Adding upstream version 1.18.10.upstream/1.18.10upstream

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

24 files changed, 1723 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/syntax/testdata/go2/chans.go2 b/src/cmd/compile/internal/syntax/testdata/go2/chans.go2
new file mode 100644
index 0000000..fad2bce
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/go2/chans.go2
@@ -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/cmd/compile/internal/syntax/testdata/go2/linalg.go2 b/src/cmd/compile/internal/syntax/testdata/go2/linalg.go2
new file mode 100644
index 0000000..822d028
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/go2/linalg.go2
@@ -0,0 +1,83 @@
+// 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
+
+import "math"
+
+// 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
+}
+
+// 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/cmd/compile/internal/syntax/testdata/go2/map.go2 b/src/cmd/compile/internal/syntax/testdata/go2/map.go2
new file mode 100644
index 0000000..814d953
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/go2/map.go2
@@ -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/cmd/compile/internal/syntax/testdata/go2/map2.go2 b/src/cmd/compile/internal/syntax/testdata/go2/map2.go2
new file mode 100644
index 0000000..2833445
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/go2/map2.go2
@@ -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])
+
+// 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
+}
\ No newline at end of file
diff --git a/src/cmd/compile/internal/syntax/testdata/go2/slices.go2 b/src/cmd/compile/internal/syntax/testdata/go2/slices.go2
new file mode 100644
index 0000000..2bacd1c
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/go2/slices.go2
@@ -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/cmd/compile/internal/syntax/testdata/go2/smoketest.go2 b/src/cmd/compile/internal/syntax/testdata/go2/smoketest.go2
new file mode 100644
index 0000000..42efb42
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/go2/smoketest.go2
@@ -0,0 +1,83 @@
+// 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 basic generic code snippets.
+
+package p
+
+// type parameter lists
+type B[P any] struct{}
+type _[P interface{}] struct{}
+type _[P B] struct{}
+type _[P B[P]] struct{}
+
+type _[A, B, C any] struct{}
+type _[A, B, C B] struct{}
+type _[A, B, C B[A, B, C]] struct{}
+type _[A1, A2 B1, A3 B2, A4, A5, A6 B3] struct{}
+
+type _[A interface{}] struct{}
+type _[A, B interface{ m() }] struct{}
+
+type _[A, B, C any] struct{}
+
+// in functions
+func _[P any]()
+func _[P interface{}]()
+func _[P B]()
+func _[P B[P]]()
+
+// in methods
+func (T) _[P any]()
+func (T) _[P interface{}]()
+func (T) _[P B]()
+func (T) _[P B[P]]()
+
+// type instantiations
+type _ T[int]
+
+// in expressions
+var _ = T[int]{}
+
+// in embedded types
+type _ struct{ T[int] }
+
+// interfaces
+type _ interface{
+	m()
+	~int
+}
+
+type _ interface{
+	~int | ~float | ~string
+	~complex128
+	underlying(underlying underlying) underlying
+}
+
+type _ interface{
+	T
+	T[int]
+}
+
+// tricky cases
+func _(T[P], T[P1, P2])
+func _(a [N]T)
+
+type _ struct{
+	T[P]
+	T[P1, P2]
+	f [N]
+}
+type _ interface{
+	m()
+
+	// generic methods - disabled for now
+	// m[] /* ERROR empty type parameter list */ ()
+	// m[ /* ERROR cannot have type parameters */ P any](P)
+
+	// instantiated types
+	// T[] /* ERROR empty type argument list */ 
+	T[P]
+	T[P1, P2]
+}
diff --git a/src/cmd/compile/internal/syntax/testdata/go2/typeinst.go2 b/src/cmd/compile/internal/syntax/testdata/go2/typeinst.go2
new file mode 100644
index 0000000..a422d5e
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/go2/typeinst.go2
@@ -0,0 +1,60 @@
+// 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
+
+type T1[P any] P
+
+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. Syntax error.
+// TODO(gri) Disabled for now as we don't check syntax error here.
+// type A1[P any] = /* ERROR cannot be alias */ P
+
+// But an alias may refer to a generic, uninstantiated type.
+type A2 = List
+var _ A2[int]
+var _ A2 /* ERROR without instantiation */
+
+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 */ [int]
+type _ myInt /* ERROR not a generic type */ [int]
+
+// TODO(gri) better error messages
+type _ T1[int]
+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 illegal cycle */ [P]
+type self2[P any] *self2[P] // this is ok
diff --git a/src/cmd/compile/internal/syntax/testdata/go2/typeinst2.go2 b/src/cmd/compile/internal/syntax/testdata/go2/typeinst2.go2
new file mode 100644
index 0000000..76b8d55
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/go2/typeinst2.go2
@@ -0,0 +1,232 @@
+// 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)
+
+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)
+
+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()
+}
+
+// Interface type constraints can contain any type, incl. *Named types.
+// Verify that we use the underlying type to compute the operational type.
+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 type constraints leads to interfaces
+// with type constraints that are the intersection of the embedded
+// type constraints.
+
+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 does not satisfy I012 */ ]
+var _ = f012[bool /* ERROR does not satisfy I012 */ ]
+var _ = f012[string /* ERROR does not satisfy I012 */ ]
+var _ = f012[float64 /* ERROR does not satisfy I012 */ ]
+
+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_ */ ]
diff --git a/src/cmd/compile/internal/syntax/testdata/go2/typeparams.go2 b/src/cmd/compile/internal/syntax/testdata/go2/typeparams.go2
new file mode 100644
index 0000000..111f7c1
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/go2/typeparams.go2
@@ -0,0 +1,451 @@
+// 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
+
+// The predeclared identifier "any" is only visible as a constraint
+// in a type parameter list.
+var _ any // ERROR undeclared
+func _[_ any /* ok here */ , _ interface{any /* ERROR undeclared */ }](any /* ERROR undeclared */ ) {
+        var _ any /* ERROR undeclared */
+}
+
+func identity[T any](x T) T { return x }
+
+func _[_ any](x int) int
+func _[T any](T /* ERROR redeclared */ T)()
+func _[T, T /* ERROR redeclared */ any]()
+
+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 convert 0 .* to \[\]chan int */ )
+
+func swap[A, B any](a A, b B) (B, A) { return b, a }
+
+var _ = swap /* ERROR single value is expected */ [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 cannot compare */ < y }
+func _[T interface{ ~int | ~float32 | ~bool }](x, y T) bool { return x /* ERROR cannot compare */ < y }
+
+func _[T C1[T]](x, y T) bool { return x /* ERROR cannot compare */ < 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}) int
+var _ = f1(int)(struct{T1}{})
+type T1 = int
+
+func f2[t1 any](struct{t1; x float32}) int
+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
+
+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[string]int }] (x T, i int) { _ = x[i] }
+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] }
+
+// slicing
+// TODO(gri) implement this
+
+func _[T interface{ ~string }] (x T, i, j, k int) { _ = x /* ERROR invalid operation */ [i:j:k] }
+
+// 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 */ {}
+}
+
+func _[T interface{ ~string | ~[]string }](x T) {
+        for range x {}
+        for i := range x { _ = i }
+        for i, _ := range x { _ = i }
+        for i, e := range x /* ERROR must have the same element type */ { _ = i }
+        for _, e := range x /* ERROR must have the same element type */ {}
+        var e rune
+        _ = e
+        for _, (e) = range x /* ERROR must have the same element type */ {}
+}
+
+
+func _[T interface{ ~string | ~[]rune | ~map[int]rune }](x T) {
+        for _, e := range x { _ = e }
+        for i, e := range x { _ = i; _ = e }
+}
+
+func _[T interface{ ~string | ~[]rune | ~map[string]rune }](x T) {
+        for _, e := range x { _ = e }
+        for i, e := range x /* ERROR must have the same key type */ { _ = e }
+}
+
+func _[T interface{ ~string | ~chan int }](x T) {
+        for range x {}
+        for i := range x { _ = i }
+        for i, _ := range x { _ = i } // TODO(gri) should get an error here: channels only return one value
+}
+
+func _[T interface{ ~string | ~chan<-int }](x T) {
+        for i := range x /* ERROR send-only channel */ { _ = i }
+}
+
+// type inference checks
+
+var _ = new() /* ERROR cannot infer T */
+
+func f4[A, B, C any](A, B) C
+
+var _ = f4(1, 2) /* ERROR cannot infer C */
+var _ = f4[int, float32, complex128](1, 2)
+
+func f5[A, B, C any](A, []*B, struct{f []C}) int
+
+var _ = f5[int, float32, complex128](0, nil, struct{f []complex128}{})
+var _ = f5(0, nil, struct{f []complex128}{}) // ERROR cannot infer
+var _ = f5(0, []*float32{new[float32]()}, struct{f []complex128}{})
+
+func f6[A any](A, []A) int
+
+var _ = f6(0, nil)
+
+func f6nil[A any](A) int
+
+var _ = f6nil(nil) // ERROR cannot infer
+
+// type inference with variadic functions
+
+func f7[T any](...T) T
+
+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
+
+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[/* ERROR func init must have no type parameters */ P any]() {}
+
+type T struct {}
+
+func (T) m1() {}
+// The type checker accepts method type parameters if configured accordingly.
+func (T) m2[_ any]() {}
+func (T) m3[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
+
+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 parameters in methods (generalization)
+
+type R0 struct{}
+
+func (R0) _[T any](x T)
+func (R0 /* ERROR invalid receiver */ ) _[R0 any]() // scope of type parameters starts at "func"
+
+type R1[A, B any] struct{}
+
+func (_ R1[A, B]) m0(A, B)
+func (_ R1[A, B]) m1[T any](A, B, T) T
+func (_ R1 /* ERROR not a generic type */ [R1, _]) _()
+func (_ R1[A, B]) _[A /* ERROR redeclared */ any](B)
+
+func _() {
+        var r R1[int, string]
+        r.m1[rune](42, "foo", 'a')
+        r.m1[rune](42, "foo", 1.2 /* ERROR truncated to rune */)
+        r.m1(42, "foo", 1.2) // using type inference
+        var _ float64 = r.m1(42, "foo", 1.2)
+}
+
+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 not an interface */ .(int)
+	switch x /* ERROR not an interface */ .(type) {
+	}
+
+	// work-around
+	var t interface{} = x
+	_ = t.(int)
+	switch t.(type) {
+	}
+}
+
+func _[T interface{ ~int }](x T) {
+	_ = x /* ERROR not an interface */ .(int)
+	switch x /* ERROR not an interface */ .(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 interface I has no method m */ ()
+}
+
+func _[P interface{}] (x P) {
+	x.m /* ERROR type bound for P has no method m */ ()
+}
+
+func _[P any] (x P) {
+	x.m /* ERROR type bound for P has no method m */ ()
+}
+
+// automatic distinguishing between array and generic types
+// NOTE: Disabled when using unified parameter list syntax.
+/*
+const P = 10
+type A1 [P]byte
+func _(a A1) {
+        assert(len(a) == 10)
+}
+
+type A2 [P]struct{
+        f [P]byte
+}
+func _(a A2) {
+        assert(len(a) == 10)
+        assert(len(a[0].f) == 10)
+}
+
+type A3 [P]func(x [P]A3)
+func _(a A3) {
+        assert(len(a) == 10)
+}
+
+type T2[P] struct{ P }
+var _ T2[int]
+
+type T3[P] func(P)
+var _ T3[int]
+*/
\ No newline at end of file
diff --git a/src/cmd/compile/internal/syntax/testdata/interface.go2 b/src/cmd/compile/internal/syntax/testdata/interface.go2
new file mode 100644
index 0000000..dbc4187
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/interface.go2
@@ -0,0 +1,74 @@
+// 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 contains test cases for interfaces containing
+// constraint elements.
+
+package p
+
+type _ interface {
+	m()
+	E
+}
+
+type _ interface {
+	m()
+	~int
+	int | string
+	int | ~string
+	~int | ~string
+}
+
+type _ interface {
+	m()
+	~int
+	T[int, string] | string
+	int | ~T[string, struct{}]
+	~int | ~string
+}
+
+type _ interface {
+	int
+	[]byte
+	[10]int
+	struct{}
+	*int
+	func()
+	interface{}
+	map[string]int
+	chan T
+	chan<- T
+	<-chan T
+	T[int]
+}
+
+type _ interface {
+	int | string
+	[]byte | string
+	[10]int | string
+	struct{} | string
+	*int | string
+	func() | string
+	interface{} | string
+	map[string]int | string
+	chan T | string
+	chan<- T | string
+	<-chan T | string
+	T[int] | string
+}
+
+type _ interface {
+	~int | string
+	~[]byte | string
+	~[10]int | string
+	~struct{} | string
+	~*int | string
+	~func() | string
+	~interface{} | string
+	~map[string]int | string
+	~chan T | string
+	~chan<- T | string
+	~<-chan T | string
+	~T[int] | string
+}
diff --git a/src/cmd/compile/internal/syntax/testdata/issue20789.src b/src/cmd/compile/internal/syntax/testdata/issue20789.src
new file mode 100644
index 0000000..5f150db
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/issue20789.src
@@ -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.
+
+// Make sure this doesn't crash the compiler.
+// Line 9 must end in EOF for this test (no newline).
+
+package e
+func([<-chan<-[func /* ERROR unexpected u */ u){go /* ERROR must be function call */
\ No newline at end of file
diff --git a/src/cmd/compile/internal/syntax/testdata/issue23385.src b/src/cmd/compile/internal/syntax/testdata/issue23385.src
new file mode 100644
index 0000000..2459a73
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/issue23385.src
@@ -0,0 +1,17 @@
+// 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.
+
+// Check error message for use of = instead of == .
+
+package p
+
+func _() {
+	if true || 0 /* ERROR cannot use assignment .* as value */ = 1 {
+	}
+}
+
+func _(a, b string) {
+	if a == "a" && b /* ERROR cannot use assignment .* as value */ = "b" {
+	}
+}
diff --git a/src/cmd/compile/internal/syntax/testdata/issue23434.src b/src/cmd/compile/internal/syntax/testdata/issue23434.src
new file mode 100644
index 0000000..5a72a7f
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/issue23434.src
@@ -0,0 +1,31 @@
+// 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.
+
+// Test case for issue 23434: Better synchronization of
+// parser after missing type. There should be exactly
+// one error each time, with now follow errors.
+
+package p
+
+type T /* ERROR unexpected newline */
+
+type Map map[int] /* ERROR unexpected newline */
+
+// Examples from #23434:
+
+func g() {
+	m := make(map[string] /* ERROR unexpected ! */ !)
+	for {
+		x := 1
+		print(x)
+	}
+}
+
+func f() {
+	m := make(map[string] /* ERROR unexpected \) */ )
+	for {
+		x := 1
+		print(x)
+	}
+}
diff --git a/src/cmd/compile/internal/syntax/testdata/issue31092.src b/src/cmd/compile/internal/syntax/testdata/issue31092.src
new file mode 100644
index 0000000..b1839b8
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/issue31092.src
@@ -0,0 +1,16 @@
+// 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.
+
+// Test cases for issue 31092: Better synchronization of
+// parser after seeing an := rather than an = in a const,
+// type, or variable declaration.
+
+package p
+
+const _ /* ERROR unexpected := */ := 0
+type _ /* ERROR unexpected := */ := int
+var _ /* ERROR unexpected := */ := 0
+
+const _ int /* ERROR unexpected := */ := 0
+var _ int /* ERROR unexpected := */ := 0
diff --git a/src/cmd/compile/internal/syntax/testdata/issue43527.go2 b/src/cmd/compile/internal/syntax/testdata/issue43527.go2
new file mode 100644
index 0000000..dd2c9b1
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/issue43527.go2
@@ -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.
+
+package p
+
+type (
+        // 0 and 1-element []-lists are syntactically valid
+        _[A, B /* ERROR missing type constraint */ ] int
+        _[A, /* ERROR type parameters must be named */ interface{}] int
+        _[A, B, C /* ERROR missing type constraint */ ] int
+        _[A B, C /* ERROR missing type constraint */ ] int
+        _[A B, /* ERROR type parameters must be named */ interface{}] int
+        _[A B, /* ERROR type parameters must be named */ interface{}, C D] int
+        _[A B, /* ERROR type parameters must be named */ interface{}, C, D] int
+        _[A B, /* ERROR type parameters must be named */ interface{}, C, interface{}] int
+        _[A B, C interface{}, D, /* ERROR type parameters must be named */ interface{}] int
+)
+
+// function type parameters use the same parsing routine - just have a couple of tests
+
+func _[A, B /* ERROR missing type constraint */ ]() {}
+func _[A, /* ERROR type parameters must be named */ interface{}]() {}
diff --git a/src/cmd/compile/internal/syntax/testdata/issue43674.src b/src/cmd/compile/internal/syntax/testdata/issue43674.src
new file mode 100644
index 0000000..51c692a
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/issue43674.src
@@ -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 _(... /* ERROR [.][.][.] is missing type */ )
+func _(... /* ERROR [.][.][.] is missing type */ , int)
+
+func _(a, b ... /* ERROR [.][.][.] is missing type */ )
+func _(a, b ... /* ERROR [.][.][.] is missing type */ , x int)
+
+func _()(... /* ERROR [.][.][.] is missing type */ )
diff --git a/src/cmd/compile/internal/syntax/testdata/issue46558.src b/src/cmd/compile/internal/syntax/testdata/issue46558.src
new file mode 100644
index 0000000..a22b600
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/issue46558.src
@@ -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 F(s string) {
+	switch s[0] {
+	case 'a':
+		case s[2] { // ERROR unexpected {
+		case 'b':
+		}
+	}
+} // ERROR non-declaration statement
diff --git a/src/cmd/compile/internal/syntax/testdata/issue47704.go2 b/src/cmd/compile/internal/syntax/testdata/issue47704.go2
new file mode 100644
index 0000000..4e65857
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/issue47704.go2
@@ -0,0 +1,18 @@
+// 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
+
+// error messages for parser in generic mode
+func _() {
+	_ = m[] // ERROR expecting operand
+	_ = m[x,]
+	_ = m[x /* ERROR unexpected a */ a b c d]
+}
+
+// test case from the issue
+func f(m map[int]int) int {
+	return m[0 // ERROR expecting comma, \: or \]
+		]
+}
diff --git a/src/cmd/compile/internal/syntax/testdata/issue47704.src b/src/cmd/compile/internal/syntax/testdata/issue47704.src
new file mode 100644
index 0000000..0156af7
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/issue47704.src
@@ -0,0 +1,18 @@
+// 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
+
+// error messages for parser in non-generic mode
+func _() {
+	_ = m[]   // ERROR expecting operand
+	_ = m[x,] // ERROR unexpected comma, expecting \: or \]
+	_ = m[x /* ERROR unexpected a */ a b c d]
+}
+
+// test case from the issue
+func f(m map[int]int) int {
+	return m[0 // ERROR expecting \: or \]
+		]
+}
diff --git a/src/cmd/compile/internal/syntax/testdata/issue48382.go2 b/src/cmd/compile/internal/syntax/testdata/issue48382.go2
new file mode 100644
index 0000000..c00fee6
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/issue48382.go2
@@ -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 _ func /* ERROR function type must have no type parameters */ [ /* ERROR empty type parameter list */ ]()
+type _ func /* ERROR function type must have no type parameters */ [ x /* ERROR missing type constraint */ ]()
+type _ func /* ERROR function type must have no type parameters */ [P any]()
+
+var _ = func /* ERROR function literal must have no type parameters */ [P any]() {}
+
+type _ interface{
+        m /* ERROR interface method must have no type parameters */ [P any]()
+}
diff --git a/src/cmd/compile/internal/syntax/testdata/issue49482.go2 b/src/cmd/compile/internal/syntax/testdata/issue49482.go2
new file mode 100644
index 0000000..1fc303d
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/issue49482.go2
@@ -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 (
+        // these need a comma to disambiguate
+        _[P *T,] struct{}
+        _[P *T, _ any] struct{}
+        _[P (*T),] struct{}
+        _[P (*T), _ any] struct{}
+        _[P (T),] struct{}
+        _[P (T), _ any] struct{}
+
+        // these parse as name followed by type
+        _[P *struct{}] struct{}
+        _[P (*struct{})] struct{}
+        _[P ([]int)] struct{}
+
+        // array declarations
+        _ [P(T)]struct{}
+        _ [P((T))]struct{}
+        _ [P * *T] struct{} // this could be a name followed by a type but it makes the rules more complicated
+        _ [P * T]struct{}
+        _ [P(*T)]struct{}
+        _ [P(**T)]struct{}
+        _ [P * T - T]struct{}
+        _ [P*T-T /* ERROR unexpected comma */ ,]struct{}
+        _ [10 /* ERROR unexpected comma */ ,]struct{}
+)
diff --git a/src/cmd/compile/internal/syntax/testdata/sample.src b/src/cmd/compile/internal/syntax/testdata/sample.src
new file mode 100644
index 0000000..5a2b4bf
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/sample.src
@@ -0,0 +1,33 @@
+// 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 is a sample test file illustrating the use
+// of error comments with the error test harness.
+
+package p
+
+// The following are invalid error comments; they are
+// silently ignored. The prefix must be exactly one of
+// "/* ERROR " or "// ERROR ".
+//
+/*ERROR*/
+/*ERROR foo*/
+/* ERRORfoo */
+/*  ERROR foo */
+//ERROR
+// ERROR
+// ERRORfoo
+//  ERROR foo
+
+// This is a valid error comment; it applies to the
+// immediately following token. 
+import "math" /* ERROR unexpected comma */ ,
+
+// If there are multiple /*-style error comments before
+// the next token, only the last one is considered.
+type x = /* ERROR ignored */ /* ERROR literal 0 in type declaration */ 0
+
+// A //-style error comment matches any error position
+// on the same line.
+func () foo() // ERROR method has no receiver
diff --git a/src/cmd/compile/internal/syntax/testdata/tparams.go2 b/src/cmd/compile/internal/syntax/testdata/tparams.go2
new file mode 100644
index 0000000..a9bd72c
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/tparams.go2
@@ -0,0 +1,24 @@
+// 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[a, b /* ERROR missing type constraint */ ] struct{}
+type t[a t, b t, c /* ERROR missing type constraint */ ] struct{}
+type t struct {
+	t [n]byte
+	t[a]
+	t[a, b]
+}
+type t interface {
+	t[a]
+	m /* ERROR method must have no type parameters */ [_ _, /* ERROR mixed */ _]()
+	t[a, b]
+}
+
+func f[ /* ERROR empty type parameter list */ ]()
+func f[a, b /* ERROR missing type constraint */ ]()
+func f[a t, b t, c /* ERROR missing type constraint */ ]()
+
+func f[a b,  /* ERROR expecting ] */ 0] ()
diff --git a/src/cmd/compile/internal/syntax/testdata/typeset.go2 b/src/cmd/compile/internal/syntax/testdata/typeset.go2
new file mode 100644
index 0000000..19b74f2
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/typeset.go2
@@ -0,0 +1,89 @@
+// 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 contains test cases for typeset-only constraint elements.
+
+package p
+
+type (
+        _[_ t] t
+        _[_ ~t] t
+        _[_ t|t] t
+        _[_ ~t|t] t
+        _[_ t|~t] t
+        _[_ ~t|~t] t
+
+        _[_ t, _, _ t|t] t
+        _[_ t, _, _ ~t|t] t
+        _[_ t, _, _ t|~t] t
+        _[_ t, _, _ ~t|~t] t
+
+        _[_ t.t] t
+        _[_ ~t.t] t
+        _[_ t.t|t.t] t
+        _[_ ~t.t|t.t] t
+        _[_ t.t|~t.t] t
+        _[_ ~t.t|~t.t] t
+
+        _[_ t, _, _ t.t|t.t] t
+        _[_ t, _, _ ~t.t|t.t] t
+        _[_ t, _, _ t.t|~t.t] t
+        _[_ t, _, _ ~t.t|~t.t] t
+
+        _[_ struct{}] t
+        _[_ ~struct{}] t
+
+        _[_ struct{}|t] t
+        _[_ ~struct{}|t] t
+        _[_ struct{}|~t] t
+        _[_ ~struct{}|~t] t
+
+        _[_ t|struct{}] t
+        _[_ ~t|struct{}] t
+        _[_ t|~struct{}] t
+        _[_ ~t|~struct{}] t
+
+        // test cases for issue #49175
+        _[_ []t]t
+        _[_ [1]t]t
+        _[_ ~[]t]t
+        _[_ ~[1]t]t
+        t [ /* ERROR type parameters must be named */ t[0]]t
+)
+
+// test cases for issue #49174
+func _[_ t]() {}
+func _[_ []t]() {}
+func _[_ [1]t]() {}
+func _[_ []t | t]() {}
+func _[_ [1]t | t]() {}
+func _[_ t | []t]() {}
+func _[_ []t | []t]() {}
+func _[_ [1]t | [1]t]() {}
+func _[_ t[t] | t[t]]() {}
+
+// Single-expression type parameter lists and those that don't start
+// with a (type parameter) name are considered array sizes.
+// The term must be a valid expression (it could be a type - and then
+// a type-checker will complain - but we don't allow ~ in the expr).
+type (
+        _[t] t
+        _[/* ERROR unexpected ~ */ ~t] t
+        _[t|t] t
+        _[/* ERROR unexpected ~ */ ~t|t] t
+        _[t| /* ERROR unexpected ~ */ ~t] t
+        _[/* ERROR unexpected ~ */ ~t|~t] t
+)
+
+type (
+        _[_ t, t /* ERROR missing type constraint */ ] t
+        _[_ ~t, t /* ERROR missing type constraint */ ] t
+        _[_ t, /* ERROR type parameters must be named */ ~t] t
+        _[_ ~t, /* ERROR type parameters must be named */ ~t] t
+
+        _[_ t|t, /* ERROR type parameters must be named */ t|t] t
+        _[_ ~t|t, /* ERROR type parameters must be named */ t|t] t
+        _[_ t|t, /* ERROR type parameters must be named */ ~t|t] t
+        _[_ ~t|t, /* ERROR type parameters must be named */ ~t|t] t
+)