1 files changed, 88 insertions, 0 deletions
diff --git a/test/typeparam/stringer.go b/test/typeparam/stringer.go
new file mode 100644
index 0000000000..81290d599e
--- /dev/null
+++ b/test/typeparam/stringer.go
@@ -0,0 +1,88 @@
+// run -gcflags=-G=3
+
+// 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.
+
+// Test method calls on type parameters
+
+package main
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+)
+
+// Simple constraint
+type Stringer interface {
+	String() string
+}
+
+func stringify[T Stringer](s []T) (ret []string) {
+	for _, v := range s {
+		ret = append(ret, v.String())
+	}
+	return ret
+}
+
+type myint int
+
+func (i myint) String() string {
+	return strconv.Itoa(int(i))
+}
+
+// Constraint with an embedded interface, but still only requires String()
+type Stringer2 interface {
+	CanBeStringer2() int
+	SubStringer2
+}
+
+type SubStringer2 interface {
+	CanBeSubStringer2() int
+	String() string
+}
+
+func stringify2[T Stringer2](s []T) (ret []string) {
+	for _, v := range s {
+		ret = append(ret, v.String())
+	}
+	return ret
+}
+
+func (myint) CanBeStringer2() int {
+	return 0
+}
+
+func (myint) CanBeSubStringer2() int {
+	return 0
+}
+
+// Test use of method values that are not called
+func stringify3[T Stringer](s []T) (ret []string) {
+	for _, v := range s {
+		f := v.String
+		ret = append(ret, f())
+	}
+	return ret
+}
+
+func main() {
+	x := []myint{myint(1), myint(2), myint(3)}
+
+	got := stringify(x)
+	want := []string{"1", "2", "3"}
+	if !reflect.DeepEqual(got, want) {
+		panic(fmt.Sprintf("got %s, want %s", got, want))
+	}
+
+	got = stringify2(x)
+	if !reflect.DeepEqual(got, want) {
+		panic(fmt.Sprintf("got %s, want %s", got, want))
+	}
+
+	got = stringify3(x)
+	if !reflect.DeepEqual(got, want) {
+		panic(fmt.Sprintf("got %s, want %s", got, want))
+	}
+}