1 files changed, 86 insertions, 0 deletions
diff --git a/test/typeparam/dottype.go b/test/typeparam/dottype.go
new file mode 100644
index 0000000000..c9c900c096
--- /dev/null
+++ b/test/typeparam/dottype.go
@@ -0,0 +1,86 @@
+// 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.
+
+package main
+
+func f[T any](x interface{}) T {
+	return x.(T)
+}
+func f2[T any](x interface{}) (T, bool) {
+	t, ok := x.(T)
+	return t, ok
+}
+
+type I interface {
+	foo()
+}
+
+type myint int
+
+func (myint) foo() {
+}
+
+type myfloat float64
+
+func (myfloat) foo() {
+}
+
+func g[T I](x I) T {
+	return x.(T)
+}
+func g2[T I](x I) (T, bool) {
+	t, ok := x.(T)
+	return t, ok
+}
+
+func h[T any](x interface{}) struct{ a, b T } {
+	return x.(struct{ a, b T })
+}
+
+func k[T any](x interface{}) interface{ bar() T } {
+	return x.(interface{ bar() T })
+}
+
+type mybar int
+
+func (x mybar) bar() int {
+	return int(x)
+}
+
+func main() {
+	var i interface{} = int(3)
+	var j I = myint(3)
+	var x interface{} = float64(3)
+	var y I = myfloat(3)
+
+	println(f[int](i))
+	shouldpanic(func() { f[int](x) })
+	println(f2[int](i))
+	println(f2[int](x))
+
+	println(g[myint](j))
+	shouldpanic(func() { g[myint](y) })
+	println(g2[myint](j))
+	println(g2[myint](y))
+
+	println(h[int](struct{ a, b int }{3, 5}).a)
+
+	println(k[int](mybar(3)).bar())
+
+	type large struct {a,b,c,d,e,f int}
+	println(f[large](large{}).a)
+	l2, ok := f2[large](large{})
+	println(l2.a, ok)
+}
+func shouldpanic(x func()) {
+	defer func() {
+		e := recover()
+		if e == nil {
+			panic("didn't panic")
+		}
+	}()
+	x()
+}