	Ordered interface{ Integer|Unsigned|Floats|~string }
+
+	_ interface{ Number | error /* ERROR cannot use error in union */ }
+	_ interface{ Ordered | comparable /* ERROR cannot use comparable in union */ }
+)
diff --git a/src/internal/types/testdata/examples/functions.go b/src/internal/types/testdata/examples/functions.go
new file mode 100644
index 0000000..47e1c35
--- /dev/null
+++ b/src/internal/types/testdata/examples/functions.go
@@ -0,0 +1,219 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file shows some examples of type-parameterized functions.
+
+package p
+
+// Reverse is a generic function that takes a []T argument and
+// reverses that slice in place.
+func Reverse[T any](list []T) {
+	i := 0
+	j := len(list)-1
+	for i < j {
+		list[i], list[j] = list[j], list[i]
+		i++
+		j--
+	}
+}
+
+func _() {
+	// Reverse can be called with an explicit type argument.
+	Reverse[int](nil)
+	Reverse[string]([]string{"foo", "bar"})
+	Reverse[struct{x, y int}]([]struct{x, y int}{{1, 2}, {2, 3}, {3, 4}})
+
+	// Since the type parameter is used for an incoming argument,
+	// it can be inferred from the provided argument's type.
+	Reverse([]string{"foo", "bar"})
+	Reverse([]struct{x, y int}{{1, 2}, {2, 3}, {3, 4}})
+
+	// But the incoming argument must have a type, even if it's a
+	// default type. An untyped nil won't work.
+	// Reverse(nil) // this won't type-check
+
+	// A typed nil will work, though.
+	Reverse([]int(nil))
+}
+
+// Certain functions, such as the built-in `new` could be written using
+// type parameters.
+func new[T any]() *T {
+	var x T
+	return &x
+}
+
+// When calling our own `new`, we need to pass the type parameter
+// explicitly since there is no (value) argument from which the
+// result type could be inferred. We don't try to infer the
+// result type from the assignment to keep things simple and
+// easy to understand.
+var _ = new[int]()
+var _ *float64 = new[float64]() // the result type is indeed *float64
+
+// A function may have multiple type parameters, of course.
+func foo[A, B, C any](a A, b []B, c *C) B {
+	// do something here
+	return b[0]
+}
+
+// As before, we can pass type parameters explicitly.
+var s = foo[int, string, float64](1, []string{"first"}, new[float64]())
+
+// Or we can use type inference.
+var _ float64 = foo(42, []float64{1.0}, &s)
+
+// Type inference works in a straight-forward manner even
+// for variadic functions.
+func variadic[A, B any](A, B, ...B) int { panic(0) }
+
+// var _ = variadic(1) // ERROR not enough arguments
+var _ = variadic(1, 2.3)
+var _ = variadic(1, 2.3, 3.4, 4.5)
+var _ = variadic[int, float64](1, 2.3, 3.4, 4)
+
+// Type inference also works in recursive function calls where
+// the inferred type is the type parameter of the caller.
+func f1[T any](x T) {
+	f1(x)
+}
+
+func f2a[T any](x, y T) {
+	f2a(x, y)
+}
+
+func f2b[T any](x, y T) {
+	f2b(y, x)
+}
+
+func g2a[P, Q any](x P, y Q) {
+	g2a(x, y)
+}
+
+func g2b[P, Q any](x P, y Q) {
+	g2b(y, x)
+}
+
+// Here's an example of a recursive function call with variadic
+// arguments and type inference inferring the type parameter of
+// the caller (i.e., itself).
+func max[T interface{ ~int }](x ...T) T {
+	var x0 T
+	if len(x) > 0 {
+		x0 = x[0]
+	}
+	if len(x) > 1 {
+		x1 := max(x[1:]...)
+		if x1 > x0 {
+			return x1
+		}
+	}
+	return x0
+}
+
+// When inferring channel types, the channel direction is ignored
+// for the purpose of type inference. Once the type has been in-
+// fered, the usual parameter passing rules are applied.
+// Thus even if a type can be inferred successfully, the function
+// call may not be valid.
+
+func fboth[T any](chan T) {}
+func frecv[T any](<-chan T) {}
+func fsend[T any](chan<- T) {}
+
+func _() {
+	var both chan int
+	var recv <-chan int
+	var send chan<-int
+
+	fboth(both)
+	fboth(recv /* ERROR cannot use */ )
+	fboth(send /* ERROR cannot use */ )
+
+	frecv(both)
+	frecv(recv)
+	frecv(send /* ERROR cannot use */ )
+
+	fsend(both)
+	fsend(recv /* ERROR cannot use */)
+	fsend(send)
+}
+
+func ffboth[T any](func(chan T)) {}
+func ffrecv[T any](func(<-chan T)) {}
+func ffsend[T any](func(chan<- T)) {}
+
+func _() {
+	var both func(chan int)
+	var recv func(<-chan int)
+	var send func(chan<- int)
+
+	ffboth(both)
+	ffboth(recv /* ERROR cannot use */ )
+	ffboth(send /* ERROR cannot use */ )
+
+	ffrecv(both /* ERROR cannot use */ )
+	ffrecv(recv)
+	ffrecv(send /* ERROR cannot use */ )
+
+	ffsend(both /* ERROR cannot use */ )
+	ffsend(recv /* ERROR cannot use */ )
+	ffsend(send)
+}
+
+// When inferring elements of unnamed composite parameter types,
+// if the arguments are defined types, use their underlying types.
+// Even though the matching types are not exactly structurally the
+// same (one is a type literal, the other a named type), because
+// assignment is permitted, parameter passing is permitted as well,
+// so type inference should be able to handle these cases well.
+
+func g1[T any]([]T) {}
+func g2[T any]([]T, T) {}
+func g3[T any](*T, ...T) {}
+
+func _() {
+	type intSlize []int
+	g1([]int{})
+	g1(intSlize{})
+	g2(nil, 0)
+
+	type myString string
+	var s1 string
+	g3(nil, "1", myString("2"), "3")
+	g3(& /* ERROR does not match */ s1, "1", myString("2"), "3")
+	_ = s1
+
+	type myStruct struct{x int}
+	var s2 myStruct
+	g3(nil, struct{x int}{}, myStruct{})
+	g3(&s2, struct{x int}{}, myStruct{})
+	g3(nil, myStruct{}, struct{x int}{})
+	g3(&s2, myStruct{}, struct{x int}{})
+}
+
+// Here's a realistic example.
+
+func append[T any](s []T, t ...T) []T { panic(0) }
+
+func _() {
+	var f func()
+	type Funcs []func()
+	var funcs Funcs
+	_ = append(funcs, f)
+}
+
+// Generic type declarations cannot have empty type parameter lists
+// (that would indicate a slice type). Thus, generic functions cannot
+// have empty type parameter lists, either. This is a syntax error.
+
+func h[] /* ERROR empty type parameter list */ () {}
+
+func _() {
+	h /* ERROR cannot index */ [] /* ERROR operand */ ()
+}
+
+// Generic functions must have a function body.
+
+func _ /* ERROR generic function is missing function body */ [P any]()
diff --git a/src/internal/types/testdata/examples/inference.go b/src/internal/types/testdata/examples/inference.go
new file mode 100644
index 0000000..073df9c
--- /dev/null
+++ b/src/internal/types/testdata/examples/inference.go
@@ -0,0 +1,116 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file shows some examples of type inference.
+
+package p
+
+type Ordered interface {
+	~int | ~float64 | ~string
+}
+
+func min[T Ordered](x, y T) T { panic(0) }
+
+func _() {
+	// min can be called with explicit instantiation.
+	_ = min[int](1, 2)
+
+	// Alternatively, the type argument can be inferred from
+	// one of the arguments. Untyped arguments will be considered
+	// last.
+	var x int
+	_ = min(x, x)
+	_ = min(x, 1)
+	_ = min(x, 1.0)
+	_ = min(1, 2)
+	_ = min(1, 2.3 /* ERROR default type float64 .* does not match */)
+
+	var y float64
+	_ = min(1, y)
+	_ = min(1.2, y)
+	_ = min(1.2, 3.4)
+	_ = min(1.2, 3 /* ERROR default type int .* does not match */)
+
+	var s string
+	_ = min(s, "foo")
+	_ = min("foo", "bar")
+}
+
+func mixed[T1, T2, T3 any](T1, T2, T3) {}
+
+func _() {
+	// mixed can be called with explicit instantiation.
+	mixed[int, string, bool](0, "", false)
+
+	// Alternatively, partial type arguments may be provided
+	// (from left to right), and the other may be inferred.
+	mixed[int, string](0, "", false)
+	mixed[int](0, "", false)
+	mixed(0, "", false)
+
+	// Provided type arguments always take precedence over
+	// inferred types.
+	mixed[int, string](1.1 /* ERROR cannot use 1.1 */, "", false)
+}
+
+func related1[Slice interface{ ~[]Elem }, Elem any](s Slice, e Elem) {}
+
+func _() {
+	// related1 can be called with explicit instantiation.
+	var si []int
+	related1[[]int, int](si, 0)
+
+	// Alternatively, the 2nd type argument can be inferred
+	// from the first one through constraint type inference.
+	var ss []string
+	_ = related1[[]string]
+	related1[[]string](ss, "foo")
+
+	// A type argument inferred from another explicitly provided
+	// type argument overrides whatever value argument type is given.
+	related1[[]string](ss, 0 /* ERROR cannot use 0 */)
+
+	// A type argument may be inferred from a value argument
+	// and then help infer another type argument via constraint
+	// type inference.
+	related1(si, 0)
+	related1(si, "foo" /* ERROR cannot use "foo" */)
+}
+
+func related2[Elem any, Slice interface{ []Elem }](e Elem, s Slice) {}
+
+func _() {
+	// related2 can be called with explicit instantiation.
+	var si []int
+	related2[int, []int](0, si)
+
+	// Alternatively, the 2nd type argument can be inferred
+	// from the first one through constraint type inference.
+	var ss []string
+	_ = related2[string]
+	related2[string]("foo", ss)
+
+	// A type argument may be inferred from a value argument
+	// and then help infer another type argument via constraint
+	// type inference. Untyped arguments are always considered
+	// last.
+	related2(1.2, []float64{})
+	related2(1.0, []int{})
+	related2 /* ERROR does not satisfy */ (float64(1.0), []int{}) // TODO(gri) fix error position
+}
+
+type List[P any] []P
+
+func related3[Elem any, Slice []Elem | List[Elem]]() Slice { return nil }
+
+func _() {
+	// related3 can be instantiated explicitly
+	related3[int, []int]()
+	related3[byte, List[byte]]()
+
+	// The 2nd type argument cannot be inferred from the first
+	// one because there's two possible choices: []Elem and
+	// List[Elem].
+	related3 /* ERROR cannot infer Slice */ [int]()
+}
diff --git a/src/internal/types/testdata/examples/methods.go b/src/internal/types/testdata/examples/methods.go
new file mode 100644
index 0000000..a46f789
--- /dev/null
+++ b/src/internal/types/testdata/examples/methods.go
@@ -0,0 +1,112 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file shows some examples of methods on type-parameterized types.
+
+package p
+
+// Parameterized types may have methods.
+type T1[A any] struct{ a A }
+
+// When declaring a method for a parameterized type, the "instantiated"
+// receiver type acts as an implicit declaration of the type parameters
+// for the receiver type. In the example below, method m1 on type T1 has
+// the receiver type T1[A] which declares the type parameter A for use
+// with this method. That is, within the method m1, A stands for the
+// actual type argument provided to an instantiated T1.
+func (t T1[A]) m1() A { return t.a }
+
+// For instance, if T1 is instantiated with the type int, the type
+// parameter A in m1 assumes that type (int) as well and we can write
+// code like this:
+var x T1[int]
+var _ int = x.m1()
+
+// Because the type parameter provided to a parameterized receiver type
+// is declared through that receiver declaration, it must be an identifier.
+// It cannot possibly be some other type because the receiver type is not
+// instantiated with concrete types, it is standing for the parameterized
+// receiver type.
+func (t T1[[ /* ERROR must be an identifier */ ]int]) m2() {}
+
+// Note that using what looks like a predeclared identifier, say int,
+// as type parameter in this situation is deceptive and considered bad
+// style. In m3 below, int is the name of the local receiver type parameter
+// and it shadows the predeclared identifier int which then cannot be used
+// anymore as expected.
+// This is no different from locally re-declaring a predeclared identifier
+// and usually should be avoided. There are some notable exceptions; e.g.,
+// sometimes it makes sense to use the identifier "copy" which happens to
+// also be the name of a predeclared built-in function.
+func (t T1[int]) m3() { var _ int = 42 /* ERROR cannot use 42 .* as int */ }
+
+// The names of the type parameters used in a parameterized receiver
+// type don't have to match the type parameter names in the declaration
+// of the type used for the receiver. In our example, even though T1 is
+// declared with type parameter named A, methods using that receiver type
+// are free to use their own name for that type parameter. That is, the
+// name of type parameters is always local to the declaration where they
+// are introduced. In our example we can write a method m2 and use the
+// name X instead of A for the type parameter w/o any difference.
+func (t T1[X]) m4() X { return t.a }
+
+// If the receiver type is parameterized, type parameters must always be
+// provided: this simply follows from the general rule that a parameterized
+// type must be instantiated before it can be used. A method receiver
+// declaration using a parameterized receiver type is no exception. It is
+// simply that such receiver type expressions perform two tasks simultaneously:
+// they declare the (local) type parameters and then use them to instantiate
+// the receiver type. Forgetting to provide a type parameter leads to an error.
+func (t T1 /* ERROR generic type .* without instantiation */ ) m5() {}
+
+// However, sometimes we don't need the type parameter, and thus it is
+// inconvenient to have to choose a name. Since the receiver type expression
+// serves as a declaration for its type parameters, we are free to choose the
+// blank identifier:
+func (t T1[_]) m6() {}
+
+// Naturally, these rules apply to any number of type parameters on the receiver
+// type. Here are some more complex examples.
+type T2[A, B, C any] struct {
+        a A
+        b B
+        c C
+}
+
+// Naming of the type parameters is local and has no semantic impact:
+func (t T2[A, B, C]) m1() (A, B, C) { return t.a, t.b, t.c }
+func (t T2[C, B, A]) m2() (C, B, A) { return t.a, t.b, t.c }
+func (t T2[X, Y, Z]) m3() (X, Y, Z) { return t.a, t.b, t.c }
+
+// Type parameters may be left blank if they are not needed:
+func (t T2[A, _, C]) m4() (A, C) { return t.a, t.c }
+func (t T2[_, _, X]) m5() X { return t.c }
+func (t T2[_, _, _]) m6() {}
+
+// As usual, blank names may be used for any object which we don't care about
+// using later. For instance, we may write an unnamed method with a receiver
+// that cannot be accessed:
+func (_ T2[_, _, _]) _() int { return 42 }
+
+// Because a receiver parameter list is simply a parameter list, we can
+// leave the receiver argument away for receiver types.
+type T0 struct{}
+func (T0) _() {}
+func (T1[A]) _() {}
+
+// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
+// // A generic receiver type may constrain its type parameter such
+// // that it must be a pointer type. Such receiver types are not
+// // permitted.
+// type T3a[P interface{ ~int | ~string | ~float64 }] P
+// 
+// func (T3a[_]) m() {} // this is ok
+// 
+// type T3b[P interface{ ~unsafe.Pointer }] P
+// 
+// func (T3b /* ERROR invalid receiver */ [_]) m() {}
+// 
+// type T3c[P interface{ *int | *string }] P
+// 
+// func (T3c /* ERROR invalid receiver */ [_]) m() {}
diff --git a/src/internal/types/testdata/examples/operations.go b/src/internal/types/testdata/examples/operations.go
new file mode 100644
index 0000000..18e4d60
--- /dev/null
+++ b/src/internal/types/testdata/examples/operations.go
@@ -0,0 +1,29 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// indirection
+
+func _[P any](p P) {
+        _ = *p // ERROR cannot indirect p
+}
+
+func _[P interface{ int }](p P) {
+        _ = *p // ERROR cannot indirect p
+}
+
+func _[P interface{ *int }](p P) {
+        _ = *p
+}
+
+func _[P interface{ *int | *string }](p P) {
+        _ = *p // ERROR must have identical base types
+}
+
+type intPtr *int
+
+func _[P interface{ *int | intPtr } ](p P) {
+        var _ int = *p
+}
diff --git a/src/internal/types/testdata/examples/types.go b/src/internal/types/testdata/examples/types.go
new file mode 100644
index 0000000..052d168
--- /dev/null
+++ b/src/internal/types/testdata/examples/types.go
@@ -0,0 +1,315 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file shows some examples of generic types.
+
+package p
+
+// List is just what it says - a slice of E elements.
+type List[E any] []E
+
+// A generic (parameterized) type must always be instantiated
+// before it can be used to designate the type of a variable
+// (including a struct field, or function parameter); though
+// for the latter cases, the provided type may be another type
+// parameter. So:
+var _ List[byte] = []byte{}
+
+// A generic binary tree might be declared as follows.
+type Tree[E any] struct {
+	left, right *Tree[E]
+	payload E
+}
+
+// A simple instantiation of Tree:
+var root1 Tree[int]
+
+// The actual type parameter provided may be a generic type itself:
+var root2 Tree[List[int]]
+
+// A couple of more complex examples.
+// We don't need extra parentheses around the element type of the slices on
+// the right (unlike when we use ()'s rather than []'s for type parameters).
+var _ List[List[int]] = []List[int]{}
+var _ List[List[List[Tree[int]]]] = []List[List[Tree[int]]]{}
+
+// Type parameters act like type aliases when used in generic types
+// in the sense that we can "emulate" a specific type instantiation
+// with type aliases.
+type T1[P any] struct {
+	f P
+}
+
+type T2[P any] struct {
+	f struct {
+		g P
+	}
+}
+
+var x1 T1[struct{ g int }]
+var x2 T2[int]
+
+func _() {
+	// This assignment is invalid because the types of x1, x2 are T1(...)
+	// and T2(...) respectively, which are two different defined types.
+	x1 = x2 // ERROR assignment
+
+	// This assignment is valid because the types of x1.f and x2.f are
+	// both struct { g int }; the type parameters act like type aliases
+	// and their actual names don't come into play here.
+	x1.f = x2.f
+}
+
+// We can verify this behavior using type aliases instead:
+type T1a struct {
+	f A1
+}
+type A1 = struct { g int }
+
+type T2a struct {
+	f struct {
+		g A2
+	}
+}
+type A2 = int
+
+var x1a T1a
+var x2a T2a
+
+func _() {
+	x1a = x2a // ERROR assignment
+	x1a.f = x2a.f
+}
+
+// Another interesting corner case are generic types that don't use
+// their type arguments. For instance:
+type T[P any] struct{}
+
+var xint T[int]
+var xbool T[bool]
+
+// Are these two variables of the same type? After all, their underlying
+// types are identical. We consider them to be different because each type
+// instantiation creates a new named type, in this case T<int> and T<bool>
+// even if their underlying types are identical. This is sensible because
+// we might still have methods that have different signatures or behave
+// differently depending on the type arguments, and thus we can't possibly
+// consider such types identical. Consequently:
+func _() {
+	xint = xbool // ERROR assignment
+}
+
+// Generic types cannot be used without instantiation.
+var _ T // ERROR cannot use generic type T
+var _ = T /* ERROR cannot use generic type T */ (0)
+
+// In type context, generic (parameterized) types cannot be parenthesized before
+// being instantiated. See also NOTES entry from 12/4/2019.
+var _ (T /* ERROR cannot use generic type T */ )[ /* ERROR unexpected \[|expected ';' */ int]
+
+// All types may be parameterized, including interfaces.
+type I1[T any] interface{
+	m1(T)
+}
+
+// There is no such thing as a variadic generic type.
+type _[T ... /* ERROR invalid use of ... */ any] struct{}
+
+// Generic interfaces may be embedded as one would expect.
+type I2 interface {
+	I1(int)     // method!
+	I1[string]  // embedded I1
+}
+
+func _() {
+	var x I2
+	x.I1(0)
+	x.m1("foo")
+}
+
+type I0 interface {
+	m0()
+}
+
+type I3 interface {
+	I0
+	I1[bool]
+	m(string)
+}
+
+func _() {
+	var x I3
+	x.m0()
+	x.m1(true)
+	x.m("foo")
+}
+
+type _ struct {
+	( /* ERROR cannot parenthesize */ int8)
+	( /* ERROR cannot parenthesize */ *int16)
+	*( /* ERROR cannot parenthesize */ int32)
+	List[int]
+
+	int8 /* ERROR int8 redeclared */
+	* /* ERROR int16 redeclared */ int16
+	List /* ERROR List redeclared */ [int]
+}
+
+// Issue #45639: We don't allow this anymore. Keep this code
+//               in case we decide to revisit this decision.
+//
+// It's possible to declare local types whose underlying types
+// are type parameters. As with ordinary type definitions, the
+// types underlying properties are "inherited" but the methods
+// are not.
+// func _[T interface{ m(); ~int }]() {
+// 	type L T
+// 	var x L
+// 
+// 	// m is not defined on L (it is not "inherited" from
+// 	// its underlying type).
+// 	x.m /* ERROR x.m undefined */ ()
+// 
+// 	// But the properties of T, such that as that it supports
+// 	// the operations of the types given by its type bound,
+// 	// are also the properties of L.
+// 	x++
+// 	_ = x - x
+// 
+// 	// On the other hand, if we define a local alias for T,
+// 	// that alias stands for T as expected.
+// 	type A = T
+// 	var y A
+// 	y.m()
+// 	_ = y < 0
+// }
+
+// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
+// // It is not permitted to declare a local type whose underlying
+// // type is a type parameter not declared by that type declaration.
+// func _[T any]() {
+// 	type _ T         // ERROR cannot use function type parameter T as RHS in type declaration
+// 	type _ [_ any] T // ERROR cannot use function type parameter T as RHS in type declaration
+// }
+
+// As a special case, an explicit type argument may be omitted
+// from a type parameter bound if the type bound expects exactly
+// one type argument. In that case, the type argument is the
+// respective type parameter to which the type bound applies.
+// Note: We may not permit this syntactic sugar at first.
+// Note: This is now disabled. All examples below are adjusted.
+type Adder[T any] interface {
+	Add(T) T
+}
+
+// We don't need to explicitly instantiate the Adder bound
+// if we have exactly one type parameter.
+func Sum[T Adder[T]](list []T) T {
+	var sum T
+	for _, x := range list {
+		sum = sum.Add(x)
+	}
+	return sum
+}
+
+// Valid and invalid variations.
+type B0 any
+type B1[_ any] any
+type B2[_, _ any] any
+
+func _[T1 B0]() {}
+func _[T1 B1[T1]]() {}
+func _[T1 B2 /* ERROR cannot use generic type .* without instantiation */ ]() {}
+
+func _[T1, T2 B0]() {}
+func _[T1 B1[T1], T2 B1[T2]]() {}
+func _[T1, T2 B2 /* ERROR cannot use generic type .* without instantiation */ ]() {}
+
+func _[T1 B0, T2 B1[T2]]() {} // here B1 applies to T2
+
+// When the type argument is left away, the type bound is
+// instantiated for each type parameter with that type
+// parameter.
+// Note: We may not permit this syntactic sugar at first.
+func _[A Adder[A], B Adder[B], C Adder[A]]() {
+	var a A // A's type bound is Adder[A]
+	a = a.Add(a)
+	var b B // B's type bound is Adder[B]
+	b = b.Add(b)
+	var c C // C's type bound is Adder[A]
+	a = c.Add(a)
+}
+
+// The type of variables (incl. parameters and return values) cannot
+// be an interface with type constraints or be/embed comparable.
+type I interface {
+	~int
+}
+
+var (
+	_ interface /* ERROR contains type constraints */ {~int}
+	_ I /* ERROR contains type constraints */
+)
+
+func _(I /* ERROR contains type constraints */ )
+func _(x, y, z I /* ERROR contains type constraints */ )
+func _() I /* ERROR contains type constraints */
+
+func _() {
+	var _ I /* ERROR contains type constraints */
+}
+
+type C interface {
+	comparable
+}
+
+var _ comparable /* ERROR comparable */
+var _ C /* ERROR comparable */
+
+func _(_ comparable /* ERROR comparable */ , _ C /* ERROR comparable */ )
+
+func _() {
+	var _ comparable /* ERROR comparable */
+	var _ C /* ERROR comparable */
+}
+
+// Type parameters are never const types, i.e., it's
+// not possible to declare a constant of type parameter type.
+// (If a type set contains just a single const type, we could
+// allow it, but such type sets don't make much sense in the
+// first place.)
+func _[T interface{~int|~float64}]() {
+	// not valid
+	const _ = T /* ERROR not constant */ (0)
+	const _ T /* ERROR invalid constant type T */ = 1
+
+	// valid
+	var _ = T(0)
+	var _ T = 1
+	_ = T(0)
+}
+
+// It is possible to create composite literals of type parameter
+// type as long as it's possible to create a composite literal
+// of the core type of the type parameter's constraint.
+func _[P interface{ ~[]int }]() P {
+	return P{}
+	return P{1, 2, 3}
+}
+
+func _[P interface{ ~[]E }, E interface{ map[string]P } ]() P {
+	x := P{}
+	return P{{}}
+	return P{E{}}
+	return P{E{"foo": x}}
+	return P{{"foo": x}, {}}
+}
+
+// This is a degenerate case with a singleton type set, but we can create
+// composite literals even if the core type is a defined type.
+type MyInts []int
+
+func _[P MyInts]() P {
+	return P{}
+}
diff --git a/src/internal/types/testdata/examples/typesets.go b/src/internal/types/testdata/examples/typesets.go
new file mode 100644
index 0000000..a50beb9
--- /dev/null
+++ b/src/internal/types/testdata/examples/typesets.go
@@ -0,0 +1,59 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file shows some examples of constraint literals with elided interfaces.
+// These examples are permitted if proposal issue #48424 is accepted.
+
+package p
+
+// Constraint type sets of the form T, ~T, or A|B may omit the interface.
+type (
+	_[T int]            struct{}
+	_[T ~int]           struct{}
+	_[T int | string]   struct{}
+	_[T ~int | ~string] struct{}
+)
+
+func min[T int | string](x, y T) T {
+	if x < y {
+		return x
+	}
+	return y
+}
+
+func lookup[M ~map[K]V, K comparable, V any](m M, k K) V {
+	return m[k]
+}
+
+func deref[P ~*E, E any](p P) E {
+	return *p
+}
+
+func _() int {
+	p := new(int)
+	return deref(p)
+}
+
+func addrOfCopy[V any, P *V](v V) P {
+	return &v
+}
+
+func _() *int {
+	return addrOfCopy(0)
+}
+
+// A type parameter may not be embedded in an interface;
+// so it can also not be used as a constraint.
+func _[A any, B A /* ERROR cannot use a type parameter as constraint */]()    {}
+func _[A any, B, C A /* ERROR cannot use a type parameter as constraint */]() {}
+
+// Error messages refer to the type constraint as it appears in the source.
+// (No implicit interface should be exposed.)
+func _[T string](x T) T {
+	return x /* ERROR constrained by string */ * x
+}
+
+func _[T int | string](x T) T {
+	return x /* ERROR constrained by int|string */ * x
+}
diff --git a/src/internal/types/testdata/fixedbugs/54942.go b/src/internal/types/testdata/fixedbugs/54942.go
new file mode 100644
index 0000000..f2e733b
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/54942.go
@@ -0,0 +1,38 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import (
+	"context"
+	"database/sql"
+)
+
+type I interface {
+	m(int, int, *int, int)
+}
+
+type T struct{}
+
+func (_ *T) m(a, b, c, d int) {}
+
+var _ I = new /* ERROR have m\(int, int, int, int\)\n\t\twant m\(int, int, \*int, int\) */ (T)
+
+// (slightly modified) test case from issue
+
+type Result struct {
+	Value string
+}
+
+type Executor interface {
+	Execute(context.Context, sql.Stmt, int, []sql.NamedArg, int) (Result, error)
+}
+
+type myExecutor struct{}
+
+func (_ *myExecutor) Execute(ctx context.Context, stmt sql.Stmt, maxrows int, args []sql.NamedArg, urgency int) (*Result, error) {
+	return &Result{}, nil
+}
+
+var ex Executor = new /* ERROR have Execute\(context\.Context, sql\.Stmt, int, \[\]sql\.NamedArg, int\) \(\*Result, error\)\n\t\twant Execute\(context\.Context, sql\.Stmt, int, \[\]sql\.NamedArg, int\) \(Result, error\) */ (myExecutor)
diff --git a/src/internal/types/testdata/fixedbugs/issue20583.go b/src/internal/types/testdata/fixedbugs/issue20583.go
new file mode 100644
index 0000000..d26dbad
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue20583.go
@@ -0,0 +1,14 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package issue20583
+
+const (
+	_ = 6e886451608 /* ERROR malformed constant */ /2
+	_ = 6e886451608i /* ERROR malformed constant */ /2
+	_ = 0 * 1e+1000000000 // ERROR malformed constant
+
+	x = 1e100000000
+	_ = x*x*x*x*x*x* /* ERROR not representable */ x
+)
diff --git a/src/internal/types/testdata/fixedbugs/issue23203a.go b/src/internal/types/testdata/fixedbugs/issue23203a.go
new file mode 100644
index 0000000..48cb588
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue23203a.go
@@ -0,0 +1,14 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "unsafe"
+
+type T struct{}
+
+func (T) m1()                         {}
+func (T) m2([unsafe.Sizeof(T.m1)]int) {}
+
+func main() {}
diff --git a/src/internal/types/testdata/fixedbugs/issue23203b.go b/src/internal/types/testdata/fixedbugs/issue23203b.go
new file mode 100644
index 0000000..638ec6c
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue23203b.go
@@ -0,0 +1,14 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "unsafe"
+
+type T struct{}
+
+func (T) m2([unsafe.Sizeof(T.m1)]int) {}
+func (T) m1()                         {}
+
+func main() {}
diff --git a/src/internal/types/testdata/fixedbugs/issue25838.go b/src/internal/types/testdata/fixedbugs/issue25838.go
new file mode 100644
index 0000000..adbd138
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue25838.go
@@ -0,0 +1,26 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// examples from the issue
+
+type (
+	e = f
+	f = g
+	g = []h
+	h i
+	i = j
+	j = e
+)
+
+type (
+	e1 = []h1
+	h1 e1
+)
+
+type (
+	P = *T
+	T P
+)
diff --git a/src/internal/types/testdata/fixedbugs/issue26390.go b/src/internal/types/testdata/fixedbugs/issue26390.go
new file mode 100644
index 0000000..9e0101f
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue26390.go
@@ -0,0 +1,13 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// stand-alone test to ensure case is triggered
+
+package issue26390
+
+type A = T
+
+func (t *T) m() *A { return t }
+
+type T struct{}
diff --git a/src/internal/types/testdata/fixedbugs/issue28251.go b/src/internal/types/testdata/fixedbugs/issue28251.go
new file mode 100644
index 0000000..ef5e61d
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue28251.go
@@ -0,0 +1,65 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file contains test cases for various forms of
+// method receiver declarations, per the spec clarification
+// https://golang.org/cl/142757.
+
+package issue28251
+
+// test case from issue28251
+type T struct{}
+
+type T0 = *T
+
+func (T0) m() {}
+
+func _() { (&T{}).m() }
+
+// various alternative forms
+type (
+        T1 = (((T)))
+)
+
+func ((*(T1))) m1() {}
+func _() { (T{}).m2() }
+func _() { (&T{}).m2() }
+
+type (
+        T2 = (((T3)))
+        T3 = T
+)
+
+func (T2) m2() {}
+func _() { (T{}).m2() }
+func _() { (&T{}).m2() }
+
+type (
+        T4 = ((*(T5)))
+        T5 = T
+)
+
+func (T4) m4() {}
+func _() { (T{}).m4 /* ERROR "cannot call pointer method m4 on T" */ () }
+func _() { (&T{}).m4() }
+
+type (
+        T6 = (((T7)))
+        T7 = (*(T8))
+        T8 = T
+)
+
+func (T6) m6() {}
+func _() { (T{}).m6 /* ERROR "cannot call pointer method m6 on T" */ () }
+func _() { (&T{}).m6() }
+
+type (
+        T9 = *T10
+        T10 = *T11
+        T11 = T
+)
+
+func (T9 /* ERROR invalid receiver type \*\*T */ ) m9() {}
+func _() { (T{}).m9 /* ERROR has no field or method m9 */ () }
+func _() { (&T{}).m9 /* ERROR has no field or method m9 */ () }
diff --git a/src/internal/types/testdata/fixedbugs/issue39634.go b/src/internal/types/testdata/fixedbugs/issue39634.go
new file mode 100644
index 0000000..6ee1548
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39634.go
@@ -0,0 +1,90 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Examples adjusted to match new [T any] syntax for type parameters.
+// Also, previously permitted empty type parameter lists and instantiations
+// are now syntax errors.
+
+package p
+
+// crash 1
+type nt1[_ any]interface{g /* ERROR undefined */ }
+type ph1[e nt1[e],g(d /* ERROR undefined */ )]s /* ERROR undefined */
+func(*ph1[e,e /* ERROR redeclared */ ])h(d /* ERROR undefined */ )
+
+// crash 2
+// Disabled: empty []'s are now syntax errors. This example leads to too many follow-on errors.
+// type Numeric2 interface{t2 /* ERROR not a type */ }
+// func t2[T Numeric2](s[]T){0 /* ERROR not a type */ []{s /* ERROR cannot index */ [0][0]}}
+
+// crash 3
+type t3 *interface{ t3.p /* ERROR t3.p is not a type */ }
+
+// crash 4
+type Numeric4 interface{t4 /* ERROR not a type */ }
+func t4[T Numeric4](s[]T){if( /* ERROR non-boolean */ 0){*s /* ERROR cannot indirect */ [0]}}
+
+// crash 7
+type foo7 interface { bar() }
+type x7[A any] struct{ foo7 }
+func main7() { var _ foo7 = x7[int]{} }
+
+// crash 8
+type foo8[A any] interface { ~A /* ERROR cannot be a type parameter */ }
+func bar8[A foo8[A]](a A) {}
+
+// crash 9
+type foo9[A any] interface { foo9 /* ERROR invalid recursive type */ [A] }
+func _() { var _ = new(foo9[int]) }
+
+// crash 12
+var u /* ERROR cycle */ , i [func /* ERROR used as value */ /* ERROR used as value */ (u, c /* ERROR undefined */ /* ERROR undefined */ ) {}(0, len /* ERROR must be called */ /* ERROR must be called */ )]c /* ERROR undefined */ /* ERROR undefined */
+
+// crash 15
+func y15() { var a /* ERROR declared and not used */ interface{ p() } = G15[string]{} }
+type G15[X any] s /* ERROR undefined */
+func (G15 /* ERROR generic type .* without instantiation */ ) p()
+
+// crash 16
+type Foo16[T any] r16 /* ERROR not a type */
+func r16[T any]() Foo16[Foo16[T]] { panic(0) }
+
+// crash 17
+type Y17 interface{ c() }
+type Z17 interface {
+	c() Y17
+	Y17 /* ERROR duplicate method */
+}
+func F17[T Z17](T) {}
+
+// crash 18
+type o18[T any] []func(_ o18[[]_ /* ERROR cannot use _ */ ])
+
+// crash 19
+type Z19 [][[]Z19{}[0][0]]c19 /* ERROR undefined */
+
+// crash 20
+type Z20 /* ERROR invalid recursive type */ interface{ Z20 }
+func F20[t Z20]() { F20(t /* ERROR invalid composite literal type */ {}) }
+
+// crash 21
+type Z21 /* ERROR invalid recursive type */ interface{ Z21 }
+func F21[T Z21]() { ( /* ERROR not used */ F21[Z21]) }
+
+// crash 24
+type T24[P any] P // ERROR cannot use a type parameter as RHS in type declaration
+func (r T24[P]) m() { T24 /* ERROR without instantiation */ .m() }
+
+// crash 25
+type T25[A any] int
+func (t T25[A]) m1() {}
+var x T25 /* ERROR without instantiation */ .m1
+
+// crash 26
+type T26 = interface{ F26[ /* ERROR interface method must have no type parameters */ Z any]() }
+func F26[Z any]() T26 { return F26[] /* ERROR operand */ }
+
+// crash 27
+func e27[T any]() interface{ x27 /* ERROR not a type */ } { panic(0) }
+func x27() { e27 /* ERROR cannot infer T */ () }
diff --git a/src/internal/types/testdata/fixedbugs/issue39664.go b/src/internal/types/testdata/fixedbugs/issue39664.go
new file mode 100644
index 0000000..3b3ec56
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39664.go
@@ -0,0 +1,15 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T[_ any] struct {}
+
+func (T /* ERROR instantiation */ ) m()
+
+func _() {
+	var x interface { m() }
+	x = T[int]{}
+	_ = x
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue39680.go b/src/internal/types/testdata/fixedbugs/issue39680.go
new file mode 100644
index 0000000..e56bc35
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39680.go
@@ -0,0 +1,31 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// Embedding stand-alone type parameters is not permitted for now. Disabled.
+
+/*
+import "fmt"
+
+// Minimal test case.
+func _[T interface{~T}](x T) T{
+	return x
+}
+
+// Test case from issue.
+type constr[T any] interface {
+	~T
+}
+
+func Print[T constr[T]](s []T) {
+	for _, v := range s {
+		fmt.Print(v)
+	}
+}
+
+func f() {
+	Print([]string{"Hello, ", "playground\n"})
+}
+*/
diff --git a/src/internal/types/testdata/fixedbugs/issue39693.go b/src/internal/types/testdata/fixedbugs/issue39693.go
new file mode 100644
index 0000000..496754d
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39693.go
@@ -0,0 +1,23 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type Number1 interface {
+	// embedding non-interface types is permitted
+	int
+	float64
+}
+
+func Add1[T Number1](a, b T) T {
+	return a /* ERROR not defined */ + b
+}
+
+type Number2 interface {
+	int | float64
+}
+
+func Add2[T Number2](a, b T) T {
+	return a + b
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue39699.go b/src/internal/types/testdata/fixedbugs/issue39699.go
new file mode 100644
index 0000000..72f8399
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39699.go
@@ -0,0 +1,29 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T0 interface{
+}
+
+type T1 interface{
+	~int
+}
+
+type T2 interface{
+	comparable
+}
+
+type T3 interface {
+	T0
+	T1
+	T2
+}
+
+func _() {
+	_ = T0(0)
+	_ = T1 /* ERROR cannot use interface T1 in conversion */ (1)
+	_ = T2 /* ERROR cannot use interface T2 in conversion */ (2)
+	_ = T3 /* ERROR cannot use interface T3 in conversion */ (3)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue39711.go b/src/internal/types/testdata/fixedbugs/issue39711.go
new file mode 100644
index 0000000..d85fa03
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39711.go
@@ -0,0 +1,13 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// Do not report a duplicate type error for this term list.
+// (Check types after interfaces have been completed.)
+type _ interface {
+	// TODO(rfindley) Once we have full type sets we can enable this again.
+	// Fow now we don't permit interfaces in term lists.
+	// type interface{ Error() string }, interface{ String() string }
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue39723.go b/src/internal/types/testdata/fixedbugs/issue39723.go
new file mode 100644
index 0000000..0088523
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39723.go
@@ -0,0 +1,9 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// A constraint must be an interface; it cannot
+// be a type parameter, for instance.
+func _[A interface{ ~int }, B A /* ERROR cannot use a type parameter as constraint */ ]() {}
diff --git a/src/internal/types/testdata/fixedbugs/issue39725.go b/src/internal/types/testdata/fixedbugs/issue39725.go
new file mode 100644
index 0000000..62dc45a
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39725.go
@@ -0,0 +1,16 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f1[T1, T2 any](T1, T2, struct{a T1; b T2}) {}
+func _() {
+	f1(42, string("foo"), struct /* ERROR does not match inferred type struct\{a int; b string\} */ {a, b int}{})
+}
+
+// simplified test case from issue
+func f2[T any](_ []T, _ func(T)) {}
+func _() {
+	f2([]string{}, func /* ERROR does not match inferred type func\(string\) */ (f []byte) {})
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue39754.go b/src/internal/types/testdata/fixedbugs/issue39754.go
new file mode 100644
index 0000000..97365e2
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39754.go
@@ -0,0 +1,21 @@
+// Copyright 2020 The Go Authors. All rights reserved.

+// Use of this source code is governed by a BSD-style

+// license that can be found in the LICENSE file.

+

+package p

+

+type Optional[T any] struct {}

+

+func (_ Optional[T]) Val() (T, bool)

+

+type Box[T any] interface {

+	Val() (T, bool)

+}

+

+func f[V interface{}, A, B Box[V]]() {}

+

+func _() {

+	f[int, Optional[int], Optional[int]]()

+	_ = f[int, Optional[int], Optional /* ERROR does not satisfy Box */ [string]]

+	_ = f[int, Optional[int], Optional /* ERROR Optional.* does not satisfy Box.* */ [string]]

+}

diff --git a/src/internal/types/testdata/fixedbugs/issue39755.go b/src/internal/types/testdata/fixedbugs/issue39755.go
new file mode 100644
index 0000000..257b73a
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39755.go
@@ -0,0 +1,23 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[T interface{~map[string]int}](x T) {
+	_ = x == nil
+}
+
+// simplified test case from issue
+
+type PathParamsConstraint interface {
+        ~map[string]string | ~[]struct{key, value string}
+}
+
+type PathParams[T PathParamsConstraint] struct {
+	t T
+}
+
+func (pp *PathParams[T]) IsNil() bool {
+	return pp.t == nil // this must succeed
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue39768.go b/src/internal/types/testdata/fixedbugs/issue39768.go
new file mode 100644
index 0000000..696d9d9
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39768.go
@@ -0,0 +1,21 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
+// type T[P any] P
+// type A = T  // ERROR cannot use generic type
+// var x A[int]
+// var _ A
+//
+// type B = T[int]
+// var y B = x
+// var _ B /* ERROR not a generic type */ [int]
+
+// test case from issue
+
+type Vector[T any] []T
+type VectorAlias = Vector // ERROR cannot use generic type
+var v Vector[int]
diff --git a/src/internal/types/testdata/fixedbugs/issue39938.go b/src/internal/types/testdata/fixedbugs/issue39938.go
new file mode 100644
index 0000000..633698d
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39938.go
@@ -0,0 +1,54 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// All but E2 and E5 provide an "indirection" and break infinite expansion of a type.
+type E0[P any] []P
+type E1[P any] *P
+type E2[P any] struct{ _ P }
+type E3[P any] struct{ _ *P }
+type E5[P any] struct{ _ [10]P }
+
+type T0 struct {
+        _ E0[T0]
+}
+
+type T0_ struct {
+        E0[T0_]
+}
+
+type T1 struct {
+        _ E1[T1]
+}
+
+type T2 /* ERROR invalid recursive type */ struct {
+        _ E2[T2]
+}
+
+type T3 struct {
+        _ E3[T3]
+}
+
+type T4 /* ERROR invalid recursive type */ [10]E5[T4]
+
+type T5 struct {
+	_ E0[E2[T5]]
+}
+
+type T6 struct {
+	_ E0[E2[E0[E1[E2[[10]T6]]]]]
+}
+
+type T7 struct {
+	_ E0[[10]E2[E0[E2[E2[T7]]]]]
+}
+
+type T8 struct {
+	_ E0[[]E2[E0[E2[E2[T8]]]]]
+}
+
+type T9 /* ERROR invalid recursive type */ [10]E2[E5[E2[T9]]]
+
+type T10 [10]E2[E5[E2[func(T10)]]]
diff --git a/src/internal/types/testdata/fixedbugs/issue39948.go b/src/internal/types/testdata/fixedbugs/issue39948.go
new file mode 100644
index 0000000..c893cc0
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39948.go
@@ -0,0 +1,9 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T[P any] interface{
+	P // ERROR term cannot be a type parameter
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue39976.go b/src/internal/types/testdata/fixedbugs/issue39976.go
new file mode 100644
index 0000000..d703da9
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39976.go
@@ -0,0 +1,16 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type policy[K, V any] interface{}
+type LRU[K, V any] struct{}
+
+func NewCache[K, V any](p policy[K, V]) {}
+
+func _() {
+	var lru LRU[int, string]
+	NewCache[int, string](&lru)
+	NewCache(& /* ERROR does not match policy\[K, V\] \(cannot infer K and V\) */ lru)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue39982.go b/src/internal/types/testdata/fixedbugs/issue39982.go
new file mode 100644
index 0000000..9810b63
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue39982.go
@@ -0,0 +1,36 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type (
+	T[_ any] struct{}
+	S[_ any] struct {
+		data T[*T[int]]
+	}
+)
+
+func _() {
+	_ = S[int]{
+		data: T[*T[int]]{},
+	}
+}
+
+// full test case from issue
+
+type (
+	Element[TElem any] struct{}
+
+	entry[K comparable] struct{}
+
+	Cache[K comparable] struct {
+		data map[K]*Element[*entry[K]]
+	}
+)
+
+func _() {
+	_ = Cache[int]{
+		data: make(map[int](*Element[*entry[int]])),
+	}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue40038.go b/src/internal/types/testdata/fixedbugs/issue40038.go
new file mode 100644
index 0000000..5f81fcb
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue40038.go
@@ -0,0 +1,15 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type A[T any] int
+
+func (A[T]) m(A[T])
+
+func f[P interface{m(P)}]() {}
+
+func _() {
+	_ = f[A[int]]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue40056.go b/src/internal/types/testdata/fixedbugs/issue40056.go
new file mode 100644
index 0000000..66130c0
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue40056.go
@@ -0,0 +1,15 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _() {
+	NewS /* ERROR cannot infer T */ ().M()
+}
+
+type S struct {}
+
+func NewS[T any]() *S { panic(0) }
+
+func (_ *S /* ERROR S is not a generic type */ [T]) M()
diff --git a/src/internal/types/testdata/fixedbugs/issue40057.go b/src/internal/types/testdata/fixedbugs/issue40057.go
new file mode 100644
index 0000000..fdc8fb1
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue40057.go
@@ -0,0 +1,17 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _() {
+	var x interface{}
+	switch t := x.(type) {
+	case S /* ERROR cannot use generic type */ :
+		t.m()
+	}
+}
+
+type S[T any] struct {}
+
+func (_ S[T]) m()
diff --git a/src/internal/types/testdata/fixedbugs/issue40301.go b/src/internal/types/testdata/fixedbugs/issue40301.go
new file mode 100644
index 0000000..c78f9a1
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue40301.go
@@ -0,0 +1,12 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "unsafe"
+
+func _[T any](x T) {
+	_ = unsafe.Alignof(x)
+	_ = unsafe.Sizeof(x)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue40350.go b/src/internal/types/testdata/fixedbugs/issue40350.go
new file mode 100644
index 0000000..08eb426
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue40350.go
@@ -0,0 +1,16 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type number interface {
+	~float64 | ~int | ~int32
+	float64 | ~int32
+}
+
+func f[T number]() {}
+
+func _() {
+	_ = f[int /* ERROR int does not satisfy number \(number mentions int, but int is not in the type set of number\)*/]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue40684.go b/src/internal/types/testdata/fixedbugs/issue40684.go
new file mode 100644
index 0000000..63a058d
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue40684.go
@@ -0,0 +1,15 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T[_ any] int
+
+func f[_ any]() {}
+func g[_, _ any]() {}
+
+func _() {
+	_ = f[T /* ERROR without instantiation */ ]
+	_ = g[T /* ERROR without instantiation */ , T /* ERROR without instantiation */ ]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue40789.go b/src/internal/types/testdata/fixedbugs/issue40789.go
new file mode 100644
index 0000000..9eea4ad
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue40789.go
@@ -0,0 +1,37 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "fmt"
+
+func main() {
+	m := map[string]int{
+		"a": 6,
+		"b": 7,
+	}
+	fmt.Println(copyMap[map[string]int, string, int](m))
+}
+
+type Map[K comparable, V any] interface {
+	map[K] V
+}
+
+func copyMap[M Map[K, V], K comparable, V any](m M) M {
+	m1 := make(M)
+	for k, v := range m {
+		m1[k] = v
+	}
+	return m1
+}
+
+// simpler test case from the same issue
+
+type A[X comparable] interface {
+	[]X
+}
+
+func f[B A[X], X comparable]() B {
+	return nil
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue41124.go b/src/internal/types/testdata/fixedbugs/issue41124.go
new file mode 100644
index 0000000..80d1ff4
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue41124.go
@@ -0,0 +1,91 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// Test case from issue.
+
+type Nat /* ERROR invalid recursive type */ interface {
+	Zero|Succ
+}
+
+type Zero struct{}
+type Succ struct{
+	Nat // Nat contains type constraints but is invalid, so no error
+}
+
+// Struct tests.
+
+type I1 interface {
+	comparable
+}
+
+type I2 interface {
+	~int
+}
+
+type I3 interface {
+	I1
+	I2
+}
+
+type _ struct {
+	f I1 // ERROR interface is .* comparable
+}
+
+type _ struct {
+	comparable // ERROR interface is .* comparable
+}
+
+type _ struct{
+	I1 // ERROR interface is .* comparable
+}
+
+type _ struct{
+	I2 // ERROR interface contains type constraints
+}
+
+type _ struct{
+	I3 // ERROR interface contains type constraints
+}
+
+// General composite types.
+
+type (
+	_ [10]I1 // ERROR interface is .* comparable
+	_ [10]I2 // ERROR interface contains type constraints
+
+	_ []I1 // ERROR interface is .* comparable
+	_ []I2 // ERROR interface contains type constraints
+
+	_ *I3 // ERROR interface contains type constraints
+	_ map[I1 /* ERROR interface is .* comparable */ ]I2 // ERROR interface contains type constraints
+	_ chan I3 // ERROR interface contains type constraints
+	_ func(I1 /* ERROR interface is .* comparable */ )
+	_ func() I2 // ERROR interface contains type constraints
+)
+
+// Other cases.
+
+var _ = [...]I3 /* ERROR interface contains type constraints */ {}
+
+func _(x interface{}) {
+	_ = x.(I3 /* ERROR interface contains type constraints */ )
+}
+
+type T1[_ any] struct{}
+type T3[_, _, _ any] struct{}
+var _ T1[I2 /* ERROR interface contains type constraints */ ]
+var _ T3[int, I2 /* ERROR interface contains type constraints */ , float32]
+
+func f1[_ any]() int { panic(0) }
+var _ = f1[I2 /* ERROR interface contains type constraints */ ]()
+func f3[_, _, _ any]() int { panic(0) }
+var _ = f3[int, I2 /* ERROR interface contains type constraints */ , float32]()
+
+func _(x interface{}) {
+	switch x.(type) {
+	case I2 /* ERROR interface contains type constraints */ :
+	}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue42695.go b/src/internal/types/testdata/fixedbugs/issue42695.go
new file mode 100644
index 0000000..d0d6200
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue42695.go
@@ -0,0 +1,17 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package issue42695
+
+const _ = 6e5518446744 // ERROR malformed constant
+const _ uint8 = 6e5518446744 // ERROR malformed constant
+
+var _ = 6e5518446744 // ERROR malformed constant
+var _ uint8 = 6e5518446744 // ERROR malformed constant
+
+func f(x int) int {
+        return x + 6e5518446744 // ERROR malformed constant
+}
+
+var _ = f(6e5518446744 /* ERROR malformed constant */ )
diff --git a/src/internal/types/testdata/fixedbugs/issue42758.go b/src/internal/types/testdata/fixedbugs/issue42758.go
new file mode 100644
index 0000000..6d75b10
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue42758.go
@@ -0,0 +1,33 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[T any](x interface{}){
+	switch x.(type) {
+	case T: // ok to use a type parameter
+	case int:
+	}
+
+	switch x.(type) {
+	case T:
+	case T /* ERROR duplicate case */ :
+	}
+}
+
+type constraint interface {
+	~int
+}
+
+func _[T constraint](x interface{}){
+	switch x.(type) {
+	case T: // ok to use a type parameter even if type set contains int
+	case int:
+	}
+}
+
+func _(x constraint /* ERROR contains type constraints */ ) {
+	switch x.(type) { // no need to report another error
+	}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue42881.go b/src/internal/types/testdata/fixedbugs/issue42881.go
new file mode 100644
index 0000000..7122d1c
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue42881.go
@@ -0,0 +1,16 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type (
+	T1 interface{ comparable }
+	T2 interface{ int }
+)
+
+var (
+	_ comparable // ERROR cannot use type comparable outside a type constraint: interface is \(or embeds\) comparable
+	_ T1         // ERROR cannot use type T1 outside a type constraint: interface is \(or embeds\) comparable
+	_ T2         // ERROR cannot use type T2 outside a type constraint: interface contains type constraints
+)
diff --git a/src/internal/types/testdata/fixedbugs/issue42987.go b/src/internal/types/testdata/fixedbugs/issue42987.go
new file mode 100644
index 0000000..f58c63f
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue42987.go
@@ -0,0 +1,8 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check that there is only one error (no follow-on errors).
+
+package p
+var _ = [ ... /* ERROR invalid use of \[...\] array */ ]byte("foo")
\ No newline at end of file
diff --git a/src/internal/types/testdata/fixedbugs/issue43056.go b/src/internal/types/testdata/fixedbugs/issue43056.go
new file mode 100644
index 0000000..8ff4e7f
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue43056.go
@@ -0,0 +1,31 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// simplified example
+func f[T ~func(T)](a, b T) {}
+
+type F func(F)
+
+func _() {
+	var i F
+	var j func(F)
+
+	f(i, j)
+	f(j, i)
+}
+
+// example from issue
+func g[T interface{ Equal(T) bool }](a, b T) {}
+
+type I interface{ Equal(I) bool }
+
+func _() {
+	var i I
+	var j interface{ Equal(I) bool }
+
+	g(i, j)
+	g(j, i)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue43087.go b/src/internal/types/testdata/fixedbugs/issue43087.go
new file mode 100644
index 0000000..85d4450
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue43087.go
@@ -0,0 +1,43 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _() {
+	a, b, b /* ERROR b repeated on left side of := */ := 1, 2, 3
+	_ = a
+	_ = b
+}
+
+func _() {
+	a, _, _ := 1, 2, 3 // multiple _'s ok
+	_ = a
+}
+
+func _() {
+	var b int
+	a, b, b /* ERROR b repeated on left side of := */ := 1, 2, 3
+	_ = a
+	_ = b
+}
+
+func _() {
+	var a []int
+	a /* ERROR non-name .* on left side of := */ [0], b := 1, 2
+	_ = a
+	_ = b
+}
+
+func _() {
+	var a int
+	a, a /* ERROR a repeated on left side of := */ := 1, 2
+	_ = a
+}
+
+func _() {
+	var a, b int
+	a, b := /* ERROR no new variables on left side of := */ 1, 2
+	_ = a
+	_ = b
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue43109.go b/src/internal/types/testdata/fixedbugs/issue43109.go
new file mode 100644
index 0000000..f242f16
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue43109.go
@@ -0,0 +1,10 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Ensure there is no "imported and not used" error
+// if a package wasn't imported in the first place.
+
+package p
+
+import . "/foo" // ERROR could not import \/foo
diff --git a/src/internal/types/testdata/fixedbugs/issue43110.go b/src/internal/types/testdata/fixedbugs/issue43110.go
new file mode 100644
index 0000000..8d5c983
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue43110.go
@@ -0,0 +1,43 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type P *struct{}
+
+func _() {
+	// want an error even if the switch is empty
+	var a struct{ _ func() }
+	switch a /* ERROR cannot switch on a */ {
+	}
+
+	switch a /* ERROR cannot switch on a */ {
+	case a: // no follow-on error here
+	}
+
+	// this is ok because f can be compared to nil
+	var f func()
+	switch f {
+	}
+
+	switch f {
+	case nil:
+	}
+
+	switch (func())(nil) {
+	case nil:
+	}
+
+	switch (func())(nil) {
+	case f /* ERROR invalid case f in switch on .* \(func can only be compared to nil\) */ :
+	}
+
+	switch nil /* ERROR use of untyped nil in switch expression */ {
+	}
+
+	// this is ok
+	switch P(nil) {
+	case P(nil):
+	}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue43124.go b/src/internal/types/testdata/fixedbugs/issue43124.go
new file mode 100644
index 0000000..f429f74
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue43124.go
@@ -0,0 +1,16 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+var _ = int(0 /* ERROR invalid use of \.\.\. in conversion to int */ ...)
+
+// test case from issue
+
+type M []string
+
+var (
+	x = []string{"a", "b"}
+	_ = M(x /* ERROR invalid use of \.\.\. in conversion to M */ ...)
+)
diff --git a/src/internal/types/testdata/fixedbugs/issue43125.go b/src/internal/types/testdata/fixedbugs/issue43125.go
new file mode 100644
index 0000000..456888d
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue43125.go
@@ -0,0 +1,8 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+var _ = new(- /* ERROR not a type */ 1)
+var _ = new(1 /* ERROR not a type */ + 1)
diff --git a/src/internal/types/testdata/fixedbugs/issue43190.go b/src/internal/types/testdata/fixedbugs/issue43190.go
new file mode 100644
index 0000000..d1b46b5
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue43190.go
@@ -0,0 +1,31 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// The errors below are produced by the parser, but we check
+// them here for consistency with the types2 tests.
+
+package p
+
+import ; // ERROR missing import path
+import "" // ERROR invalid import path \(empty string\)
+import
+var /* ERROR missing import path */ _ int
+import .; //  ERROR missing import path
+import 'x' // ERROR import path must be a string
+var _ int
+import /* ERROR imports must appear before other declarations */ _ "math"
+
+// Don't repeat previous error for each immediately following import ...
+import ()
+import (.) // ERROR missing import path
+import (
+	"fmt"
+	.
+) // ERROR missing import path
+
+// ... but remind with error again if we start a new import section after
+// other declarations
+var _ = fmt.Println
+import /* ERROR imports must appear before other declarations */ _ "math"
+import _ "math"
diff --git a/src/internal/types/testdata/fixedbugs/issue43527.go b/src/internal/types/testdata/fixedbugs/issue43527.go
new file mode 100644
index 0000000..b515100
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue43527.go
@@ -0,0 +1,16 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+const L = 10
+
+type (
+	_        [L]struct{}
+	_        [A /* ERROR undefined array length A or missing type constraint */ ]struct{}
+	_        [B /* ERROR invalid array length B */ ]struct{}
+	_[A any] struct{}
+
+	B int
+)
diff --git a/src/internal/types/testdata/fixedbugs/issue43671.go b/src/internal/types/testdata/fixedbugs/issue43671.go
new file mode 100644
index 0000000..6879aec
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue43671.go
@@ -0,0 +1,58 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type C0 interface{ int }
+type C1 interface{ chan int }
+type C2 interface{ chan int | <-chan int }
+type C3 interface{ chan int | chan float32 }
+type C4 interface{ chan int | chan<- int }
+type C5[T any] interface{ ~chan T | <-chan T }
+
+func _[T any](ch T) {
+	<-ch // ERROR cannot receive from ch .* \(no core type\)
+}
+
+func _[T C0](ch T) {
+	<-ch // ERROR cannot receive from non-channel ch
+}
+
+func _[T C1](ch T) {
+	<-ch
+}
+
+func _[T C2](ch T) {
+	<-ch
+}
+
+func _[T C3](ch T) {
+	<-ch // ERROR cannot receive from ch .* \(no core type\)
+}
+
+func _[T C4](ch T) {
+	<-ch // ERROR cannot receive from send-only channel
+}
+
+func _[T C5[X], X any](ch T, x X) {
+	x = <-ch
+}
+
+// test case from issue, slightly modified
+type RecvChan[T any] interface {
+	~chan T | ~<-chan T
+}
+
+func _[T any, C RecvChan[T]](ch C) T {
+	return <-ch
+}
+
+func f[T any, C interface{ chan T }](ch C) T {
+	return <-ch
+}
+
+func _(ch chan int) {
+	var x int = f(ch) // test constraint type inference for this case
+	_ = x
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue44688.go b/src/internal/types/testdata/fixedbugs/issue44688.go
new file mode 100644
index 0000000..512bfcc
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue44688.go
@@ -0,0 +1,83 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package P
+
+type A1[T any] struct{}
+
+func (*A1[T]) m1(T) {}
+
+type A2[T any] interface {
+	m2(T)
+}
+
+type B1[T any] struct {
+	filler int
+	*A1[T]
+	A2[T]
+}
+
+type B2[T any] interface {
+	A2[T]
+}
+
+type C[T any] struct {
+	filler1 int
+	filler2 int
+	B1[T]
+}
+
+type D[T any] struct {
+	filler1 int
+	filler2 int
+	filler3 int
+	C[T]
+}
+
+func _() {
+	// calling embedded methods
+	var b1 B1[string]
+
+	b1.A1.m1("")
+	b1.m1("")
+
+	b1.A2.m2("")
+	b1.m2("")
+
+	var b2 B2[string]
+	b2.m2("")
+
+	// a deeper nesting
+	var d D[string]
+	d.m1("")
+	d.m2("")
+
+	// calling method expressions
+	m1x := B1[string].m1
+	m1x(b1, "")
+	m2x := B2[string].m2
+	m2x(b2, "")
+
+	// calling method values
+	m1v := b1.m1
+	m1v("")
+	m2v := b1.m2
+	m2v("")
+	b2v := b2.m2
+	b2v("")
+}
+
+// actual test case from issue
+
+type A[T any] struct{}
+
+func (*A[T]) f(T) {}
+
+type B[T any] struct{ A[T] }
+
+func _() {
+	var b B[string]
+	b.A.f("")
+	b.f("")
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue44799.go b/src/internal/types/testdata/fixedbugs/issue44799.go
new file mode 100644
index 0000000..9e528a7
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue44799.go
@@ -0,0 +1,19 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func Map[F, T any](s []F, f func(F) T) []T { return nil }
+
+func Reduce[Elem1, Elem2 any](s []Elem1, initializer Elem2, f func(Elem2, Elem1) Elem2) Elem2 { var x Elem2; return x }
+
+func main() {
+	var s []int
+	var f1 func(int) float64
+	var f2 func(float64, int) float64
+	_ = Map[int](s, f1)
+	_ = Map(s, f1)
+	_ = Reduce[int](s, 0, f2)
+	_ = Reduce(s, 0, f2)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue45114.go b/src/internal/types/testdata/fixedbugs/issue45114.go
new file mode 100644
index 0000000..0093660
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue45114.go
@@ -0,0 +1,8 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+var s uint
+var _ = string(1 /* ERROR shifted operand 1 .* must be integer */ << s)
diff --git a/src/internal/types/testdata/fixedbugs/issue45548.go b/src/internal/types/testdata/fixedbugs/issue45548.go
new file mode 100644
index 0000000..01c9672
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue45548.go
@@ -0,0 +1,13 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f[F interface{*Q}, G interface{*R}, Q, R any](q Q, r R) {}
+
+func _() {
+	f[*float64, *int](1, 2)
+	f[*float64](1, 2)
+	f(1, 2)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue45550.go b/src/internal/types/testdata/fixedbugs/issue45550.go
new file mode 100644
index 0000000..498b1eb
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue45550.go
@@ -0,0 +1,10 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type Builder /* ERROR invalid recursive type */ [T interface{ struct{ Builder[T] } }] struct{}
+type myBuilder struct {
+	Builder[myBuilder]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue45635.go b/src/internal/types/testdata/fixedbugs/issue45635.go
new file mode 100644
index 0000000..af05ff0
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue45635.go
@@ -0,0 +1,31 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+	some /* ERROR "undefined" */ [int, int]()
+}
+
+type N[T any] struct{}
+
+var _ N [] // ERROR expected type argument list
+
+type I interface {
+	~[]int
+}
+
+func _[T I](i, j int) {
+	var m map[int]int
+	_ = m[i, j /* ERROR "more than one index" */ ]
+
+	var a [3]int
+	_ = a[i, j /* ERROR "more than one index" */ ]
+
+	var s []int
+	_ = s[i, j /* ERROR "more than one index" */ ]
+
+	var t T
+	_ = t[i, j /* ERROR "more than one index" */ ]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue45639.go b/src/internal/types/testdata/fixedbugs/issue45639.go
new file mode 100644
index 0000000..80148fe
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue45639.go
@@ -0,0 +1,13 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package P
+
+// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
+// // It is not permitted to declare a local type whose underlying
+// // type is a type parameters not declared by that type declaration.
+// func _[T any]() {
+// 	type _ T         // ERROR cannot use function type parameter T as RHS in type declaration
+// 	type _ [_ any] T // ERROR cannot use function type parameter T as RHS in type declaration
+// }
diff --git a/src/internal/types/testdata/fixedbugs/issue45920.go b/src/internal/types/testdata/fixedbugs/issue45920.go
new file mode 100644
index 0000000..0a281c5
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue45920.go
@@ -0,0 +1,17 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f1[T any, C chan T | <-chan T](ch C) {}
+
+func _(ch chan int)   { f1(ch) }
+func _(ch <-chan int) { f1(ch) }
+func _(ch chan<- int) { f1 /* ERROR chan<- int does not satisfy chan int \| <-chan int */ (ch) }
+
+func f2[T any, C chan T | chan<- T](ch C) {}
+
+func _(ch chan int)   { f2(ch) }
+func _(ch <-chan int) { f2 /* ERROR <-chan int does not satisfy chan int \| chan<- int */ (ch) }
+func _(ch chan<- int) { f2(ch) }
diff --git a/src/internal/types/testdata/fixedbugs/issue45985.go b/src/internal/types/testdata/fixedbugs/issue45985.go
new file mode 100644
index 0000000..ae04ce2
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue45985.go
@@ -0,0 +1,13 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package issue45985
+
+func app[S interface{ ~[]T }, T any](s S, e T) S {
+	return append(s, e)
+}
+
+func _() {
+	_ = app /* ERROR "int does not match" */ [int]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue46090.go b/src/internal/types/testdata/fixedbugs/issue46090.go
new file mode 100644
index 0000000..07f0101
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue46090.go
@@ -0,0 +1,11 @@
+// -lang=go1.17
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// The predeclared type comparable is not visible before Go 1.18.
+
+package p
+
+type _ comparable // ERROR predeclared comparable
diff --git a/src/internal/types/testdata/fixedbugs/issue46275.go b/src/internal/types/testdata/fixedbugs/issue46275.go
new file mode 100644
index 0000000..0862d5b
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue46275.go
@@ -0,0 +1,26 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package issue46275
+
+type N[T any] struct {
+	*N[T]
+	t T
+}
+
+func (n *N[T]) Elem() T {
+	return n.t
+}
+
+type I interface {
+	Elem() string
+}
+
+func _() {
+	var n1 *N[string]
+	var _ I = n1
+	type NS N[string]
+	var n2 *NS
+	var _ I = n2
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue46403.go b/src/internal/types/testdata/fixedbugs/issue46403.go
new file mode 100644
index 0000000..9d47522
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue46403.go
@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package issue46403
+
+func _() {
+	// a should be used, despite the parser error below.
+	var a []int
+	var _ = a[] // ERROR expected operand
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue46404.go b/src/internal/types/testdata/fixedbugs/issue46404.go
new file mode 100644
index 0000000..e3c93f6
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue46404.go
@@ -0,0 +1,10 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package issue46404
+
+// TODO(gri) re-enable this test with matching errors
+//           between go/types and types2
+// Check that we don't type check t[_] as an instantiation.
+// type t [t /* type parameters must be named */ /* not a generic type */ [_]]_ // cannot use
diff --git a/src/internal/types/testdata/fixedbugs/issue46461.go b/src/internal/types/testdata/fixedbugs/issue46461.go
new file mode 100644
index 0000000..fce06f7
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue46461.go
@@ -0,0 +1,20 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// test case 1
+type T /* ERROR invalid recursive type */ [U interface{ M() T[U] }] int
+
+type X int
+
+func (X) M() T[X] { return 0 }
+
+// test case 2
+type A /* ERROR invalid recursive type */ [T interface{ A[T] }] interface{}
+
+// test case 3
+type A2 /* ERROR invalid recursive type */ [U interface{ A2[U] }] interface{ M() A2[U] }
+
+type I interface{ A2[I]; M() A2[I] }
diff --git a/src/internal/types/testdata/fixedbugs/issue46583.go b/src/internal/types/testdata/fixedbugs/issue46583.go
new file mode 100644
index 0000000..da1f1ff
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue46583.go
@@ -0,0 +1,28 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T1 struct{}
+func (t T1) m(int) {}
+var f1 func(T1)
+
+type T2 struct{}
+func (t T2) m(x int) {}
+var f2 func(T2)
+
+type T3 struct{}
+func (T3) m(int) {}
+var f3 func(T3)
+
+type T4 struct{}
+func (T4) m(x int) {}
+var f4 func(T4)
+
+func _() {
+	f1 = T1 /* ERROR func\(T1, int\) */ .m
+	f2 = T2 /* ERROR func\(t T2, x int\) */ .m
+	f3 = T3 /* ERROR func\(T3, int\) */ .m
+	f4 = T4 /* ERROR func\(_ T4, x int\) */ .m
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue47031.go b/src/internal/types/testdata/fixedbugs/issue47031.go
new file mode 100644
index 0000000..b184f9b
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue47031.go
@@ -0,0 +1,20 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type Mer interface { M() }
+
+func F[T Mer](p *T) {
+	p.M /* ERROR p\.M undefined */ ()
+}
+
+type MyMer int
+
+func (MyMer) M() {}
+
+func _() {
+	F(new(MyMer))
+	F[Mer](nil)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue47115.go b/src/internal/types/testdata/fixedbugs/issue47115.go
new file mode 100644
index 0000000..a0bfe38
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue47115.go
@@ -0,0 +1,40 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type C0 interface{ int }
+type C1 interface{ chan int }
+type C2 interface{ chan int | <-chan int }
+type C3 interface{ chan int | chan float32 }
+type C4 interface{ chan int | chan<- int }
+type C5[T any] interface{ ~chan T | chan<- T }
+
+func _[T any](ch T) {
+	ch <- /* ERROR cannot send to ch .* no core type */ 0
+}
+
+func _[T C0](ch T) {
+	ch <- /* ERROR cannot send to non-channel */ 0
+}
+
+func _[T C1](ch T) {
+	ch <- 0
+}
+
+func _[T C2](ch T) {
+	ch  <-/* ERROR cannot send to receive-only channel */ 0
+}
+
+func _[T C3](ch T) {
+	ch <- /* ERROR cannot send to ch .* no core type */ 0
+}
+
+func _[T C4](ch T) {
+	ch <- 0
+}
+
+func _[T C5[X], X any](ch T, x X) {
+	ch <- x
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue47127.go b/src/internal/types/testdata/fixedbugs/issue47127.go
new file mode 100644
index 0000000..bb4b487
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue47127.go
@@ -0,0 +1,37 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Embedding of stand-alone type parameters is not permitted.
+
+package p
+
+type (
+        _[P any] interface{ *P | []P | chan P | map[string]P }
+        _[P any] interface{ P /* ERROR term cannot be a type parameter */ }
+        _[P any] interface{ ~P /* ERROR type in term ~P cannot be a type parameter */ }
+        _[P any] interface{ int | P /* ERROR term cannot be a type parameter */ }
+        _[P any] interface{ int | ~P /* ERROR type in term ~P cannot be a type parameter */ }
+)
+
+func _[P any]() {
+        type (
+                _[P any] interface{ *P | []P | chan P | map[string]P }
+                _[P any] interface{ P /* ERROR term cannot be a type parameter */ }
+                _[P any] interface{ ~P /* ERROR type in term ~P cannot be a type parameter */ }
+                _[P any] interface{ int | P /* ERROR term cannot be a type parameter */ }
+                _[P any] interface{ int | ~P /* ERROR type in term ~P cannot be a type parameter */ }
+
+                _ interface{ *P | []P | chan P | map[string]P }
+                _ interface{ P /* ERROR term cannot be a type parameter */ }
+                _ interface{ ~P /* ERROR type in term ~P cannot be a type parameter */ }
+                _ interface{ int | P /* ERROR term cannot be a type parameter */ }
+                _ interface{ int | ~P /* ERROR type in term ~P cannot be a type parameter */ }
+        )
+}
+
+func _[P any, Q interface{ *P | []P | chan P | map[string]P }]() {}
+func _[P any, Q interface{ P /* ERROR term cannot be a type parameter */ }]() {}
+func _[P any, Q interface{ ~P /* ERROR type in term ~P cannot be a type parameter */ }]() {}
+func _[P any, Q interface{ int | P /* ERROR term cannot be a type parameter */ }]() {}
+func _[P any, Q interface{ int | ~P /* ERROR type in term ~P cannot be a type parameter */ }]() {}
diff --git a/src/internal/types/testdata/fixedbugs/issue47411.go b/src/internal/types/testdata/fixedbugs/issue47411.go
new file mode 100644
index 0000000..33b169a
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue47411.go
@@ -0,0 +1,26 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f[_ comparable]() {}
+func g[_ interface{interface{comparable; ~int|~string}}]() {}
+
+func _[P comparable,
+        Q interface{ comparable; ~int|~string },
+        R any,                               // not comparable
+        S interface{ comparable; ~func() },  // not comparable
+]() {
+        _ = f[int]
+        _ = f[P]
+        _ = f[Q]
+        _ = f[func /* ERROR does not satisfy comparable */ ()]
+        _ = f[R /* ERROR R does not satisfy comparable */ ]
+
+        _ = g[int]
+        _ = g[P /* ERROR P does not satisfy interface{interface{comparable; ~int \| ~string} */ ]
+        _ = g[Q]
+        _ = g[func /* ERROR func\(\) does not satisfy interface{interface{comparable; ~int \| ~string}} */ ()]
+        _ = g[R /* ERROR R does not satisfy interface{interface{comparable; ~int \| ~string} */ ]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue47747.go b/src/internal/types/testdata/fixedbugs/issue47747.go
new file mode 100644
index 0000000..6f09fc2
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue47747.go
@@ -0,0 +1,71 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
+// type T1[P any] P
+// 
+// func (T1[_]) m() {}
+// 
+// func _[P any](x *T1[P]) {
+//         // x.m exists because x is of type *T1 where T1 is a defined type
+//         // (even though under(T1) is a type parameter)
+//         x.m()
+// }
+
+
+func _[P interface{ m() }](x P) {
+        x.m()
+        // (&x).m doesn't exist because &x is of type *P
+        // and pointers to type parameters don't have methods
+        (&x).m /* ERROR type \*P is pointer to type parameter, not type parameter */ ()
+}
+
+
+type T2 interface{ m() }
+
+func _(x *T2) {
+        // x.m doesn't exists because x is of type *T2
+        // and pointers to interfaces don't have methods
+        x.m /* ERROR type \*T2 is pointer to interface, not interface */()
+}
+
+// Test case 1 from issue
+
+type Fooer1[t any] interface {
+	Foo(Barer[t])
+}
+type Barer[t any] interface {
+	Bar(t)
+}
+
+// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
+// type Foo1[t any] t
+// type Bar[t any] t
+// 
+// func (l Foo1[t]) Foo(v Barer[t]) { v.Bar(t(l)) }
+// func (b *Bar[t]) Bar(l t)        { *b = Bar[t](l) }
+// 
+// func _[t any](f Fooer1[t]) t {
+// 	var b Bar[t]
+// 	f.Foo(&b)
+// 	return t(b)
+// }
+
+// Test case 2 from issue
+
+// For now, a lone type parameter is not permitted as RHS in a type declaration (issue #45639).
+// type Fooer2[t any] interface {
+// 	Foo()
+// }
+// 
+// type Foo2[t any] t
+// 
+// func (f *Foo2[t]) Foo() {}
+// 
+// func _[t any](v t) {
+// 	var f = Foo2[t](v)
+// 	_ = Fooer2[t](&f)
+// }
diff --git a/src/internal/types/testdata/fixedbugs/issue47796.go b/src/internal/types/testdata/fixedbugs/issue47796.go
new file mode 100644
index 0000000..4c59106
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue47796.go
@@ -0,0 +1,33 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// parameterized types with self-recursive constraints
+type (
+	T1 /* ERROR invalid recursive type */ [P T1[P]]                            interface{}
+	T2 /* ERROR invalid recursive type */ [P, Q T2[P, Q]]                      interface{}
+	T3[P T2[P, Q], Q interface{ ~string }] interface{}
+
+	T4a /* ERROR invalid recursive type */ [P T4a[P]]                                                        interface{ ~int }
+	T4b /* ERROR invalid recursive type */ [P T4b[int]]                                                      interface{ ~int }
+	T4c /* ERROR invalid recursive type */ [P T4c[string]] interface{ ~int }
+
+	// mutually recursive constraints
+	T5 /* ERROR invalid recursive type */ [P T6[P]] interface{ int }
+	T6[P T5[P]] interface{ int }
+)
+
+// verify that constraints are checked as expected
+var (
+	_ T1[int]
+	_ T2[int, string]
+	_ T3[int, string]
+)
+
+// test case from issue
+
+type Eq /* ERROR invalid recursive type */ [a Eq[a]] interface {
+	Equal(that a) bool
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue47818.go b/src/internal/types/testdata/fixedbugs/issue47818.go
new file mode 100644
index 0000000..e9b0adb
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue47818.go
@@ -0,0 +1,61 @@
+// -lang=go1.17
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Parser accepts type parameters but the type checker
+// needs to report any operations that are not permitted
+// before Go 1.18.
+
+package p
+
+type T[P /* ERROR type parameter requires go1\.18 or later */ any /* ERROR predeclared any requires go1\.18 or later */] struct{}
+
+// for init (and main, but we're not in package main) we should only get one error
+func init[P /* ERROR func init must have no type parameters */ any /* ERROR predeclared any requires go1\.18 or later */]() {
+}
+func main[P /* ERROR type parameter requires go1\.18 or later */ any /* ERROR predeclared any requires go1\.18 or later */]() {
+}
+
+func f[P /* ERROR type parameter requires go1\.18 or later */ any /* ERROR predeclared any requires go1\.18 or later */](x P) {
+	var _ T[ /* ERROR type instantiation requires go1\.18 or later */ int]
+	var _ (T[ /* ERROR type instantiation requires go1\.18 or later */ int])
+	_ = T[ /* ERROR type instantiation requires go1\.18 or later */ int]{}
+	_ = T[ /* ERROR type instantiation requires go1\.18 or later */ int](struct{}{})
+}
+
+func (T[ /* ERROR type instantiation requires go1\.18 or later */ P]) g(x int) {
+	f[ /* ERROR function instantiation requires go1\.18 or later */ int](0)     // explicit instantiation
+	(f[ /* ERROR function instantiation requires go1\.18 or later */ int])(0)   // parentheses (different code path)
+	f( /* ERROR implicit function instantiation requires go1\.18 or later */ x) // implicit instantiation
+}
+
+type C1 interface {
+	comparable // ERROR predeclared comparable requires go1\.18 or later
+}
+
+type C2 interface {
+	comparable // ERROR predeclared comparable requires go1\.18 or later
+	int        // ERROR embedding non-interface type int requires go1\.18 or later
+	~ /* ERROR embedding interface element ~int requires go1\.18 or later */ int
+	int /* ERROR embedding interface element int \| ~string requires go1\.18 or later */ | ~string
+}
+
+type _ interface {
+	// errors for these were reported with their declaration
+	C1
+	C2
+}
+
+type (
+	_ comparable // ERROR predeclared comparable requires go1\.18 or later
+	// errors for these were reported with their declaration
+	_ C1
+	_ C2
+
+	_ = comparable // ERROR predeclared comparable requires go1\.18 or later
+	// errors for these were reported with their declaration
+	_ = C1
+	_ = C2
+)
diff --git a/src/internal/types/testdata/fixedbugs/issue47887.go b/src/internal/types/testdata/fixedbugs/issue47887.go
new file mode 100644
index 0000000..4c4fc2f
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue47887.go
@@ -0,0 +1,28 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type Fooer[t any] interface {
+	foo(Barer[t])
+}
+type Barer[t any] interface {
+	bar(Bazer[t])
+}
+type Bazer[t any] interface {
+	Fooer[t]
+	baz(t)
+}
+
+type Int int
+
+func (n Int) baz(int) {}
+func (n Int) foo(b Barer[int]) { b.bar(n) }
+
+type F[t any] interface { f(G[t]) }
+type G[t any] interface { g(H[t]) }
+type H[t any] interface { F[t] }
+
+type T struct{}
+func (n T) f(b G[T]) { b.g(n) }
diff --git a/src/internal/types/testdata/fixedbugs/issue47968.go b/src/internal/types/testdata/fixedbugs/issue47968.go
new file mode 100644
index 0000000..3dd3039
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue47968.go
@@ -0,0 +1,21 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T[P any] struct{}
+
+func (T[P]) m1()
+
+type A1 = T // ERROR cannot use generic type
+
+func (A1[P]) m2() {}
+
+type A2 = T[int]
+
+func (A2 /* ERROR cannot define new methods on instantiated type T\[int\] */) m3()   {}
+func (_ /* ERROR cannot define new methods on instantiated type T\[int\] */ A2) m4() {}
+
+func (T[int]) m5()                                     {} // int is the type parameter name, not an instantiation
+func (T[* /* ERROR must be an identifier */ int]) m6() {} // syntax error
diff --git a/src/internal/types/testdata/fixedbugs/issue48008.go b/src/internal/types/testdata/fixedbugs/issue48008.go
new file mode 100644
index 0000000..6c14c78
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48008.go
@@ -0,0 +1,60 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T[P any] struct{}
+
+func _(x interface{}) {
+	switch x.(type) {
+	case nil:
+	case int:
+
+	case T[int]:
+	case []T[int]:
+	case [10]T[int]:
+	case struct{T[int]}:
+	case *T[int]:
+	case func(T[int]):
+	case interface{m(T[int])}:
+	case map[T[int]] string:
+	case chan T[int]:
+
+	case T /* ERROR cannot use generic type T\[P any\] without instantiation */ :
+	case []T /* ERROR cannot use generic type */ :
+	case [10]T /* ERROR cannot use generic type */ :
+	case struct{T /* ERROR cannot use generic type */ }:
+	case *T /* ERROR cannot use generic type */ :
+	case func(T /* ERROR cannot use generic type */ ):
+	case interface{m(T /* ERROR cannot use generic type */ )}:
+	case map[T /* ERROR cannot use generic type */ ] string:
+	case chan T /* ERROR cannot use generic type */ :
+
+	case T /* ERROR cannot use generic type */ , *T /* ERROR cannot use generic type */ :
+	}
+}
+
+// Make sure a parenthesized nil is ok.
+
+func _(x interface{}) {
+	switch x.(type) {
+	case ((nil)), int:
+	}
+}
+
+// Make sure we look for the predeclared nil.
+
+func _(x interface{}) {
+	type nil int
+	switch x.(type) {
+	case nil: // ok - this is the type nil
+	}
+}
+
+func _(x interface{}) {
+	var nil int
+	switch x.(type) {
+	case nil /* ERROR not a type */ : // not ok - this is the variable nil
+	}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48018.go b/src/internal/types/testdata/fixedbugs/issue48018.go
new file mode 100644
index 0000000..e6ccc6b
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48018.go
@@ -0,0 +1,20 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type Box[A any] struct {
+	value A
+}
+
+func Nest[A /* ERROR instantiation cycle */ any](b Box[A], n int) interface{} {
+	if n == 0 {
+		return b
+	}
+	return Nest(Box[Box[A]]{b}, n-1)
+}
+
+func main() {
+	Nest(Box[int]{0}, 10)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48048.go b/src/internal/types/testdata/fixedbugs/issue48048.go
new file mode 100644
index 0000000..f401330
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48048.go
@@ -0,0 +1,15 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T[P any] struct{}
+
+func (T[_]) A() {}
+
+var _ = (T[int]).A
+var _ = (*T[int]).A
+
+var _ = (T /* ERROR cannot use generic type */).A
+var _ = (*T /* ERROR cannot use generic type */).A
diff --git a/src/internal/types/testdata/fixedbugs/issue48082.go b/src/internal/types/testdata/fixedbugs/issue48082.go
new file mode 100644
index 0000000..5395154
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48082.go
@@ -0,0 +1,7 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package issue48082
+
+import "init" /* ERROR init must be a func */ /* ERROR could not import init */
diff --git a/src/internal/types/testdata/fixedbugs/issue48083.go b/src/internal/types/testdata/fixedbugs/issue48083.go
new file mode 100644
index 0000000..3dae514
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48083.go
@@ -0,0 +1,9 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T[P any] struct{}
+
+type _ interface{ int | T /* ERROR cannot use generic type */ }
\ No newline at end of file
diff --git a/src/internal/types/testdata/fixedbugs/issue48136.go b/src/internal/types/testdata/fixedbugs/issue48136.go
new file mode 100644
index 0000000..b87f84a
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48136.go
@@ -0,0 +1,36 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f1[P interface{ *P }]() {}
+func f2[P interface{ func(P) }]() {}
+func f3[P, Q interface{ func(Q) P }]() {}
+func f4[P interface{ *Q }, Q interface{ func(P) }]() {}
+func f5[P interface{ func(P) }]() {}
+func f6[P interface { *Tree[P] }, Q any ]() {}
+
+func _() {
+        f1 /* ERROR cannot infer P */ ()
+        f2 /* ERROR cannot infer P */ ()
+        f3 /* ERROR cannot infer P */ ()
+        f4 /* ERROR cannot infer P */ ()
+        f5 /* ERROR cannot infer P */ ()
+        f6 /* ERROR cannot infer P */ ()
+}
+
+type Tree[P any] struct {
+        left, right *Tree[P]
+        data P
+}
+
+// test case from issue
+
+func foo[Src interface { func() Src }]() Src {
+        return foo[Src]
+}
+
+func _() {
+        foo /* ERROR cannot infer Src */ ()
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48234.go b/src/internal/types/testdata/fixedbugs/issue48234.go
new file mode 100644
index 0000000..e069930
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48234.go
@@ -0,0 +1,10 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+var _ = interface{
+	m()
+	m /* ERROR "duplicate method" */ ()
+}(nil)
diff --git a/src/internal/types/testdata/fixedbugs/issue48312.go b/src/internal/types/testdata/fixedbugs/issue48312.go
new file mode 100644
index 0000000..2fdb7ca
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48312.go
@@ -0,0 +1,20 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T interface{ m() }
+type P *T
+
+func _(p *T) {
+	p.m /* ERROR type \*T is pointer to interface, not interface */ ()
+}
+
+func _(p P) {
+	p.m /* ERROR type P is pointer to interface, not interface */ ()
+}
+
+func _[P T](p *P) {
+	p.m /* ERROR type \*P is pointer to type parameter, not type parameter */ ()
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48472.go b/src/internal/types/testdata/fixedbugs/issue48472.go
new file mode 100644
index 0000000..2d908f4
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48472.go
@@ -0,0 +1,16 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func g() {
+	var s string
+	var i int
+	_ = s /* ERROR invalid operation: s \+ i \(mismatched types string and int\) */ + i
+}
+
+func f(i int) int {
+        i /* ERROR invalid operation: i \+= "1" \(mismatched types int and untyped string\) */ += "1"
+        return i
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48529.go b/src/internal/types/testdata/fixedbugs/issue48529.go
new file mode 100644
index 0000000..d7a70b1
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48529.go
@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T /* ERROR invalid recursive type */ [U interface{ M() T[U, int] }] int
+
+type X int
+
+func (X) M() T[X] { return 0 }
diff --git a/src/internal/types/testdata/fixedbugs/issue48582.go b/src/internal/types/testdata/fixedbugs/issue48582.go
new file mode 100644
index 0000000..9e1d526
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48582.go
@@ -0,0 +1,29 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type N /* ERROR invalid recursive type */ interface {
+	int | N
+}
+
+type A /* ERROR invalid recursive type */ interface {
+	int | B
+}
+
+type B interface {
+	int | A
+}
+
+type S /* ERROR invalid recursive type */ struct {
+	I // ERROR interface contains type constraints
+}
+
+type I interface {
+	int | S
+}
+
+type P interface {
+	*P // ERROR interface contains type constraints
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48619.go b/src/internal/types/testdata/fixedbugs/issue48619.go
new file mode 100644
index 0000000..72eea1e
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48619.go
@@ -0,0 +1,22 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f[P any](a, _ P) {
+	var x int
+	// TODO(gri) these error messages, while correct, could be better
+	f(a, x /* ERROR type int of x does not match inferred type P for P */)
+	f(x, a /* ERROR type P of a does not match inferred type int for P */)
+}
+
+func g[P any](a, b P) {
+	g(a, b)
+	g(&a, &b)
+	g([]P{}, []P{})
+
+	// work-around: provide type argument explicitly
+	g[*P](&a, &b)
+	g[[]P]([]P{}, []P{})
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48656.go b/src/internal/types/testdata/fixedbugs/issue48656.go
new file mode 100644
index 0000000..0f60f47
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48656.go
@@ -0,0 +1,13 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f[P *Q, Q any](P, Q) {
+	_ = f[P]
+}
+
+func f2[P /* ERROR instantiation cycle */ *Q, Q any](P, Q) {
+	_ = f2[*P]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48695.go b/src/internal/types/testdata/fixedbugs/issue48695.go
new file mode 100644
index 0000000..9f4a768
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48695.go
@@ -0,0 +1,14 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func g[P ~func(T) P, T any](P) {}
+
+func _() {
+	type F func(int) F
+	var f F
+	g(f)
+	_ = g[F]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48703.go b/src/internal/types/testdata/fixedbugs/issue48703.go
new file mode 100644
index 0000000..8a32c1e
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48703.go
@@ -0,0 +1,27 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "unsafe"
+
+// The actual example from the issue.
+type List[P any] struct{}
+
+func (_ List[P]) m() (_ List[List[P]]) { return }
+
+// Other types of recursion through methods.
+type R[P any] int
+
+func (*R[R /* ERROR must be an identifier */ [int]]) m0() {}
+func (R[P]) m1(R[R[P]])                                   {}
+func (R[P]) m2(R[*P])                                     {}
+func (R[P]) m3([unsafe.Sizeof(new(R[P]))]int)             {}
+func (R[P]) m4([unsafe.Sizeof(new(R[R[P]]))]int)          {}
+
+// Mutual recursion
+type M[P any] int
+
+func (R[P]) m5(M[M[P]]) {}
+func (M[P]) m(R[R[P]])  {}
diff --git a/src/internal/types/testdata/fixedbugs/issue48712.go b/src/internal/types/testdata/fixedbugs/issue48712.go
new file mode 100644
index 0000000..63ce7bc
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48712.go
@@ -0,0 +1,41 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[P comparable](x, y P) {
+	_ = x == x
+	_ = x == y
+	_ = y == x
+	_ = y == y
+
+	_ = x /* ERROR type parameter P is not comparable with < */ < y
+}
+
+func _[P comparable](x P, y any) {
+	_ = x == x
+	_ = x == y
+	_ = y == x
+	_ = y == y
+
+	_ = x /* ERROR type parameter P is not comparable with < */ < y
+}
+
+func _[P any](x, y P) {
+	_ = x /* ERROR incomparable types in type set */ == x
+	_ = x /* ERROR incomparable types in type set */ == y
+	_ = y /* ERROR incomparable types in type set */ == x
+	_ = y /* ERROR incomparable types in type set */ == y
+
+	_ = x /* ERROR type parameter P is not comparable with < */ < y
+}
+
+func _[P any](x P, y any) {
+	_ = x /* ERROR incomparable types in type set */ == x
+	_ = x /* ERROR incomparable types in type set */ == y
+	_ = y == x // ERROR incomparable types in type set
+	_ = y == y
+
+	_ = x /* ERROR type parameter P is not comparable with < */ < y
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48819.go b/src/internal/types/testdata/fixedbugs/issue48819.go
new file mode 100644
index 0000000..5d61803
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48819.go
@@ -0,0 +1,15 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "unsafe"
+
+type T /* ERROR invalid recursive type: T refers to itself */ struct {
+	T
+}
+
+func _(t T) {
+	_ = unsafe.Sizeof(t) // should not go into infinite recursion here
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48827.go b/src/internal/types/testdata/fixedbugs/issue48827.go
new file mode 100644
index 0000000..aa1d12a
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48827.go
@@ -0,0 +1,19 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type G[P any] int
+
+type (
+	_ G[int]
+	_ G[G /* ERROR "cannot use.*without instantiation" */]
+	_ bool /* ERROR "invalid operation: bool\[int\] \(bool is not a generic type\)" */ [int]
+	_ bool /* ERROR "invalid operation: bool\[G\] \(bool is not a generic type\)" */[G]
+)
+
+// The example from the issue.
+func _() {
+	_ = &([10]bool /* ERROR "invalid operation.*bool is not a generic type" */ [1 /* ERROR "expected type" */ ]{})
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48951.go b/src/internal/types/testdata/fixedbugs/issue48951.go
new file mode 100644
index 0000000..c94b027
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48951.go
@@ -0,0 +1,21 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type (
+        A1[P any] [10]A1 /* ERROR invalid recursive type */ [P]
+        A2[P any] [10]A2 /* ERROR invalid recursive type */ [*P]
+        A3[P any] [10]*A3[P]
+
+        L1[P any] []L1[P]
+
+        S1[P any] struct{ f S1 /* ERROR invalid recursive type */ [P] }
+        S2[P any] struct{ f S2 /* ERROR invalid recursive type */ [*P] } // like example in issue
+        S3[P any] struct{ f *S3[P] }
+
+        I1[P any] interface{ I1 /* ERROR invalid recursive type */ [P] }
+        I2[P any] interface{ I2 /* ERROR invalid recursive type */ [*P] }
+        I3[P any] interface{ *I3 /* ERROR interface contains type constraints */ [P] }
+)
diff --git a/src/internal/types/testdata/fixedbugs/issue48962.go b/src/internal/types/testdata/fixedbugs/issue48962.go
new file mode 100644
index 0000000..05c681d
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48962.go
@@ -0,0 +1,13 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T0[P any] struct {
+	f P
+}
+
+type T1 /* ERROR invalid recursive type */ struct {
+	_ T0[T1]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue48974.go b/src/internal/types/testdata/fixedbugs/issue48974.go
new file mode 100644
index 0000000..d8ff7c8
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue48974.go
@@ -0,0 +1,22 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type Fooer interface {
+	Foo()
+}
+
+type Fooable[F /* ERROR instantiation cycle */ Fooer] struct {
+	ptr F
+}
+
+func (f *Fooable[F]) Adapter() *Fooable[*FooerImpl[F]] {
+	return &Fooable[*FooerImpl[F]]{&FooerImpl[F]{}}
+}
+
+type FooerImpl[F Fooer] struct {
+}
+
+func (fi *FooerImpl[F]) Foo() {}
diff --git a/src/internal/types/testdata/fixedbugs/issue49003.go b/src/internal/types/testdata/fixedbugs/issue49003.go
new file mode 100644
index 0000000..ece1a27
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49003.go
@@ -0,0 +1,10 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f(s string) int {
+	for range s {
+	}
+} // ERROR missing return
diff --git a/src/internal/types/testdata/fixedbugs/issue49005.go b/src/internal/types/testdata/fixedbugs/issue49005.go
new file mode 100644
index 0000000..5f551b9
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49005.go
@@ -0,0 +1,31 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T1 interface{ M() }
+
+func F1() T1
+
+var _ = F1().(*X1 /* ERROR undefined: X1 */)
+
+func _() {
+	switch F1().(type) {
+	case *X1 /* ERROR undefined: X1 */ :
+	}
+}
+
+type T2 interface{ M() }
+
+func F2() T2
+
+var _ = F2 /* ERROR impossible type assertion: F2\(\)\.\(\*X2\)\n\t\*X2 does not implement T2 \(missing method M\) */ ().(*X2)
+
+type X2 struct{}
+
+func _() {
+	switch F2().(type) {
+	case * /* ERROR impossible type switch case: \*X2\n\tF2\(\) \(value of type T2\) cannot have dynamic type \*X2 \(missing method M\) */ X2:
+	}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue49043.go b/src/internal/types/testdata/fixedbugs/issue49043.go
new file mode 100644
index 0000000..3971cf8
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49043.go
@@ -0,0 +1,24 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// The example from the issue.
+type (
+	N[P any] M /* ERROR invalid recursive type */ [P]
+	M[P any] N[P]
+)
+
+// A slightly more complicated case.
+type (
+	A[P any] B /* ERROR invalid recursive type */ [P]
+	B[P any] C[P]
+	C[P any] A[P]
+)
+
+// Confusing but valid (note that `type T *T` is valid).
+type (
+	N1[P any] *M1[P]
+	M1[P any] *N1[P]
+)
diff --git a/src/internal/types/testdata/fixedbugs/issue49112.go b/src/internal/types/testdata/fixedbugs/issue49112.go
new file mode 100644
index 0000000..dea2608
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49112.go
@@ -0,0 +1,15 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f[P int](P) {}
+
+func _() {
+        _ = f[int]
+        _ = f[[ /* ERROR \[\]int does not satisfy int */ ]int]
+
+        f(0)
+        f/* ERROR \[\]int does not satisfy int */ ([]int{})
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue49179.go b/src/internal/types/testdata/fixedbugs/issue49179.go
new file mode 100644
index 0000000..2ddfa33
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49179.go
@@ -0,0 +1,37 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f1[P int | string]()            {}
+func f2[P ~int | string | float64]() {}
+func f3[P int](x P)                  {}
+
+type myInt int
+type myFloat float64
+
+func _() {
+	_ = f1[int]
+	_ = f1[myInt /* ERROR possibly missing ~ for int in int \| string */]
+	_ = f2[myInt]
+	_ = f2[myFloat /* ERROR possibly missing ~ for float64 in ~int \| string \| float64 */]
+	var x myInt
+	f3 /* ERROR myInt does not satisfy int \(possibly missing ~ for int in int\) */ (x)
+}
+
+// test case from the issue
+
+type SliceConstraint[T any] interface {
+	[]T
+}
+
+func Map[S SliceConstraint[E], E any](s S, f func(E) E) S {
+	return s
+}
+
+type MySlice []int
+
+func f(s MySlice) {
+	Map[MySlice /* ERROR MySlice does not satisfy SliceConstraint\[int\] \(possibly missing ~ for \[\]int in SliceConstraint\[int\]\) */, int](s, nil)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue49242.go b/src/internal/types/testdata/fixedbugs/issue49242.go
new file mode 100644
index 0000000..524a0cb
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49242.go
@@ -0,0 +1,27 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[P int](x P) int {
+	return x // ERROR cannot use x .* as int value in return statement
+}
+
+func _[P int]() int {
+	return P /* ERROR cannot use P\(1\) .* as int value in return statement */ (1)
+}
+
+func _[P int](x int) P {
+        return x // ERROR cannot use x .* as P value in return statement
+}
+
+func _[P, Q any](x P) Q {
+        return x // ERROR cannot use x .* as Q value in return statement
+}
+
+// test case from issue
+func F[G interface{ uint }]() int {
+	f := func(uint) int { return 0 }
+	return f(G /* ERROR cannot use G\(1\) .* as uint value in argument to f */ (1))
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue49247.go b/src/internal/types/testdata/fixedbugs/issue49247.go
new file mode 100644
index 0000000..5be6001
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49247.go
@@ -0,0 +1,20 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type integer interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr
+}
+
+func Add1024[T integer](s []T) {
+	for i, v := range s {
+		s[i] = v + 1024 // ERROR cannot convert 1024 \(untyped int constant\) to type T
+	}
+}
+
+func f[T interface{ int8 }]() {
+	println(T(1024 /* ERROR cannot convert 1024 \(untyped int value\) to type T */))
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue49276.go b/src/internal/types/testdata/fixedbugs/issue49276.go
new file mode 100644
index 0000000..ab5794a
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49276.go
@@ -0,0 +1,46 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "unsafe"
+
+type S /* ERROR invalid recursive type S */ struct {
+	_ [unsafe.Sizeof(s)]byte
+}
+
+var s S
+
+// Since f is a pointer, this case could be valid.
+// But it's pathological and not worth the expense.
+type T struct {
+	f *[unsafe.Sizeof(T /* ERROR invalid recursive type */ {})]int
+}
+
+// a mutually recursive case using unsafe.Sizeof
+type (
+	A1 struct {
+		_ [unsafe.Sizeof(B1{})]int
+	}
+
+	B1 struct {
+		_ [unsafe.Sizeof(A1 /* ERROR invalid recursive type */ {})]int
+	}
+)
+
+// a mutually recursive case using len
+type (
+	A2 struct {
+		f [len(B2{}.f)]int
+	}
+
+	B2 struct {
+		f [len(A2 /* ERROR invalid recursive type */ {}.f)]int
+	}
+)
+
+// test case from issue
+type a struct {
+	_ [42 - unsafe.Sizeof(a /* ERROR invalid recursive type */ {})]byte
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue49296.go b/src/internal/types/testdata/fixedbugs/issue49296.go
new file mode 100644
index 0000000..98ad6f5
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49296.go
@@ -0,0 +1,20 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[
+        T0 any,
+        T1 []int,
+        T2 ~float64 | ~complex128 | chan int,
+]() {
+        _ = T0(nil /* ERROR cannot convert nil to type T0 */ )
+        _ = T1(1 /* ERROR cannot convert 1 .* to type T1 */ )
+        _ = T2(2 /* ERROR cannot convert 2 .* to type T2 */ )
+}
+
+// test case from issue
+func f[T interface{[]int}]() {
+	_ = T(1 /* ERROR cannot convert */ )
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue49439.go b/src/internal/types/testdata/fixedbugs/issue49439.go
new file mode 100644
index 0000000..b8ad495
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49439.go
@@ -0,0 +1,26 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "unsafe"
+
+type T0 /* ERROR invalid recursive type */ [P T0[P]] struct{}
+
+type T1 /* ERROR invalid recursive type */ [P T2[P]] struct{}
+type T2[P T1[P]] struct{}
+
+type T3 /* ERROR invalid recursive type */ [P interface{ ~struct{ f T3[int] } }] struct{}
+
+// valid cycle in M
+type N[P M[P]] struct{}
+type M[Q any] struct { F *M[Q] }
+
+// "crazy" case
+type TC[P [unsafe.Sizeof(func() {
+        type T [P [unsafe.Sizeof(func(){})]byte] struct{}
+})]byte] struct{}
+
+// test case from issue
+type X /* ERROR invalid recursive type */ [T any, PT X[T]] interface{}
diff --git a/src/internal/types/testdata/fixedbugs/issue49482.go b/src/internal/types/testdata/fixedbugs/issue49482.go
new file mode 100644
index 0000000..2b9e748
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49482.go
@@ -0,0 +1,26 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// The following is OK, per the special handling for type literals discussed in issue #49482.
+type _[P *struct{}] struct{}
+type _[P *int,] int
+type _[P (*int),] int
+
+const P = 2 // declare P to avoid noisy 'undefined' errors below.
+
+// The following parse as invalid array types due to parsing ambiguitiues.
+type _ [P *int /* ERROR "int \(type\) is not an expression" */ ]int
+type _ [P /* ERROR non-function P */ (*int)]int
+
+// Adding a trailing comma or an enclosing interface resolves the ambiguity.
+type _[P *int,] int
+type _[P (*int),] int
+type _[P interface{*int}] int
+type _[P interface{(*int)}] int
+
+// The following parse correctly as valid generic types.
+type _[P *struct{} | int] struct{}
+type _[P *struct{} | ~int] struct{}
diff --git a/src/internal/types/testdata/fixedbugs/issue49541.go b/src/internal/types/testdata/fixedbugs/issue49541.go
new file mode 100644
index 0000000..c8499c1
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49541.go
@@ -0,0 +1,45 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type S[A, B any] struct {
+	f int
+}
+
+func (S[A, B]) m() {}
+
+// TODO(gri): with type-type inference enabled we should only report one error
+// below. See issue #50588.
+
+func _[A any](s S /* ERROR got 1 arguments but 2 type parameters */ [A]) {
+	// we should see no follow-on errors below
+	s.f = 1
+	s.m()
+}
+
+// another test case from the issue
+
+func _() {
+	X(Interface[*F /* ERROR got 1 arguments but 2 type parameters */ [string]](Impl{}))
+}
+
+func X[Q Qer](fs Interface[Q]) {
+}
+
+type Impl struct{}
+
+func (Impl) M() {}
+
+type Interface[Q Qer] interface {
+	M()
+}
+
+type Qer interface {
+	Q()
+}
+
+type F[A, B any] struct{}
+
+func (f *F[A, B]) Q() {}
diff --git a/src/internal/types/testdata/fixedbugs/issue49579.go b/src/internal/types/testdata/fixedbugs/issue49579.go
new file mode 100644
index 0000000..ee2d94a
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49579.go
@@ -0,0 +1,17 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type I[F any] interface {
+	Q(*F)
+}
+
+func G[F any]() I[any] {
+	return g /* ERROR cannot use g\[F\]{} .* as I\[any\] value in return statement: g\[F\] does not implement I\[any\] \(method Q has pointer receiver\) */ [F]{}
+}
+
+type g[F any] struct{}
+
+func (*g[F]) Q(*any) {}
diff --git a/src/internal/types/testdata/fixedbugs/issue49592.go b/src/internal/types/testdata/fixedbugs/issue49592.go
new file mode 100644
index 0000000..846deaa
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49592.go
@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _() {
+	var x *interface{}
+	var y interface{}
+	_ = x == y
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue49602.go b/src/internal/types/testdata/fixedbugs/issue49602.go
new file mode 100644
index 0000000..208501f
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49602.go
@@ -0,0 +1,19 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type M interface {
+	m()
+}
+
+type C interface {
+	comparable
+}
+
+type _ interface {
+	int | M          // ERROR cannot use p\.M in union \(p\.M contains methods\)
+	int | comparable // ERROR cannot use comparable in union
+	int | C          // ERROR cannot use p\.C in union \(p\.C embeds comparable\)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue49705.go b/src/internal/types/testdata/fixedbugs/issue49705.go
new file mode 100644
index 0000000..5b5fba2
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49705.go
@@ -0,0 +1,14 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type Integer interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+	~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr
+}
+
+func shl[I Integer](n int) I {
+	return 1 << n
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue49735.go b/src/internal/types/testdata/fixedbugs/issue49735.go
new file mode 100644
index 0000000..5087022
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49735.go
@@ -0,0 +1,11 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[P1 any, P2 ~byte](s1 P1, s2 P2) {
+        _ = append(nil /* ERROR first argument to append must be a slice; have untyped nil */ , 0)
+        _ = append(s1 /* ERROR s1 .* has no core type */ , 0)
+        _ = append(s2 /* ERROR s2 .* has core type byte */ , 0)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue49739.go b/src/internal/types/testdata/fixedbugs/issue49739.go
new file mode 100644
index 0000000..7feb563
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49739.go
@@ -0,0 +1,23 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Verify that we get an empty type set (not just an error)
+// when using an invalid ~A.
+
+package p
+
+type A int
+type C interface {
+	~ /* ERROR invalid use of ~ */ A
+}
+
+func f[_ C]()              {}
+func g[_ interface{ C }]() {}
+func h[_ C | int]()        {}
+
+func _() {
+	_ = f[int /* ERROR cannot satisfy C \(empty type set\) */]
+	_ = g[int /* ERROR cannot satisfy interface{C} \(empty type set\) */]
+	_ = h[int]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue49864.go b/src/internal/types/testdata/fixedbugs/issue49864.go
new file mode 100644
index 0000000..0437e74
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue49864.go
@@ -0,0 +1,9 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[P ~int, Q any](p P) {
+	_ = Q(p /* ERROR cannot convert */ )
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50259.go b/src/internal/types/testdata/fixedbugs/issue50259.go
new file mode 100644
index 0000000..6df8c64
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50259.go
@@ -0,0 +1,18 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+var x T[B]
+
+type T[_ any] struct{}
+type A T[B]
+type B = T[A]
+
+// test case from issue
+
+var v Box[Step]
+type Box[T any] struct{}
+type Step = Box[StepBox]
+type StepBox Box[Step]
diff --git a/src/internal/types/testdata/fixedbugs/issue50276.go b/src/internal/types/testdata/fixedbugs/issue50276.go
new file mode 100644
index 0000000..97e477e
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50276.go
@@ -0,0 +1,39 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// simplified test case
+
+type transform[T any] struct{}
+type pair[S any] struct {}
+
+var _ transform[step]
+
+type box transform[step]
+type step = pair[box]
+
+// test case from issue
+
+type Transform[T any] struct{ hold T }
+type Pair[S, T any] struct {
+	First  S
+	Second T
+}
+
+var first Transform[Step]
+
+// This line doesn't use the Step alias, and it compiles fine if you uncomment it.
+var second Transform[Pair[Box, interface{}]]
+
+type Box *Transform[Step]
+
+// This line is the same as the `first` line, but it comes after the Box declaration and
+// does not break the compile.
+var third Transform[Step]
+
+type Step = Pair[Box, interface{}]
+
+// This line also does not break the compile
+var fourth Transform[Step]
diff --git a/src/internal/types/testdata/fixedbugs/issue50281.go b/src/internal/types/testdata/fixedbugs/issue50281.go
new file mode 100644
index 0000000..f333e81
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50281.go
@@ -0,0 +1,26 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[S string | []byte](s S) {
+	var buf []byte
+	_ = append(buf, s...)
+}
+
+func _[S ~string | ~[]byte](s S) {
+	var buf []byte
+	_ = append(buf, s...)
+}
+
+// test case from issue
+
+type byteseq interface {
+	string | []byte
+}
+
+// This should allow to eliminate the two functions above.
+func AppendByteString[source byteseq](buf []byte, s source) []byte {
+	return append(buf, s[1:6]...)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50321.go b/src/internal/types/testdata/fixedbugs/issue50321.go
new file mode 100644
index 0000000..199e66e
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50321.go
@@ -0,0 +1,8 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func Ln[A A /* ERROR cannot use a type parameter as constraint */ ](p A) {
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50372.go b/src/internal/types/testdata/fixedbugs/issue50372.go
new file mode 100644
index 0000000..4c9b65a
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50372.go
@@ -0,0 +1,27 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _(s []int) {
+        var i, j, k, l int
+        _, _, _, _ = i, j, k, l
+
+        for range s {}
+        for i = range s {}
+        for i, j = range s {}
+        for i, j, k /* ERROR range clause permits at most two iteration variables|at most 2 expressions */ = range s {}
+        for i, j, k, l /* ERROR range clause permits at most two iteration variables|at most 2 expressions */ = range s {}
+}
+
+func _(s chan int) {
+        var i, j, k, l int
+        _, _, _, _ = i, j, k, l
+
+        for range s {}
+        for i = range s {}
+        for i, j /* ERROR range over .* permits only one iteration variable */ = range s {}
+        for i, j, k /* ERROR range over .* permits only one iteration variable|at most 2 expressions */ = range s {}
+        for i, j, k, l /* ERROR range over .* permits only one iteration variable|at most 2 expressions */ = range s {}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50417.go b/src/internal/types/testdata/fixedbugs/issue50417.go
new file mode 100644
index 0000000..69ebf31
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50417.go
@@ -0,0 +1,68 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Field accesses through type parameters are disabled
+// until we have a more thorough understanding of the
+// implications on the spec. See issue #51576.
+
+package p
+
+type Sf struct {
+        f int
+}
+
+func f0[P Sf](p P) {
+        _ = p.f // ERROR p\.f undefined
+        p.f /* ERROR p\.f undefined */ = 0
+}
+
+func f0t[P ~struct{f int}](p P) {
+        _ = p.f // ERROR p\.f undefined
+        p.f /* ERROR p\.f undefined */ = 0
+}
+
+var _ = f0[Sf]
+var _ = f0t[Sf]
+
+var _ = f0[Sm /* ERROR does not satisfy */ ]
+var _ = f0t[Sm /* ERROR does not satisfy */ ]
+
+func f1[P interface{ Sf; m() }](p P) {
+        _ = p.f // ERROR p\.f undefined
+        p.f /* ERROR p\.f undefined */ = 0
+        p.m()
+}
+
+var _ = f1[Sf /* ERROR missing method m */ ]
+var _ = f1[Sm /* ERROR does not satisfy */ ]
+
+type Sm struct {}
+
+func (Sm) m() {}
+
+type Sfm struct {
+        f int
+}
+
+func (Sfm) m() {}
+
+func f2[P interface{ Sfm; m() }](p P) {
+        _ = p.f // ERROR p\.f undefined
+        p.f /* ERROR p\.f undefined */ = 0
+        p.m()
+}
+
+var _ = f2[Sfm]
+
+// special case: core type is a named pointer type
+
+type PSfm *Sfm
+
+func f3[P interface{ PSfm }](p P) {
+        _ = p.f // ERROR p\.f undefined
+        p.f /* ERROR p\.f undefined */ = 0
+        p.m /* ERROR type P has no field or method m */ ()
+}
+
+var _ = f3[PSfm]
diff --git a/src/internal/types/testdata/fixedbugs/issue50426.go b/src/internal/types/testdata/fixedbugs/issue50426.go
new file mode 100644
index 0000000..17ec0ce
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50426.go
@@ -0,0 +1,44 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type A1 [2]uint64
+type A2 [2]uint64
+
+func (a A1) m() A1 { return a }
+func (a A2) m() A2 { return a }
+
+func f[B any, T interface {
+	A1 | A2
+	m() T
+}](v T) {
+}
+
+func _() {
+	var v A2
+	// Use function type inference to infer type A2 for T.
+	// Don't use constraint type inference before function
+	// type inference for typed arguments, otherwise it would
+	// infer type [2]uint64 for T which doesn't have method m
+	// (was the bug).
+	f[int](v)
+}
+
+// Keep using constraint type inference before function type
+// inference for untyped arguments so we infer type float64
+// for E below, and not int (which would not work).
+func g[S ~[]E, E any](S, E) {}
+
+func _() {
+	var s []float64
+	g[[]float64](s, 0)
+}
+
+// Keep using constraint type inference after function
+// type inference for untyped arguments so we infer
+// missing type arguments for which we only have the
+// untyped arguments as starting point.
+func h[E any, R []E](v E) R { return R{v} }
+func _() []int              { return h(0) }
diff --git a/src/internal/types/testdata/fixedbugs/issue50427.go b/src/internal/types/testdata/fixedbugs/issue50427.go
new file mode 100644
index 0000000..d89d63e
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50427.go
@@ -0,0 +1,23 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// The parser no longer parses type parameters for methods.
+// In the past, type checking the code below led to a crash (#50427).
+
+type T interface{ m[ /* ERROR "must have no type parameters" */ P any]() }
+
+func _(t T) {
+	var _ interface{ m[ /* ERROR "must have no type parameters" */ P any](); n() } = t /* ERROR "does not implement" */
+}
+
+type S struct{}
+
+func (S) m[ /* ERROR "must have no type parameters" */ P any]() {}
+
+func _(s S) {
+	var _ interface{ m[ /* ERROR "must have no type parameters" */ P any](); n() } = s /* ERROR "does not implement" */
+
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50450.go b/src/internal/types/testdata/fixedbugs/issue50450.go
new file mode 100644
index 0000000..bae3111
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50450.go
@@ -0,0 +1,11 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type S struct{}
+
+func f[P S]() {}
+
+var _ = f[S]
diff --git a/src/internal/types/testdata/fixedbugs/issue50516.go b/src/internal/types/testdata/fixedbugs/issue50516.go
new file mode 100644
index 0000000..f73015e
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50516.go
@@ -0,0 +1,13 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[P struct{ f int }](x P) {
+	_ = x.g // ERROR type P has no field or method g
+}
+
+func _[P struct{ f int } | struct{ g int }](x P) {
+	_ = x.g // ERROR type P has no field or method g
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50646.go b/src/internal/types/testdata/fixedbugs/issue50646.go
new file mode 100644
index 0000000..ed7261c
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50646.go
@@ -0,0 +1,28 @@
+// -oldComparableSemantics
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f1[_ comparable]()              {}
+func f2[_ interface{ comparable }]() {}
+
+type T interface{ m() }
+
+func _[P comparable, Q ~int, R any]() {
+	_ = f1[int]
+	_ = f1[T /* ERROR T does not satisfy comparable */ ]
+	_ = f1[any /* ERROR any does not satisfy comparable */ ]
+	_ = f1[P]
+	_ = f1[Q]
+	_ = f1[R /* ERROR R does not satisfy comparable */]
+
+	_ = f2[int]
+	_ = f2[T /* ERROR T does not satisfy comparable */ ]
+	_ = f2[any /* ERROR any does not satisfy comparable */ ]
+	_ = f2[P]
+	_ = f2[Q]
+	_ = f2[R /* ERROR R does not satisfy comparable */]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50729.go b/src/internal/types/testdata/fixedbugs/issue50729.go
new file mode 100644
index 0000000..fe19fdf
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50729.go
@@ -0,0 +1,19 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// version 1
+var x1 T1[B1]
+
+type T1[_ any] struct{}
+type A1 T1[B1]
+type B1 = T1[A1]
+
+// version 2
+type T2[_ any] struct{}
+type A2 T2[B2]
+type B2 = T2[A2]
+
+var x2 T2[B2]
diff --git a/src/internal/types/testdata/fixedbugs/issue50755.go b/src/internal/types/testdata/fixedbugs/issue50755.go
new file mode 100644
index 0000000..afc7b24
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50755.go
@@ -0,0 +1,47 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// The core type of M2 unifies with the type of m1
+// during function argument type inference.
+// M2's constraint is unnamed.
+func f1[K1 comparable, E1 any](m1 map[K1]E1) {}
+
+func f2[M2 map[string]int](m2 M2) {
+	f1(m2)
+}
+
+// The core type of M3 unifies with the type of m1
+// during function argument type inference.
+// M3's constraint is named.
+type Map3 map[string]int
+
+func f3[M3 Map3](m3 M3) {
+	f1(m3)
+}
+
+// The core type of M5 unifies with the core type of M4
+// during constraint type inference.
+func f4[M4 map[K4]int, K4 comparable](m4 M4) {}
+
+func f5[M5 map[K5]int, K5 comparable](m5 M5) {
+	f4(m5)
+}
+
+// test case from issue
+
+func Copy[MC ~map[KC]VC, KC comparable, VC any](dst, src MC) {
+	for k, v := range src {
+		dst[k] = v
+	}
+}
+
+func Merge[MM ~map[KM]VM, KM comparable, VM any](ms ...MM) MM {
+	result := MM{}
+	for _, m := range ms {
+		Copy(result, m)
+	}
+	return result
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50779.go b/src/internal/types/testdata/fixedbugs/issue50779.go
new file mode 100644
index 0000000..fe68c28
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50779.go
@@ -0,0 +1,23 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type AC interface {
+	C
+}
+
+type ST []int
+
+type R[S any, P any] struct{}
+
+type SR = R[SS, ST]
+
+type SS interface {
+	NSR(any) *SR // ERROR invalid use of type alias SR in recursive type
+}
+
+type C interface {
+	NSR(any) *SR
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50782.go b/src/internal/types/testdata/fixedbugs/issue50782.go
new file mode 100644
index 0000000..0e7b712
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50782.go
@@ -0,0 +1,47 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Field accesses through type parameters are disabled
+// until we have a more thorough understanding of the
+// implications on the spec. See issue #51576.
+
+package p
+
+// The first example from the issue.
+type Numeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64
+}
+
+// numericAbs matches numeric types with an Abs method.
+type numericAbs[T Numeric] interface {
+	~struct{ Value T }
+	Abs() T
+}
+
+// AbsDifference computes the absolute value of the difference of
+// a and b, where the absolute value is determined by the Abs method.
+func absDifference[T numericAbs[T /* ERROR T does not satisfy Numeric */]](a, b T) T {
+	// Field accesses are not permitted for now. Keep an error so
+	// we can find and fix this code once the situation changes.
+	return a.Value // ERROR a\.Value undefined
+	// TODO: The error below should probably be positioned on the '-'.
+	// d := a /* ERROR "invalid operation: operator - not defined" */ .Value - b.Value
+	// return d.Abs()
+}
+
+// The second example from the issue.
+type T[P int] struct{ f P }
+
+func _[P T[P /* ERROR "P does not satisfy int" */ ]]() {}
+
+// Additional tests
+func _[P T[T /* ERROR "T\[P\] does not satisfy int" */ [P /* ERROR "P does not satisfy int" */ ]]]() {}
+func _[P T[Q /* ERROR "Q does not satisfy int" */ ], Q T[P /* ERROR "P does not satisfy int" */ ]]() {}
+func _[P T[Q], Q int]() {}
+
+type C[P comparable] struct{ f P }
+func _[P C[C[P]]]() {}
+func _[P C[C /* ERROR "C\[Q\] does not satisfy comparable" */ [Q /* ERROR "Q does not satisfy comparable" */]], Q func()]() {}
+func _[P [10]C[P]]() {}
+func _[P struct{ f C[C[P]]}]() {}
diff --git a/src/internal/types/testdata/fixedbugs/issue50816.go b/src/internal/types/testdata/fixedbugs/issue50816.go
new file mode 100644
index 0000000..e7e31d9
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50816.go
@@ -0,0 +1,23 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package pkg
+
+type I interface {
+	Foo()
+}
+
+type T1 struct{}
+
+func (T1) foo() {}
+
+type T2 struct{}
+
+func (T2) foo() string { return "" }
+
+func _() {
+	var i I
+	_ = i /* ERROR impossible type assertion: i\.\(T1\)\n\tT1 does not implement I \(missing method Foo\)\n\t\thave foo\(\)\n\t\twant Foo\(\) */ .(T1)
+	_ = i /* ERROR impossible type assertion: i\.\(T2\)\n\tT2 does not implement I \(missing method Foo\)\n\t\thave foo\(\) string\n\t\twant Foo\(\) */ .(T2)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50833.go b/src/internal/types/testdata/fixedbugs/issue50833.go
new file mode 100644
index 0000000..e912e4d
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50833.go
@@ -0,0 +1,16 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type (
+	S  struct{ f int }
+	PS *S
+)
+
+func a() []*S { return []*S{{f: 1}} }
+func b() []PS { return []PS{{f: 1}} }
+
+func c[P *S]() []P { return []P{{f: 1}} }
+func d[P PS]() []P { return []P{{f: 1}} }
diff --git a/src/internal/types/testdata/fixedbugs/issue50912.go b/src/internal/types/testdata/fixedbugs/issue50912.go
new file mode 100644
index 0000000..f161925
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50912.go
@@ -0,0 +1,19 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func Real[P ~complex128](x P) {
+	_ = real(x /* ERROR not supported */ )
+}
+
+func Imag[P ~complex128](x P) {
+	_ = imag(x /* ERROR not supported */ )
+}
+
+func Complex[P ~float64](x P) {
+	_ = complex(x /* ERROR not supported */ , 0)
+	_ = complex(0 /* ERROR not supported */ , x)
+	_ = complex(x /* ERROR not supported */ , x)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50918.go b/src/internal/types/testdata/fixedbugs/issue50918.go
new file mode 100644
index 0000000..41604b8
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50918.go
@@ -0,0 +1,21 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type thing1 struct {
+	things []string
+}
+
+type thing2 struct {
+	things []thing1
+}
+
+func _() {
+	var a1, b1 thing1
+	_ = a1 /* ERROR struct containing \[\]string cannot be compared */ == b1
+
+	var a2, b2 thing2
+	_ = a2 /* ERROR struct containing \[\]thing1 cannot be compared */ == b2
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50929.go b/src/internal/types/testdata/fixedbugs/issue50929.go
new file mode 100644
index 0000000..45e0751
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50929.go
@@ -0,0 +1,68 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file is tested when running "go test -run Manual"
+// without source arguments. Use for one-off debugging.
+
+package p
+
+import "fmt"
+
+type F[A, B any] int
+
+func G[A, B any](F[A, B]) {
+}
+
+func _() {
+	// TODO(gri) only report one error below (issue #50932)
+	var x F /* ERROR got 1 arguments but 2 type parameters */ [int]
+	G(x /* ERROR does not match */)
+}
+
+// test case from issue
+// (lots of errors but doesn't crash anymore)
+
+type RC[G any, RG any] interface {
+	~[]RG
+}
+
+type RG[G any] struct{}
+
+type RSC[G any] []*RG[G]
+
+type M[Rc RC[G, RG], G any, RG any] struct {
+	Fn func(Rc)
+}
+
+type NFn[Rc RC[G, RG], G any, RG any] func(Rc)
+
+func NC[Rc RC[G, RG], G any, RG any](nFn NFn[Rc, G, RG]) {
+	var empty Rc
+	nFn(empty)
+}
+
+func NSG[G any](c RSC[G]) {
+	fmt.Println(c)
+}
+
+func MMD[Rc RC /* ERROR got 1 arguments */ [RG], RG any, G any]() M /* ERROR got 2 arguments */ [Rc, RG] {
+
+	var nFn NFn /* ERROR got 2 arguments */ [Rc, RG]
+
+	var empty Rc
+	switch any(empty).(type) {
+	case BC /* ERROR undefined: BC */ :
+
+	case RSC[G]:
+		nFn = NSG /* ERROR cannot use NSG\[G\] */ [G]
+	}
+
+	return M /* ERROR got 2 arguments */ [Rc, RG]{
+		Fn: func(rc Rc) {
+			NC(nFn /* ERROR does not match */ )
+		},
+	}
+
+	return M /* ERROR got 2 arguments */ [Rc, RG]{}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue50965.go b/src/internal/types/testdata/fixedbugs/issue50965.go
new file mode 100644
index 0000000..bf2dcc9
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue50965.go
@@ -0,0 +1,17 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _(x int, c string) {
+	switch x {
+	case c /* ERROR invalid case c in switch on x \(mismatched types string and int\) */ :
+	}
+}
+
+func _(x, c []int) {
+	switch x {
+	case c /* ERROR invalid case c in switch on x \(slice can only be compared to nil\) */ :
+	}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51025.go b/src/internal/types/testdata/fixedbugs/issue51025.go
new file mode 100644
index 0000000..207b06e
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51025.go
@@ -0,0 +1,38 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+var _ interface{ m() } = struct /* ERROR m is a field, not a method */ {
+	m func()
+}{}
+
+var _ interface{ m() } = & /* ERROR m is a field, not a method */ struct {
+	m func()
+}{}
+
+var _ interface{ M() } = struct /* ERROR missing method M */ {
+	m func()
+}{}
+
+var _ interface{ M() } = & /* ERROR missing method M */ struct {
+	m func()
+}{}
+
+// test case from issue
+type I interface{ m() }
+type T struct{ m func() }
+type M struct{}
+
+func (M) m() {}
+
+func _() {
+	var t T
+	var m M
+	var i I
+
+	i = m
+	i = t // ERROR m is a field, not a method
+	_ = i
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51048.go b/src/internal/types/testdata/fixedbugs/issue51048.go
new file mode 100644
index 0000000..5830837
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51048.go
@@ -0,0 +1,11 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[P int]() {
+	_ = f[P]
+}
+
+func f[T int]() {}
diff --git a/src/internal/types/testdata/fixedbugs/issue51145.go b/src/internal/types/testdata/fixedbugs/issue51145.go
new file mode 100644
index 0000000..b84391d
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51145.go
@@ -0,0 +1,18 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "fmt"
+
+type (
+	_ [fmt /* ERROR invalid array length fmt */ ]int
+	_ [float64 /* ERROR invalid array length float64 */ ]int
+	_ [f /* ERROR invalid array length f */ ]int
+	_ [nil /* ERROR invalid array length nil */ ]int
+)
+
+func f()
+
+var _ fmt.Stringer // use fmt
diff --git a/src/internal/types/testdata/fixedbugs/issue51158.go b/src/internal/types/testdata/fixedbugs/issue51158.go
new file mode 100644
index 0000000..3edc505
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51158.go
@@ -0,0 +1,18 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// Type checking the following code should not cause an infinite recursion.
+func f[M map[K]int, K comparable](m M) {
+        f(m)
+}
+
+// Equivalent code using mutual recursion.
+func f1[M map[K]int, K comparable](m M) {
+        f2(m)
+}
+func f2[M map[K]int, K comparable](m M) {
+        f1(m)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51229.go b/src/internal/types/testdata/fixedbugs/issue51229.go
new file mode 100644
index 0000000..808b647
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51229.go
@@ -0,0 +1,164 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// Constraint type inference should be independent of the
+// ordering of the type parameter declarations. Try all
+// permutations in the test case below.
+// Permutations produced by https://go.dev/play/p/PHcZNGJTEBZ.
+
+func f00[S1 ~[]E1, S2 ~[]E2, E1 ~byte, E2 ~byte](S1, S2) {}
+func f01[S2 ~[]E2, S1 ~[]E1, E1 ~byte, E2 ~byte](S1, S2) {}
+func f02[E1 ~byte, S1 ~[]E1, S2 ~[]E2, E2 ~byte](S1, S2) {}
+func f03[S1 ~[]E1, E1 ~byte, S2 ~[]E2, E2 ~byte](S1, S2) {}
+func f04[S2 ~[]E2, E1 ~byte, S1 ~[]E1, E2 ~byte](S1, S2) {}
+func f05[E1 ~byte, S2 ~[]E2, S1 ~[]E1, E2 ~byte](S1, S2) {}
+func f06[E2 ~byte, S2 ~[]E2, S1 ~[]E1, E1 ~byte](S1, S2) {}
+func f07[S2 ~[]E2, E2 ~byte, S1 ~[]E1, E1 ~byte](S1, S2) {}
+func f08[S1 ~[]E1, E2 ~byte, S2 ~[]E2, E1 ~byte](S1, S2) {}
+func f09[E2 ~byte, S1 ~[]E1, S2 ~[]E2, E1 ~byte](S1, S2) {}
+func f10[S2 ~[]E2, S1 ~[]E1, E2 ~byte, E1 ~byte](S1, S2) {}
+func f11[S1 ~[]E1, S2 ~[]E2, E2 ~byte, E1 ~byte](S1, S2) {}
+func f12[S1 ~[]E1, E1 ~byte, E2 ~byte, S2 ~[]E2](S1, S2) {}
+func f13[E1 ~byte, S1 ~[]E1, E2 ~byte, S2 ~[]E2](S1, S2) {}
+func f14[E2 ~byte, S1 ~[]E1, E1 ~byte, S2 ~[]E2](S1, S2) {}
+func f15[S1 ~[]E1, E2 ~byte, E1 ~byte, S2 ~[]E2](S1, S2) {}
+func f16[E1 ~byte, E2 ~byte, S1 ~[]E1, S2 ~[]E2](S1, S2) {}
+func f17[E2 ~byte, E1 ~byte, S1 ~[]E1, S2 ~[]E2](S1, S2) {}
+func f18[E2 ~byte, E1 ~byte, S2 ~[]E2, S1 ~[]E1](S1, S2) {}
+func f19[E1 ~byte, E2 ~byte, S2 ~[]E2, S1 ~[]E1](S1, S2) {}
+func f20[S2 ~[]E2, E2 ~byte, E1 ~byte, S1 ~[]E1](S1, S2) {}
+func f21[E2 ~byte, S2 ~[]E2, E1 ~byte, S1 ~[]E1](S1, S2) {}
+func f22[E1 ~byte, S2 ~[]E2, E2 ~byte, S1 ~[]E1](S1, S2) {}
+func f23[S2 ~[]E2, E1 ~byte, E2 ~byte, S1 ~[]E1](S1, S2) {}
+
+type myByte byte
+
+func _(a []byte, b []myByte) {
+	f00(a, b)
+	f01(a, b)
+	f02(a, b)
+	f03(a, b)
+	f04(a, b)
+	f05(a, b)
+	f06(a, b)
+	f07(a, b)
+	f08(a, b)
+	f09(a, b)
+	f10(a, b)
+	f11(a, b)
+	f12(a, b)
+	f13(a, b)
+	f14(a, b)
+	f15(a, b)
+	f16(a, b)
+	f17(a, b)
+	f18(a, b)
+	f19(a, b)
+	f20(a, b)
+	f21(a, b)
+	f22(a, b)
+	f23(a, b)
+}
+
+// Constraint type inference may have to iterate.
+// Again, the order of the type parameters shouldn't matter.
+
+func g0[S ~[]E, M ~map[string]S, E any](m M) {}
+func g1[M ~map[string]S, S ~[]E, E any](m M) {}
+func g2[E any, S ~[]E, M ~map[string]S](m M) {}
+func g3[S ~[]E, E any, M ~map[string]S](m M) {}
+func g4[M ~map[string]S, E any, S ~[]E](m M) {}
+func g5[E any, M ~map[string]S, S ~[]E](m M) {}
+
+func _(m map[string][]byte) {
+	g0(m)
+	g1(m)
+	g2(m)
+	g3(m)
+	g4(m)
+	g5(m)
+}
+
+// Worst-case scenario.
+// There are 10 unknown type parameters. In each iteration of
+// constraint type inference we infer one more, from right to left.
+// Each iteration looks repeatedly at all 11 type parameters,
+// requiring a total of 10*11 = 110 iterations with the current
+// implementation. Pathological case.
+
+func h[K any, J ~*K, I ~*J, H ~*I, G ~*H, F ~*G, E ~*F, D ~*E, C ~*D, B ~*C, A ~*B](x A) {}
+
+func _(x **********int) {
+	h(x)
+}
+
+// Examples with channel constraints and tilde.
+
+func ch1[P chan<- int]() (_ P)           { return } // core(P) == chan<- int   (single type, no tilde)
+func ch2[P ~chan int]()                  { return } // core(P) == ~chan<- int  (tilde)
+func ch3[P chan E, E any](E)             { return } // core(P) == chan<- E     (single type, no tilde)
+func ch4[P chan E | ~chan<- E, E any](E) { return } // core(P) == ~chan<- E    (tilde)
+func ch5[P chan int | chan<- int]()      { return } // core(P) == chan<- int   (not a single type)
+
+func _() {
+	// P can be inferred as there's a single specific type and no tilde.
+	var _ chan int = ch1 /* ERROR cannot use ch1.*value of type chan<- int */ ()
+	var _ chan<- int = ch1()
+
+	// P cannot be inferred as there's a tilde.
+	ch2 /* ERROR cannot infer P */ ()
+	type myChan chan int
+	ch2[myChan]()
+
+	// P can be inferred as there's a single specific type and no tilde.
+	var e int
+	ch3(e)
+
+	// P cannot be inferred as there's more than one specific type and a tilde.
+	ch4 /* ERROR cannot infer P */ (e)
+	_ = ch4[chan int]
+
+	// P cannot be inferred as there's more than one specific type.
+	ch5 /* ERROR cannot infer P */ ()
+	ch5[chan<- int]()
+}
+
+// test case from issue
+
+func equal[M1 ~map[K1]V1, M2 ~map[K2]V2, K1, K2 ~uint32, V1, V2 ~string](m1 M1, m2 M2) bool {
+	if len(m1) != len(m2) {
+		return false
+	}
+	for k, v1 := range m1 {
+		if v2, ok := m2[K2(k)]; !ok || V2(v1) != v2 {
+			return false
+		}
+	}
+	return true
+}
+
+func equalFixed[K1, K2 ~uint32, V1, V2 ~string](m1 map[K1]V1, m2 map[K2]V2) bool {
+	if len(m1) != len(m2) {
+		return false
+	}
+	for k, v1 := range m1 {
+		if v2, ok := m2[K2(k)]; !ok || v1 != V1(v2) {
+			return false
+		}
+	}
+	return true
+}
+
+type (
+	someNumericID uint32
+	someStringID  string
+)
+
+func _() {
+	foo := map[uint32]string{10: "bar"}
+	bar := map[someNumericID]someStringID{10: "bar"}
+	equal(foo, bar)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51232.go b/src/internal/types/testdata/fixedbugs/issue51232.go
new file mode 100644
index 0000000..3fa6a05
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51232.go
@@ -0,0 +1,30 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type RC[RG any] interface {
+	~[]RG
+}
+
+type Fn[RCT RC[RG], RG any] func(RCT)
+
+type F[RCT RC[RG], RG any] interface {
+	Fn() Fn /* ERROR got 1 arguments */ [RCT]
+}
+
+type concreteF[RCT RC[RG], RG any] struct {
+	makeFn func() Fn /* ERROR got 1 arguments */ [RCT]
+}
+
+func (c *concreteF[RCT, RG]) Fn() Fn /* ERROR got 1 arguments */ [RCT] {
+	return c.makeFn()
+}
+
+func NewConcrete[RCT RC[RG], RG any](Rc RCT) F /* ERROR got 1 arguments */ [RCT] {
+	// TODO(rfindley): eliminate the duplicate error below.
+	return & /* ERROR cannot use .* as F\[RCT\] */ concreteF /* ERROR got 1 arguments */ [RCT]{
+		makeFn: nil,
+	}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51233.go b/src/internal/types/testdata/fixedbugs/issue51233.go
new file mode 100644
index 0000000..9c15028
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51233.go
@@ -0,0 +1,27 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// As of issue #51527, type-type inference has been disabled.
+
+type RC[RG any] interface {
+	~[]RG
+}
+
+type Fn[RCT RC[RG], RG any] func(RCT)
+
+type FFn[RCT RC[RG], RG any] func() Fn /* ERROR got 1 arguments */ [RCT]
+
+type F[RCT RC[RG], RG any] interface {
+	Fn() Fn /* ERROR got 1 arguments */ [RCT]
+}
+
+type concreteF[RCT RC[RG], RG any] struct {
+	makeFn FFn /* ERROR got 1 arguments */ [RCT]
+}
+
+func (c *concreteF[RCT, RG]) Fn() Fn /* ERROR got 1 arguments */ [RCT] {
+	return c.makeFn()
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51257.go b/src/internal/types/testdata/fixedbugs/issue51257.go
new file mode 100644
index 0000000..be4b81f
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51257.go
@@ -0,0 +1,48 @@
+// -oldComparableSemantics
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f[_ comparable]() {}
+
+type S1 struct{ x int }
+type S2 struct{ x any }
+type S3 struct{ x [10]interface{ m() } }
+
+func _[P1 comparable, P2 S2]() {
+	_ = f[S1]
+	_ = f[S2 /* ERROR S2 does not satisfy comparable */ ]
+	_ = f[S3 /* ERROR S3 does not satisfy comparable */ ]
+
+	type L1 struct { x P1 }
+	type L2 struct { x P2 }
+	_ = f[L1]
+	_ = f[L2 /* ERROR L2 does not satisfy comparable */ ]
+}
+
+
+// example from issue
+
+type Set[T comparable] map[T]struct{}
+
+func NewSetFromSlice[T comparable](items []T) *Set[T] {
+	s := Set[T]{}
+
+	for _, item := range items {
+		s[item] = struct{}{}
+	}
+
+	return &s
+}
+
+type T struct{ x any }
+
+func main() {
+	NewSetFromSlice /* ERROR T does not satisfy comparable */ ([]T{
+		{"foo"},
+		{5},
+	})
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51335.go b/src/internal/types/testdata/fixedbugs/issue51335.go
new file mode 100644
index 0000000..35135cd
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51335.go
@@ -0,0 +1,16 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type S1 struct{}
+type S2 struct{}
+
+func _[P *S1|*S2]() {
+	_= []P{{ /* ERROR invalid composite literal element type P \(no core type\) */ }}
+}
+
+func _[P *S1|S1]() {
+	_= []P{{ /* ERROR invalid composite literal element type P \(no core type\) */ }}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51339.go b/src/internal/types/testdata/fixedbugs/issue51339.go
new file mode 100644
index 0000000..38f8610
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51339.go
@@ -0,0 +1,18 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file is tested when running "go test -run Manual"
+// without source arguments. Use for one-off debugging.
+
+package p
+
+type T[P any, B *P] struct{}
+
+func (T /* ERROR cannot use generic type */ ) m0() {}
+
+// TODO(rfindley): eliminate the duplicate errors here.
+func (/* ERROR got 1 type parameter, but receiver base type declares 2 */ T /* ERROR got 1 arguments but 2 type parameters */ [_]) m1() {}
+func (T[_, _]) m2() {}
+// TODO(gri) this error is unfortunate (issue #51343)
+func (T /* ERROR got 3 arguments but 2 type parameters */ [_, _, _]) m3() {}
diff --git a/src/internal/types/testdata/fixedbugs/issue51360.go b/src/internal/types/testdata/fixedbugs/issue51360.go
new file mode 100644
index 0000000..fe3de04
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51360.go
@@ -0,0 +1,13 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _() {
+	len.Println /* ERROR cannot select on len */
+	len.Println /* ERROR cannot select on len */ ()
+	_ = len.Println /* ERROR cannot select on len */
+	_ = len /* ERROR cannot index len */ [0]
+	_ = *len /* ERROR cannot indirect len */
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51376.go b/src/internal/types/testdata/fixedbugs/issue51376.go
new file mode 100644
index 0000000..3801d68
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51376.go
@@ -0,0 +1,24 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type Map map[string]int
+
+func f[M ~map[K]V, K comparable, V any](M) {}
+func g[M map[K]V, K comparable, V any](M) {}
+
+func _[M1 ~map[K]V, M2 map[K]V, K comparable, V any]() {
+        var m1 M1
+        f(m1)
+        g /* ERROR M1 does not satisfy map\[K\]V */ (m1) // M1 has tilde
+
+        var m2 M2
+        f(m2)
+        g(m2) // M1 does not have tilde
+
+        var m3 Map
+        f(m3)
+        g /* ERROR Map does not satisfy map\[string\]int */ (m3) // M in g does not have tilde
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51386.go b/src/internal/types/testdata/fixedbugs/issue51386.go
new file mode 100644
index 0000000..ef62239
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51386.go
@@ -0,0 +1,17 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type myString string
+
+func _[P ~string | ~[]byte | ~[]rune]() {
+	_ = P("")
+	const s myString = ""
+	_ = P(s)
+}
+
+func _[P myString]() {
+	_ = P("")
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51437.go b/src/internal/types/testdata/fixedbugs/issue51437.go
new file mode 100644
index 0000000..3762615
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51437.go
@@ -0,0 +1,17 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T struct{}
+
+func (T) m() []int { return nil }
+
+func f(x T) {
+	for _, x := range func() []int {
+		return x.m() // x declared in parameter list of f
+	}() {
+		_ = x // x declared by range clause
+	}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51472.go b/src/internal/types/testdata/fixedbugs/issue51472.go
new file mode 100644
index 0000000..a0f9e9c
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51472.go
@@ -0,0 +1,54 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[T comparable](x T) {
+        _ = x == x
+}
+
+func _[T interface{interface{comparable}}](x T) {
+        _ = x == x
+}
+
+func _[T interface{comparable; interface{comparable}}](x T) {
+        _ = x == x
+}
+
+func _[T interface{comparable; ~int}](x T) {
+        _ = x == x
+}
+
+func _[T interface{comparable; ~[]byte}](x T) {
+        _ = x /* ERROR empty type set */ == x
+}
+
+// TODO(gri) The error message here should be better. See issue #51525.
+func _[T interface{comparable; ~int; ~string}](x T) {
+        _ = x /* ERROR empty type set */ == x
+}
+
+// TODO(gri) The error message here should be better. See issue #51525.
+func _[T interface{~int; ~string}](x T) {
+        _ = x /* ERROR empty type set */ == x
+}
+
+func _[T interface{comparable; interface{~int}; interface{int|float64}}](x T) {
+        _ = x == x
+}
+
+func _[T interface{interface{comparable; ~int}; interface{~float64; comparable; m()}}](x T) {
+        _ = x /* ERROR empty type set */ == x
+}
+
+// test case from issue
+
+func f[T interface{comparable; []byte|string}](x T) {
+        _ = x == x
+}
+
+func _(s []byte) {
+	f /* ERROR \[\]byte does not satisfy interface{comparable; \[\]byte \| string} */ (s)
+        _ = f[[ /* ERROR does not satisfy */ ]byte]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51509.go b/src/internal/types/testdata/fixedbugs/issue51509.go
new file mode 100644
index 0000000..64f5d7e
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51509.go
@@ -0,0 +1,7 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T /* ERROR invalid recursive type */ T.x
diff --git a/src/internal/types/testdata/fixedbugs/issue51525.go b/src/internal/types/testdata/fixedbugs/issue51525.go
new file mode 100644
index 0000000..5856905
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51525.go
@@ -0,0 +1,20 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[T interface {
+	int
+	string
+}](x T) {
+	_ = x /* ERROR empty type set */ == x
+	_ = x /* ERROR empty type set */ + x
+	<-x /* ERROR empty type set */
+	x <- /* ERROR empty type set */ 0
+	close(x /* ERROR empty type set */)
+}
+
+func _[T interface{ int | []byte }](x T) {
+	_ = x /* ERROR incomparable types in type set */ == x
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51533.go b/src/internal/types/testdata/fixedbugs/issue51533.go
new file mode 100644
index 0000000..bf46f75
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51533.go
@@ -0,0 +1,20 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _(x any) {
+	switch x {
+	case 0:
+		fallthrough // ERROR fallthrough statement out of place
+		_ = x
+	default:
+	}
+
+	switch x.(type) {
+	case int:
+		fallthrough // ERROR cannot fallthrough in type switch
+	default:
+	}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51578.go b/src/internal/types/testdata/fixedbugs/issue51578.go
new file mode 100644
index 0000000..5c204ba
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51578.go
@@ -0,0 +1,17 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+var _ = (*interface /* ERROR interface contains type constraints */ {int})(nil)
+
+// abbreviated test case from issue
+
+type TypeSet interface{ int | string }
+
+func _() {
+	f((*TypeSet /* ERROR interface contains type constraints */)(nil))
+}
+
+func f(any) {}
\ No newline at end of file
diff --git a/src/internal/types/testdata/fixedbugs/issue51593.go b/src/internal/types/testdata/fixedbugs/issue51593.go
new file mode 100644
index 0000000..e06c39f
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51593.go
@@ -0,0 +1,13 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f[P interface{ m(R) }, R any]() {}
+
+type T = interface { m(int) }
+
+func _() {
+	_ = f /* ERROR cannot infer R */ [T] // don't crash in type inference
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51607.go b/src/internal/types/testdata/fixedbugs/issue51607.go
new file mode 100644
index 0000000..d8df143
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51607.go
@@ -0,0 +1,65 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// Interface types must be ignored during overlap test.
+
+type (
+	T1 interface{int}
+	T2 interface{~int}
+	T3 interface{T1 | bool | string}
+	T4 interface{T2 | ~bool | ~string}
+)
+
+type (
+	// overlap errors for non-interface terms
+	// (like the interface terms, but explicitly inlined)
+	_ interface{int | int /* ERROR overlapping terms int and int */ }
+	_ interface{int | ~ /* ERROR overlapping terms ~int and int */ int}
+	_ interface{~int | int /* ERROR overlapping terms int and ~int */ }
+	_ interface{~int | ~ /* ERROR overlapping terms ~int and ~int */ int}
+
+	_ interface{T1 | bool | string | T1 | bool /* ERROR overlapping terms bool and bool */ | string /* ERROR overlapping terms string and string */ }
+	_ interface{T1 | bool | string | T2 | ~ /* ERROR overlapping terms ~bool and bool */ bool | ~ /* ERROR overlapping terms ~string and string */ string}
+
+	// no errors for interface terms
+	_ interface{T1 | T1}
+	_ interface{T1 | T2}
+	_ interface{T2 | T1}
+	_ interface{T2 | T2}
+
+	_ interface{T3 | T3 | int}
+	_ interface{T3 | T4 | bool }
+	_ interface{T4 | T3 | string }
+	_ interface{T4 | T4 | float64 }
+)
+
+func _[_ T1 | bool | string | T1 | bool /* ERROR overlapping terms */ ]() {}
+func _[_ T1 | bool | string | T2 | ~ /* ERROR overlapping terms */ bool ]() {}
+func _[_ T2 | ~bool | ~string | T1 | bool /* ERROR overlapping terms */ ]() {}
+func _[_ T2 | ~bool | ~string | T2 | ~ /* ERROR overlapping terms */ bool ]() {}
+
+func _[_ T3 | T3 | int]() {}
+func _[_ T3 | T4 | bool]() {}
+func _[_ T4 | T3 | string]() {}
+func _[_ T4 | T4 | float64]() {}
+
+// test cases from issue
+
+type _ interface {
+	interface {bool | int} | interface {bool | string}
+}
+
+type _ interface {
+	interface {bool | int} ; interface {bool | string}
+}
+
+type _ interface {
+	interface {bool; int} ; interface {bool; string}
+}
+
+type _ interface {
+	interface {bool; int} | interface {bool; string}
+}
\ No newline at end of file
diff --git a/src/internal/types/testdata/fixedbugs/issue51610.go b/src/internal/types/testdata/fixedbugs/issue51610.go
new file mode 100644
index 0000000..d10c788
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51610.go
@@ -0,0 +1,9 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _[P int | float64 | complex128]() {
+	_ = map[P]int{1: 1, 1.0 /* ERROR duplicate key 1 */ : 2, 1 /* ERROR duplicate key \(1 \+ 0i\) */ + 0i: 3}
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51616.go b/src/internal/types/testdata/fixedbugs/issue51616.go
new file mode 100644
index 0000000..e0efc9e
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51616.go
@@ -0,0 +1,19 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type (
+        C[T any] interface{~int; M() T}
+
+        _ C[bool]
+        _ comparable
+        _ interface {~[]byte | ~string}
+
+        // Alias type declarations may refer to "constraint" types
+        // like ordinary type declarations.
+        _ = C[bool]
+        _ = comparable
+        _ = interface {~[]byte | ~string}
+)
diff --git a/src/internal/types/testdata/fixedbugs/issue51658.go b/src/internal/types/testdata/fixedbugs/issue51658.go
new file mode 100644
index 0000000..f32051c
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51658.go
@@ -0,0 +1,43 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This test checks syntax errors which differ between
+// go/parser and the syntax package.
+// TODO: consolidate eventually
+
+package p
+
+type F { // ERROR expected type|type declaration
+	float64
+} // ERROR expected declaration|non-declaration statement
+
+func _[T F | int](x T) {
+	_ = x == 0 // don't crash when recording type of 0
+}
+
+// test case from issue
+
+type FloatType { // ERROR expected type|type declaration
+	float32 | float64
+} // ERROR expected declaration|non-declaration statement
+
+type IntegerType interface {
+	int8 | int16 | int32 | int64 | int |
+		uint8 | uint16 | uint32 | uint64 | uint
+}
+
+type ComplexType interface {
+	complex64 | complex128
+}
+
+type Number interface {
+	FloatType | IntegerType | ComplexType
+}
+
+func GetDefaultNumber[T Number](value, defaultValue T) T {
+	if value == 0 {
+		return defaultValue
+	}
+	return value
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue51877.go b/src/internal/types/testdata/fixedbugs/issue51877.go
new file mode 100644
index 0000000..c93242a
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue51877.go
@@ -0,0 +1,18 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type S struct {
+	f1 int
+	f2 bool
+}
+
+var (
+	_ = S{0}                    /* ERROR too few values in struct literal */
+	_ = struct{ f1, f2 int }{0} /* ERROR too few values in struct literal */
+
+	_ = S{0, true, "foo" /* ERROR too many values in struct literal */}
+	_ = struct{ f1, f2 int }{0, 1, 2 /* ERROR too many values in struct literal */}
+)
diff --git a/src/internal/types/testdata/fixedbugs/issue52031.go b/src/internal/types/testdata/fixedbugs/issue52031.go
new file mode 100644
index 0000000..448a550
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue52031.go
@@ -0,0 +1,33 @@
+// -lang=go1.12
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type resultFlags uint
+
+// Example from #52031.
+//
+// The following shifts should not produce errors on Go < 1.13, as their
+// untyped constant operands are representable by type uint.
+const (
+	_ resultFlags = (1 << iota) / 2
+
+	reportEqual
+	reportUnequal
+	reportByIgnore
+	reportByMethod
+	reportByFunc
+	reportByCycle
+)
+
+// Invalid cases.
+var x int = 1
+var _ = (8 << x /* ERROR "signed shift count .* requires go1.13 or later" */)
+
+const _ = (1 << 1.2 /* ERROR "truncated to uint" */)
+
+var y float64
+var _ = (1 << y /* ERROR "must be integer" */)
diff --git a/src/internal/types/testdata/fixedbugs/issue52401.go b/src/internal/types/testdata/fixedbugs/issue52401.go
new file mode 100644
index 0000000..c7efd8c
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue52401.go
@@ -0,0 +1,11 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _() {
+	const x = 0
+	x /* ERROR cannot assign to x */ += 1
+	x /* ERROR cannot assign to x */ ++
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue52529.go b/src/internal/types/testdata/fixedbugs/issue52529.go
new file mode 100644
index 0000000..de7b296
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue52529.go
@@ -0,0 +1,15 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type Foo[P any] struct {
+	_ *Bar[P]
+}
+
+type Bar[Q any] Foo[Q]
+
+func (v *Bar[R]) M() {
+	_ = (*Foo[R])(v)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue52698.go b/src/internal/types/testdata/fixedbugs/issue52698.go
new file mode 100644
index 0000000..ca794f8
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue52698.go
@@ -0,0 +1,62 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// correctness check: ensure that cycles through generic instantiations are detected
+type T[P any] struct {
+	_ P
+}
+
+type S /* ERROR invalid recursive type */ struct {
+	_ T[S]
+}
+
+// simplified test 1
+
+var _ A1[A1[string]]
+
+type A1[P any] struct {
+	_ B1[P]
+}
+
+type B1[P any] struct {
+	_ P
+}
+
+// simplified test 2
+var _ B2[A2]
+
+type A2 struct {
+	_ B2[string]
+}
+
+type B2[P any] struct {
+	_ C2[P]
+}
+
+type C2[P any] struct {
+	_ P
+}
+
+// test case from issue
+type T23 interface {
+	~struct {
+		Field0 T13[T15]
+	}
+}
+
+type T1[P1 interface {
+}] struct {
+	Field2 P1
+}
+
+type T13[P2 interface {
+}] struct {
+	Field2 T1[P2]
+}
+
+type T15 struct {
+	Field0 T13[string]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue52915.go b/src/internal/types/testdata/fixedbugs/issue52915.go
new file mode 100644
index 0000000..6c43386
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue52915.go
@@ -0,0 +1,23 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "unsafe"
+
+type T[P any] struct {
+	T /* ERROR   invalid recursive type */ [P]
+}
+
+func _[P any]() {
+	_ = unsafe.Sizeof(T[int]{})
+	_ = unsafe.Sizeof(struct{ T[int] }{})
+
+	_ = unsafe.Sizeof(T[P]{})
+	_ = unsafe.Sizeof(struct{ T[P] }{})
+}
+
+// TODO(gri) This is a follow-on error due to T[int] being invalid.
+//           We should try to avoid it.
+const _ = unsafe /* ERROR not constant */ .Sizeof(T[int]{})
diff --git a/src/internal/types/testdata/fixedbugs/issue53358.go b/src/internal/types/testdata/fixedbugs/issue53358.go
new file mode 100644
index 0000000..774136f
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue53358.go
@@ -0,0 +1,19 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type A struct{}
+
+func (*A) m() int { return 0 }
+
+var _ = A.m /* ERROR invalid method expression A\.m \(needs pointer receiver \(\*A\)\.m\) */ ()
+var _ = (*A).m(nil)
+
+type B struct{ A }
+
+var _ = B.m // ERROR invalid method expression B\.m \(needs pointer receiver \(\*B\)\.m\)
+var _ = (*B).m
+
+var _ = struct{ A }.m // ERROR invalid method expression struct{A}\.m \(needs pointer receiver \(\*struct{A}\)\.m\)
diff --git a/src/internal/types/testdata/fixedbugs/issue54280.go b/src/internal/types/testdata/fixedbugs/issue54280.go
new file mode 100644
index 0000000..e83e1a1
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue54280.go
@@ -0,0 +1,7 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+const C = 912_345_678_901_234_567_890_123_456_789_012_345_678_901_234_567_890_912_345_678_901_234_567_890_123_456_789_012_345_678_901_234_567_890_912_345_678_901_234_567_890_123_456_789_012_345_678_901_234_567_890_912 // ERROR constant overflow
diff --git a/src/internal/types/testdata/fixedbugs/issue54405.go b/src/internal/types/testdata/fixedbugs/issue54405.go
new file mode 100644
index 0000000..611d830
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue54405.go
@@ -0,0 +1,16 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test that we don't see spurious errors for ==
+// for values with invalid types due to prior errors.
+
+package p
+
+var x struct {
+	f *NotAType /* ERROR undefined */
+}
+var _ = x.f == nil // no error expected here
+
+var y *NotAType  /* ERROR undefined */
+var _ = y == nil // no error expected here
diff --git a/src/internal/types/testdata/fixedbugs/issue56351.go b/src/internal/types/testdata/fixedbugs/issue56351.go
new file mode 100644
index 0000000..d7d04b0
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue56351.go
@@ -0,0 +1,11 @@
+// -lang=go1.20
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _(s []int) {
+	clear /* ERROR clear requires go1\.21 or later */ (s)
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue56425.go b/src/internal/types/testdata/fixedbugs/issue56425.go
new file mode 100644
index 0000000..d85733f
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue56425.go
@@ -0,0 +1,8 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+const s float32 = 0
+var _ = 0 << s
diff --git a/src/internal/types/testdata/fixedbugs/issue56665.go b/src/internal/types/testdata/fixedbugs/issue56665.go
new file mode 100644
index 0000000..11786b9
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue56665.go
@@ -0,0 +1,30 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// Example from the issue:
+type A[T any] interface {
+	*T
+}
+
+type B[T any] interface {
+	B /* ERROR invalid recursive type */ [*T]
+}
+
+type C[T any, U B[U]] interface {
+	*T
+}
+
+// Simplified reproducer:
+type X[T any] interface {
+	X /* ERROR invalid recursive type */ [*T]
+}
+
+var _ X[int]
+
+// A related example that doesn't go through interfaces.
+type A2[P any] [10]A2 /* ERROR invalid recursive type */ [*P]
+
+var _ A2[int]
diff --git a/src/internal/types/testdata/fixedbugs/issue57155.go b/src/internal/types/testdata/fixedbugs/issue57155.go
new file mode 100644
index 0000000..ec9fb2b
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue57155.go
@@ -0,0 +1,14 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f[P *Q, Q any](p P, q Q) {
+	func() {
+		_ = f[P]
+		f(p, q)
+		f[P](p, q)
+		f[P, Q](p, q)
+	}()
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue57160.go b/src/internal/types/testdata/fixedbugs/issue57160.go
new file mode 100644
index 0000000..446d019
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue57160.go
@@ -0,0 +1,10 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _(x *int) {
+	_ = 0 < x // ERROR "invalid operation"
+	_ = x < 0 // ERROR "invalid operation"
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue57486.go b/src/internal/types/testdata/fixedbugs/issue57486.go
new file mode 100644
index 0000000..43ba1b0
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue57486.go
@@ -0,0 +1,29 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type C1 interface {
+	comparable
+}
+
+type C2 interface {
+	comparable
+	[2]any | int
+}
+
+func G1[T C1](t T) { _ = t == t }
+func G2[T C2](t T) { _ = t == t }
+
+func F1[V [2]any](v V) {
+	_ = G1[V /* ERROR "V does not satisfy comparable" */]
+	_ = G1[[2]any]
+	_ = G1[int]
+}
+
+func F2[V [2]any](v V) {
+	_ = G2[V /* ERROR "V does not satisfy C2" */]
+	_ = G2[[ /* ERROR "\[2\]any does not satisfy C2 \(C2 mentions \[2\]any, but \[2\]any is not in the type set of C2\)" */ 2]any]
+	_ = G2[int]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue57500.go b/src/internal/types/testdata/fixedbugs/issue57500.go
new file mode 100644
index 0000000..abdcb5e
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue57500.go
@@ -0,0 +1,16 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type C interface {
+	comparable
+	[2]any | int
+}
+
+func f[T C]() {}
+
+func _() {
+	_ = f[[ /* ERROR \[2\]any does not satisfy C \(C mentions \[2\]any, but \[2\]any is not in the type set of C\) */ 2]any]
+}
diff --git a/src/internal/types/testdata/fixedbugs/issue57522.go b/src/internal/types/testdata/fixedbugs/issue57522.go
new file mode 100644
index 0000000..d83e5b2
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue57522.go
@@ -0,0 +1,24 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// A simplified version of the code in the original report.
+type S[T any] struct{}
+var V = S[any]{}
+func (fs *S[T]) M(V.M /* ERROR "V.M is not a type" */) {}
+
+// Other minimal reproducers.
+type S1[T any] V1.M /* ERROR "V1.M is not a type" */
+type V1 = S1[any]
+
+type S2[T any] struct{}
+type V2 = S2[any]
+func (fs *S2[T]) M(x V2.M /* ERROR "V2.M is not a type" */ ) {}
+
+// The following still panics, as the selector is reached from check.expr
+// rather than check.typexpr. TODO(rfindley): fix this.
+// type X[T any] int
+// func (X[T]) M(x [X[int].M]int) {}
+
diff --git a/src/internal/types/testdata/fixedbugs/issue6977.go b/src/internal/types/testdata/fixedbugs/issue6977.go
new file mode 100644
index 0000000..8f4e9ba
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue6977.go
@@ -0,0 +1,82 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "io"
+
+// Alan's initial report.
+
+type I interface { f(); String() string }
+type J interface { g(); String() string }
+
+type IJ1 = interface { I; J }
+type IJ2 = interface { f(); g(); String() string }
+
+var _ = (*IJ1)(nil) == (*IJ2)(nil) // static assert that IJ1 and IJ2 are identical types
+
+// The canonical example.
+
+type ReadWriteCloser interface { io.ReadCloser; io.WriteCloser }
+
+// Some more cases.
+
+type M interface { m() }
+type M32 interface { m() int32 }
+type M64 interface { m() int64 }
+
+type U1 interface { m() }
+type U2 interface { m(); M }
+type U3 interface { M; m() }
+type U4 interface { M; M; M }
+type U5 interface { U1; U2; U3; U4 }
+
+type U6 interface { m(); m /* ERROR duplicate method */ () }
+type U7 interface { M32 /* ERROR duplicate method */ ; m() }
+type U8 interface { m(); M32 /* ERROR duplicate method */ }
+type U9 interface { M32; M64 /* ERROR duplicate method */ }
+
+// Verify that repeated embedding of the same interface(s)
+// eliminates duplicate methods early (rather than at the
+// end) to prevent exponential memory and time use.
+// Without early elimination, computing T29 may take dozens
+// of minutes.
+type (
+        T0 interface { m() }
+        T1 interface { T0; T0 }
+        T2 interface { T1; T1 }
+        T3 interface { T2; T2 }
+        T4 interface { T3; T3 }
+        T5 interface { T4; T4 }
+        T6 interface { T5; T5 }
+        T7 interface { T6; T6 }
+        T8 interface { T7; T7 }
+        T9 interface { T8; T8 }
+
+        T10 interface { T9; T9 }
+        T11 interface { T10; T10 }
+        T12 interface { T11; T11 }
+        T13 interface { T12; T12 }
+        T14 interface { T13; T13 }
+        T15 interface { T14; T14 }
+        T16 interface { T15; T15 }
+        T17 interface { T16; T16 }
+        T18 interface { T17; T17 }
+        T19 interface { T18; T18 }
+
+        T20 interface { T19; T19 }
+        T21 interface { T20; T20 }
+        T22 interface { T21; T21 }
+        T23 interface { T22; T22 }
+        T24 interface { T23; T23 }
+        T25 interface { T24; T24 }
+        T26 interface { T25; T25 }
+        T27 interface { T26; T26 }
+        T28 interface { T27; T27 }
+        T29 interface { T28; T28 }
+)
+
+// Verify that m is present.
+var x T29
+var _ = x.m
diff --git a/src/internal/types/testdata/spec/assignability.go b/src/internal/types/testdata/spec/assignability.go
new file mode 100644
index 0000000..0ab8eb3
--- /dev/null
+++ b/src/internal/types/testdata/spec/assignability.go
@@ -0,0 +1,264 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package assignability
+
+// See the end of this package for the declarations
+// of the types and variables used in these tests.
+
+// "x's type is identical to T"
+func _[TP any](X TP) {
+	b = b
+	a = a
+	l = l
+	s = s
+	p = p
+	f = f
+	i = i
+	m = m
+	c = c
+	d = d
+
+	B = B
+	A = A
+	L = L
+	S = S
+	P = P
+	F = F
+	I = I
+	M = M
+	C = C
+	D = D
+	X = X
+}
+
+// "x's type V and T have identical underlying types
+// and at least one of V or T is not a named type."
+// (here a named type is a type with a name)
+func _[TP1, TP2 Interface](X1 TP1, X2 TP2) {
+	b = B // ERROR cannot use B .* as int value
+	a = A
+	l = L
+	s = S
+	p = P
+	f = F
+	i = I
+	m = M
+	c = C
+	d = D
+
+	B = b // ERROR cannot use b .* as Basic value
+	A = a
+	L = l
+	S = s
+	P = p
+	F = f
+	I = i
+	M = m
+	C = c
+	D = d
+	X1 = i  // ERROR cannot use i .* as TP1 value
+	X1 = X2 // ERROR cannot use X2 .* as TP1 value
+}
+
+// "T is an interface type and x implements T and T is not a type parameter"
+func _[TP Interface](X TP) {
+	i = d // ERROR missing method m
+	i = D
+	i = X
+	X = i // ERROR cannot use i .* as TP value
+}
+
+// "x is a bidirectional channel value, T is a channel type, x's type V and T have identical element types, and at least one of V or T is not a named type"
+// (here a named type is a type with a name)
+type (
+	_SendChan = chan<- int
+	_RecvChan = <-chan int
+
+	SendChan _SendChan
+	RecvChan _RecvChan
+)
+
+func _[
+	_CC ~_Chan,
+	_SC ~_SendChan,
+	_RC ~_RecvChan,
+
+	CC Chan,
+	SC SendChan,
+	RC RecvChan,
+]() {
+	var (
+		_ _SendChan = c
+		_ _RecvChan = c
+		_ _Chan     = c
+
+		_ _SendChan = C
+		_ _RecvChan = C
+		_ _Chan     = C
+
+		_ SendChan = c
+		_ RecvChan = c
+		_ Chan     = c
+
+		_ SendChan = C // ERROR cannot use C .* as SendChan value
+		_ RecvChan = C // ERROR cannot use C .* as RecvChan value
+		_ Chan     = C
+		_ Chan     = make /* ERROR cannot use make\(chan Basic\) .* as Chan value */ (chan Basic)
+	)
+
+	var (
+		_ _CC = C // ERROR cannot use C .* as _CC value
+		_ _SC = C // ERROR cannot use C .* as _SC value
+		_ _RC = C // ERROR cannot use C .* as _RC value
+
+		_ CC = _CC /* ERROR cannot use _CC\(nil\) .* as CC value */ (nil)
+		_ SC = _CC /* ERROR cannot use _CC\(nil\) .* as SC value */ (nil)
+		_ RC = _CC /* ERROR cannot use _CC\(nil\) .* as RC value */ (nil)
+
+		_ CC = C // ERROR cannot use C .* as CC value
+		_ SC = C // ERROR cannot use C .* as SC value
+		_ RC = C // ERROR cannot use C .* as RC value
+	)
+}
+
+// "x's type V is not a named type and T is a type parameter, and x is assignable to each specific type in T's type set."
+func _[
+	TP0 any,
+	TP1 ~_Chan,
+	TP2 ~chan int | ~chan byte,
+]() {
+	var (
+		_ TP0 = c // ERROR cannot use c .* as TP0 value
+		_ TP0 = C // ERROR cannot use C .* as TP0 value
+		_ TP1 = c
+		_ TP1 = C // ERROR cannot use C .* as TP1 value
+		_ TP2 = c // ERROR .* cannot assign chan int to chan byte
+	)
+}
+
+// "x's type V is a type parameter and T is not a named type, and values x' of each specific type in V's type set are assignable to T."
+func _[
+	TP0 Interface,
+	TP1 ~_Chan,
+	TP2 ~chan int | ~chan byte,
+](X0 TP0, X1 TP1, X2 TP2) {
+	i = X0
+	I = X0
+	c = X1
+	C = X1 // ERROR cannot use X1 .* as Chan value
+	c = X2 // ERROR .* cannot assign chan byte \(in TP2\) to chan int
+}
+
+// "x is the predeclared identifier nil and T is a pointer, function, slice, map, channel, or interface type"
+func _[TP Interface](X TP) {
+	b = nil // ERROR cannot use nil
+	a = nil // ERROR cannot use nil
+	l = nil
+	s = nil // ERROR cannot use nil
+	p = nil
+	f = nil
+	i = nil
+	m = nil
+	c = nil
+	d = nil // ERROR cannot use nil
+
+	B = nil // ERROR cannot use nil
+	A = nil // ERROR cannot use nil
+	L = nil
+	S = nil // ERROR cannot use nil
+	P = nil
+	F = nil
+	I = nil
+	M = nil
+	C = nil
+	D = nil // ERROR cannot use nil
+	X = nil // ERROR cannot use nil
+}
+
+// "x is an untyped constant representable by a value of type T"
+func _[
+	Int8 ~int8,
+	Int16 ~int16,
+	Int32 ~int32,
+	Int64 ~int64,
+	Int8_16 ~int8 | ~int16,
+](
+	i8 Int8,
+	i16 Int16,
+	i32 Int32,
+	i64 Int64,
+	i8_16 Int8_16,
+) {
+	b = 42
+	b = 42.0
+	// etc.
+
+	i8 = -1 << 7
+	i8 = 1<<7 - 1
+	i16 = -1 << 15
+	i16 = 1<<15 - 1
+	i32 = -1 << 31
+	i32 = 1<<31 - 1
+	i64 = -1 << 63
+	i64 = 1<<63 - 1
+
+	i8_16 = -1 << 7
+	i8_16 = 1<<7 - 1
+	i8_16 = - /* ERROR cannot use .* as Int8_16 */ 1 << 15
+	i8_16 = 1 /* ERROR cannot use .* as Int8_16 */ <<15 - 1
+}
+
+// proto-types for tests
+
+type (
+	_Basic     = int
+	_Array     = [10]int
+	_Slice     = []int
+	_Struct    = struct{ f int }
+	_Pointer   = *int
+	_Func      = func(x int) string
+	_Interface = interface{ m() int }
+	_Map       = map[string]int
+	_Chan      = chan int
+
+	Basic     _Basic
+	Array     _Array
+	Slice     _Slice
+	Struct    _Struct
+	Pointer   _Pointer
+	Func      _Func
+	Interface _Interface
+	Map       _Map
+	Chan      _Chan
+	Defined   _Struct
+)
+
+func (Defined) m() int
+
+// proto-variables for tests
+
+var (
+	b _Basic
+	a _Array
+	l _Slice
+	s _Struct
+	p _Pointer
+	f _Func
+	i _Interface
+	m _Map
+	c _Chan
+	d _Struct
+
+	B Basic
+	A Array
+	L Slice
+	S Struct
+	P Pointer
+	F Func
+	I Interface
+	M Map
+	C Chan
+	D Defined
+)
diff --git a/src/internal/types/testdata/spec/comparable.go b/src/internal/types/testdata/spec/comparable.go
new file mode 100644
index 0000000..f407c35
--- /dev/null
+++ b/src/internal/types/testdata/spec/comparable.go
@@ -0,0 +1,26 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f1[_ comparable]()              {}
+func f2[_ interface{ comparable }]() {}
+
+type T interface{ m() }
+
+func _[P comparable, Q ~int, R any]() {
+	_ = f1[int]
+	_ = f1[T /* T does satisfy comparable */]
+	_ = f1[any /* any does satisfy comparable */]
+	_ = f1[P]
+	_ = f1[Q]
+	_ = f1[R /* ERROR R does not satisfy comparable */]
+
+	_ = f2[int]
+	_ = f2[T /* T does satisfy comparable */]
+	_ = f2[any /* any does satisfy comparable */]
+	_ = f2[P]
+	_ = f2[Q]
+	_ = f2[R /* ERROR R does not satisfy comparable */]
+}
diff --git a/src/internal/types/testdata/spec/comparable1.19.go b/src/internal/types/testdata/spec/comparable1.19.go
new file mode 100644
index 0000000..dc1c5fa
--- /dev/null
+++ b/src/internal/types/testdata/spec/comparable1.19.go
@@ -0,0 +1,28 @@
+// -lang=go1.19
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f1[_ comparable]()              {}
+func f2[_ interface{ comparable }]() {}
+
+type T interface{ m() }
+
+func _[P comparable, Q ~int, R any]() {
+	_ = f1[int]
+	_ = f1[T /* ERROR T to satisfy comparable requires go1\.20 or later */]
+	_ = f1[any /* ERROR any to satisfy comparable requires go1\.20 or later */]
+	_ = f1[P]
+	_ = f1[Q]
+	_ = f1[R /* ERROR R does not satisfy comparable */]
+
+	_ = f2[int]
+	_ = f2[T /* ERROR T to satisfy comparable requires go1\.20 or later */]
+	_ = f2[any /* ERROR any to satisfy comparable requires go1\.20 or later */]
+	_ = f2[P]
+	_ = f2[Q]
+	_ = f2[R /* ERROR R does not satisfy comparable */]
+}
diff --git a/src/internal/types/testdata/spec/comparisons.go b/src/internal/types/testdata/spec/comparisons.go
new file mode 100644
index 0000000..886e78c
--- /dev/null
+++ b/src/internal/types/testdata/spec/comparisons.go
@@ -0,0 +1,120 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package comparisons
+
+type (
+	B int // basic type representative
+	A [10]func()
+	L []byte
+	S struct{ f []byte }
+	P *S
+	F func()
+	I interface{}
+	M map[string]int
+	C chan int
+)
+
+var (
+	b B
+	a A
+	l L
+	s S
+	p P
+	f F
+	i I
+	m M
+	c C
+)
+
+func _() {
+	_ = nil == nil // ERROR operator == not defined on untyped nil
+	_ = b == b
+	_ = a /* ERROR \[10\]func\(\) cannot be compared */ == a
+	_ = l /* ERROR slice can only be compared to nil */ == l
+	_ = s /* ERROR struct containing \[\]byte cannot be compared */ == s
+	_ = p == p
+	_ = f /* ERROR func can only be compared to nil */ == f
+	_ = i == i
+	_ = m /* ERROR map can only be compared to nil */ == m
+	_ = c == c
+
+	_ = b == nil /* ERROR mismatched types */
+	_ = a == nil /* ERROR mismatched types */
+	_ = l == nil
+	_ = s == nil /* ERROR mismatched types */
+	_ = p == nil
+	_ = f == nil
+	_ = i == nil
+	_ = m == nil
+	_ = c == nil
+
+	_ = nil /* ERROR operator < not defined on untyped nil */ < nil
+	_ = b < b
+	_ = a /* ERROR operator < not defined on array */ < a
+	_ = l /* ERROR operator < not defined on slice */ < l
+	_ = s /* ERROR operator < not defined on struct */ < s
+	_ = p /* ERROR operator < not defined on pointer */ < p
+	_ = f /* ERROR operator < not defined on func */ < f
+	_ = i /* ERROR operator < not defined on interface */ < i
+	_ = m /* ERROR operator < not defined on map */ < m
+	_ = c /* ERROR operator < not defined on chan */ < c
+}
+
+func _[
+	B int,
+	A [10]func(),
+	L []byte,
+	S struct{ f []byte },
+	P *S,
+	F func(),
+	I interface{},
+	J comparable,
+	M map[string]int,
+	C chan int,
+](
+	b B,
+	a A,
+	l L,
+	s S,
+	p P,
+	f F,
+	i I,
+	j J,
+	m M,
+	c C,
+) {
+	_ = b == b
+	_ = a /* ERROR incomparable types in type set */ == a
+	_ = l /* ERROR incomparable types in type set */ == l
+	_ = s /* ERROR incomparable types in type set */ == s
+	_ = p == p
+	_ = f /* ERROR incomparable types in type set */ == f
+	_ = i /* ERROR incomparable types in type set */ == i
+	_ = j == j
+	_ = m /* ERROR incomparable types in type set */ == m
+	_ = c == c
+
+	_ = b == nil /* ERROR mismatched types */
+	_ = a == nil /* ERROR mismatched types */
+	_ = l == nil
+	_ = s == nil /* ERROR mismatched types */
+	_ = p == nil
+	_ = f == nil
+	_ = i == nil /* ERROR mismatched types */
+	_ = j == nil /* ERROR mismatched types */
+	_ = m == nil
+	_ = c == nil
+
+	_ = b < b
+	_ = a /* ERROR type parameter A is not comparable with < */ < a
+	_ = l /* ERROR type parameter L is not comparable with < */ < l
+	_ = s /* ERROR type parameter S is not comparable with < */ < s
+	_ = p /* ERROR type parameter P is not comparable with < */ < p
+	_ = f /* ERROR type parameter F is not comparable with < */ < f
+	_ = i /* ERROR type parameter I is not comparable with < */ < i
+	_ = j /* ERROR type parameter J is not comparable with < */ < j
+	_ = m /* ERROR type parameter M is not comparable with < */ < m
+	_ = c /* ERROR type parameter C is not comparable with < */ < c
+}
diff --git a/src/internal/types/testdata/spec/conversions.go b/src/internal/types/testdata/spec/conversions.go
new file mode 100644
index 0000000..fc014fc
--- /dev/null
+++ b/src/internal/types/testdata/spec/conversions.go
@@ -0,0 +1,208 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package conversions
+
+import "unsafe"
+
+// constant conversions
+
+func _[T ~byte]() T { return 255 }
+func _[T ~byte]() T { return 256 /* ERROR cannot use 256 .* as T value */ }
+
+func _[T ~byte]() {
+	const _ = T /* ERROR T\(0\) .* is not constant */ (0)
+	var _ T = 255
+	var _ T = 256 // ERROR cannot use 256 .* as T value
+}
+
+func _[T ~string]() T                { return T('a') }
+func _[T ~int | ~string]() T         { return T('a') }
+func _[T ~byte | ~int | ~string]() T { return T(256 /* ERROR cannot convert 256 .* to type T */) }
+
+// implicit conversions never convert to string
+func _[T ~string]() {
+	var _ string = 0 // ERROR cannot use .* as string value
+	var _ T = 0      // ERROR cannot use .* as T value
+}
+
+// failing const conversions of constants to type parameters report a cause
+func _[
+	T1 any,
+	T2 interface{ m() },
+	T3 ~int | ~float64 | ~bool,
+	T4 ~int | ~string,
+]() {
+	_ = T1(0 /* ERROR cannot convert 0 .* to type T1: T1 does not contain specific types */)
+	_ = T2(1 /* ERROR cannot convert 1 .* to type T2: T2 does not contain specific types */)
+	_ = T3(2 /* ERROR cannot convert 2 .* to type T3: cannot convert 2 .* to type bool \(in T3\) */)
+	_ = T4(3.14 /* ERROR cannot convert 3.14 .* to type T4: cannot convert 3.14 .* to type int \(in T4\) */)
+}
+
+// "x is assignable to T"
+// - tested via assignability tests
+
+// "x's type and T have identical underlying types if tags are ignored"
+
+func _[X ~int, T ~int](x X) T { return T(x) }
+func _[X struct {
+	f int "foo"
+}, T struct {
+	f int "bar"
+}](x X) T {
+	return T(x)
+}
+
+type Foo struct {
+	f int "foo"
+}
+type Bar struct {
+	f int "bar"
+}
+type Far struct{ f float64 }
+
+func _[X Foo, T Bar](x X) T       { return T(x) }
+func _[X Foo | Bar, T Bar](x X) T { return T(x) }
+func _[X Foo, T Foo | Bar](x X) T { return T(x) }
+func _[X Foo, T Far](x X) T {
+	return T(x /* ERROR cannot convert x \(variable of type X constrained by Foo\) to type T: cannot convert Foo \(in X\) to type Far \(in T\) */)
+}
+
+// "x's type and T are unnamed pointer types and their pointer base types
+// have identical underlying types if tags are ignored"
+
+func _[X ~*Foo, T ~*Bar](x X) T         { return T(x) }
+func _[X ~*Foo | ~*Bar, T ~*Bar](x X) T { return T(x) }
+func _[X ~*Foo, T ~*Foo | ~*Bar](x X) T { return T(x) }
+func _[X ~*Foo, T ~*Far](x X) T {
+	return T(x /* ERROR cannot convert x \(variable of type X constrained by ~\*Foo\) to type T: cannot convert \*Foo \(in X\) to type \*Far \(in T\) */)
+}
+
+// Verify that the defined types in constraints are considered for the rule above.
+
+type (
+	B  int
+	C  int
+	X0 *B
+	T0 *C
+)
+
+func _(x X0) T0           { return T0(x /* ERROR cannot convert */) } // non-generic reference
+func _[X X0, T T0](x X) T { return T(x /* ERROR cannot convert */) }
+func _[T T0](x X0) T      { return T(x /* ERROR cannot convert */) }
+func _[X X0](x X) T0      { return T0(x /* ERROR cannot convert */) }
+
+// "x's type and T are both integer or floating point types"
+
+func _[X Integer, T Integer](x X) T  { return T(x) }
+func _[X Unsigned, T Integer](x X) T { return T(x) }
+func _[X Float, T Integer](x X) T    { return T(x) }
+
+func _[X Integer, T Unsigned](x X) T  { return T(x) }
+func _[X Unsigned, T Unsigned](x X) T { return T(x) }
+func _[X Float, T Unsigned](x X) T    { return T(x) }
+
+func _[X Integer, T Float](x X) T  { return T(x) }
+func _[X Unsigned, T Float](x X) T { return T(x) }
+func _[X Float, T Float](x X) T    { return T(x) }
+
+func _[X, T Integer | Unsigned | Float](x X) T { return T(x) }
+func _[X, T Integer | ~string](x X) T {
+	return T(x /* ERROR cannot convert x \(variable of type X constrained by Integer \| ~string\) to type T: cannot convert string \(in X\) to type int \(in T\) */)
+}
+
+// "x's type and T are both complex types"
+
+func _[X, T Complex](x X) T { return T(x) }
+func _[X, T Float | Complex](x X) T {
+	return T(x /* ERROR cannot convert x \(variable of type X constrained by Float \| Complex\) to type T: cannot convert float32 \(in X\) to type complex64 \(in T\) */)
+}
+
+// "x is an integer or a slice of bytes or runes and T is a string type"
+
+type myInt int
+type myString string
+
+func _[T ~string](x int) T      { return T(x) }
+func _[T ~string](x myInt) T    { return T(x) }
+func _[X Integer](x X) string   { return string(x) }
+func _[X Integer](x X) myString { return myString(x) }
+func _[X Integer](x X) *string {
+	return (*string)(x /* ERROR cannot convert x \(variable of type X constrained by Integer\) to type \*string: cannot convert int \(in X\) to type \*string */)
+}
+
+func _[T ~string](x []byte) T                           { return T(x) }
+func _[T ~string](x []rune) T                           { return T(x) }
+func _[X ~[]byte, T ~string](x X) T                     { return T(x) }
+func _[X ~[]rune, T ~string](x X) T                     { return T(x) }
+func _[X Integer | ~[]byte | ~[]rune, T ~string](x X) T { return T(x) }
+func _[X Integer | ~[]byte | ~[]rune, T ~*string](x X) T {
+	return T(x /* ERROR cannot convert x \(variable of type X constrained by Integer \| ~\[\]byte \| ~\[\]rune\) to type T: cannot convert int \(in X\) to type \*string \(in T\) */)
+}
+
+// "x is a string and T is a slice of bytes or runes"
+
+func _[T ~[]byte](x string) T { return T(x) }
+func _[T ~[]rune](x string) T { return T(x) }
+func _[T ~[]rune](x *string) T {
+	return T(x /* ERROR cannot convert x \(variable of type \*string\) to type T: cannot convert \*string to type \[\]rune \(in T\) */)
+}
+
+func _[X ~string, T ~[]byte](x X) T           { return T(x) }
+func _[X ~string, T ~[]rune](x X) T           { return T(x) }
+func _[X ~string, T ~[]byte | ~[]rune](x X) T { return T(x) }
+func _[X ~*string, T ~[]byte | ~[]rune](x X) T {
+	return T(x /* ERROR cannot convert x \(variable of type X constrained by ~\*string\) to type T: cannot convert \*string \(in X\) to type \[\]byte \(in T\) */)
+}
+
+// package unsafe:
+// "any pointer or value of underlying type uintptr can be converted into a unsafe.Pointer"
+
+type myUintptr uintptr
+
+func _[X ~uintptr](x X) unsafe.Pointer  { return unsafe.Pointer(x) }
+func _[T unsafe.Pointer](x myUintptr) T { return T(x) }
+func _[T unsafe.Pointer](x int64) T {
+	return T(x /* ERROR cannot convert x \(variable of type int64\) to type T: cannot convert int64 to type unsafe\.Pointer \(in T\) */)
+}
+
+// "and vice versa"
+
+func _[T ~uintptr](x unsafe.Pointer) T  { return T(x) }
+func _[X unsafe.Pointer](x X) uintptr   { return uintptr(x) }
+func _[X unsafe.Pointer](x X) myUintptr { return myUintptr(x) }
+func _[X unsafe.Pointer](x X) int64 {
+	return int64(x /* ERROR cannot convert x \(variable of type X constrained by unsafe\.Pointer\) to type int64: cannot convert unsafe\.Pointer \(in X\) to type int64 */)
+}
+
+// "x is a slice, T is an array or pointer-to-array type,
+// and the slice and array types have identical element types."
+
+func _[X ~[]E, T ~[10]E, E any](x X) T  { return T(x) }
+func _[X ~[]E, T ~*[10]E, E any](x X) T { return T(x) }
+
+// ----------------------------------------------------------------------------
+// The following declarations can be replaced by the exported types of the
+// constraints package once all builders support importing interfaces with
+// type constraints.
+
+type Signed interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64
+}
+
+type Unsigned interface {
+	~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr
+}
+
+type Integer interface {
+	Signed | Unsigned
+}
+
+type Float interface {
+	~float32 | ~float64
+}
+
+type Complex interface {
+	~complex64 | ~complex128
+}
diff --git a/src/internal/types/testdata/spec/oldcomparable.go b/src/internal/types/testdata/spec/oldcomparable.go
new file mode 100644
index 0000000..081d972
--- /dev/null
+++ b/src/internal/types/testdata/spec/oldcomparable.go
@@ -0,0 +1,28 @@
+// -oldComparableSemantics
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func f1[_ comparable]()              {}
+func f2[_ interface{ comparable }]() {}
+
+type T interface{ m() }
+
+func _[P comparable, Q ~int, R any]() {
+	_ = f1[int]
+	_ = f1[T /* ERROR T does not satisfy comparable */]
+	_ = f1[any /* ERROR any does not satisfy comparable */]
+	_ = f1[P]
+	_ = f1[Q]
+	_ = f1[R /* ERROR R does not satisfy comparable */]
+
+	_ = f2[int]
+	_ = f2[T /* ERROR T does not satisfy comparable */]
+	_ = f2[any /* ERROR any does not satisfy comparable */]
+	_ = f2[P]
+	_ = f2[Q]
+	_ = f2[R /* ERROR R does not satisfy comparable */]
+}