1 files changed, 53 insertions, 0 deletions
diff --git a/test/fixedbugs/issue18595.go b/test/fixedbugs/issue18595.go
new file mode 100644
index 0000000..d6f07b3
--- /dev/null
+++ b/test/fixedbugs/issue18595.go
@@ -0,0 +1,53 @@
+// run
+
+// 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.
+
+// This test makes sure that itabs are unique.
+// More explicitly, we require that only one itab structure exists for the pair of
+// a given compile-time interface type and underlying concrete type.
+// Ensuring this invariant enables fixes for 18492 (improve type switch code).
+
+package main
+
+type I interface {
+	M()
+}
+type J interface {
+	M()
+}
+
+type T struct{}
+
+func (*T) M() {}
+
+func main() {
+	test1()
+	test2()
+}
+
+func test1() {
+	t := new(T)
+	var i1, i2 I
+	var j interface {
+		M()
+	}
+	i1 = t
+	j = t
+	i2 = j
+	if i1 != i2 {
+		panic("interfaces not equal")
+	}
+}
+
+func test2() {
+	t := new(T)
+	i1 := (I)(t)
+	i2 := (I)((interface {
+		M()
+	})((J)(t)))
+	if i1 != i2 {
+		panic("interfaces not equal")
+	}
+}