1 files changed, 106 insertions, 0 deletions
diff --git a/test/interface/explicit.go b/test/interface/explicit.go
new file mode 100644
index 0000000..e18d684
--- /dev/null
+++ b/test/interface/explicit.go
@@ -0,0 +1,106 @@
+// errorcheck
+
+// Copyright 2009 The Go 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 compiler messages about erroneous static interface conversions.
+// Does not compile.
+
+package main
+
+type T struct {
+	a int
+}
+
+var t *T
+
+type X int
+
+func (x *X) M() {}
+
+type I interface {
+	M()
+}
+
+var i I
+
+type I2 interface {
+	M()
+	N()
+}
+
+var i2 I2
+
+type E interface{}
+
+var e E
+
+func main() {
+	e = t // ok
+	t = e // ERROR "need explicit|need type assertion"
+
+	// neither of these can work,
+	// because i has an extra method
+	// that t does not, so i cannot contain a t.
+	i = t // ERROR "incompatible|missing M method"
+	t = i // ERROR "incompatible|assignment$"
+
+	i = i2 // ok
+	i2 = i // ERROR "incompatible|missing N method"
+
+	i = I(i2)  // ok
+	i2 = I2(i) // ERROR "invalid|missing N method|cannot convert"
+
+	e = E(t) // ok
+	t = T(e) // ERROR "need explicit|need type assertion|incompatible|cannot convert"
+
+	// cannot type-assert non-interfaces
+	f := 2.0
+	_ = f.(int) // ERROR "non-interface type|only valid for interface types|not an interface"
+
+}
+
+type M interface {
+	M()
+}
+
+var m M
+
+var _ = m.(int) // ERROR "impossible type assertion"
+
+type Int int
+
+func (Int) M(float64) {}
+
+var _ = m.(Int) // ERROR "impossible type assertion"
+
+var _ = m.(X) // ERROR "pointer receiver"
+
+var ii int
+var jj Int
+
+var m1 M = ii // ERROR "incompatible|missing"
+var m2 M = jj // ERROR "incompatible|wrong type for M method"
+
+var m3 = M(ii) // ERROR "invalid|missing|cannot convert"
+var m4 = M(jj) // ERROR "invalid|wrong type for M method|cannot convert"
+
+type B1 interface {
+	_() // ERROR "methods must have a unique non-blank name"
+}
+
+type B2 interface {
+	M()
+	_() // ERROR "methods must have a unique non-blank name"
+}
+
+type T2 struct{}
+
+func (t *T2) M() {}
+func (t *T2) _() {}
+
+// Already reported about the invalid blank interface method above;
+// no need to report about not implementing it.
+var b1 B1 = &T2{}
+var b2 B2 = &T2{}