1 files changed, 47 insertions, 0 deletions
diff --git a/test/typeparam/issue47925d.go b/test/typeparam/issue47925d.go
new file mode 100644
index 0000000..c5647f9
--- /dev/null
+++ b/test/typeparam/issue47925d.go
@@ -0,0 +1,47 @@
+// run
+
+// 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 I[T any] interface {
+	foo()
+}
+
+type J[T any] interface {
+	foo()
+	bar()
+}
+
+//go:noinline
+func f[T J[T]](x T, g func(T) T) I[T] {
+	// contains a cast between two nonempty interfaces
+	// Also make sure we don't evaluate g(x) twice.
+	return I[T](J[T](g(x)))
+}
+
+type S struct {
+	x int
+}
+
+func (s *S) foo() {}
+func (s *S) bar() {}
+
+var cnt int
+
+func inc(s *S) *S {
+	cnt++
+	return s
+}
+
+func main() {
+	i := f(&S{x: 7}, inc)
+	if i.(*S).x != 7 {
+		panic("bad")
+	}
+	if cnt != 1 {
+		panic("multiple calls")
+	}
+}