1 files changed, 59 insertions, 0 deletions
diff --git a/src/internal/types/testdata/examples/typesets.go b/src/internal/types/testdata/examples/typesets.go
new file mode 100644
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+++ b/src/internal/types/testdata/examples/typesets.go
@@ -0,0 +1,59 @@
+// 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.
+
+// This file shows some examples of constraint literals with elided interfaces.
+// These examples are permitted if proposal issue #48424 is accepted.
+
+package p
+
+// Constraint type sets of the form T, ~T, or A|B may omit the interface.
+type (
+	_[T int]            struct{}
+	_[T ~int]           struct{}
+	_[T int | string]   struct{}
+	_[T ~int | ~string] struct{}
+)
+
+func min[T int | string](x, y T) T {
+	if x < y {
+		return x
+	}
+	return y
+}
+
+func lookup[M ~map[K]V, K comparable, V any](m M, k K) V {
+	return m[k]
+}
+
+func deref[P ~*E, E any](p P) E {
+	return *p
+}
+
+func _() int {
+	p := new(int)
+	return deref(p)
+}
+
+func addrOfCopy[V any, P *V](v V) P {
+	return &v
+}
+
+func _() *int {
+	return addrOfCopy(0)
+}
+
+// A type parameter may not be embedded in an interface;
+// so it can also not be used as a constraint.
+func _[A any, B A /* ERROR cannot use a type parameter as constraint */]()    {}
+func _[A any, B, C A /* ERROR cannot use a type parameter as constraint */]() {}
+
+// Error messages refer to the type constraint as it appears in the source.
+// (No implicit interface should be exposed.)
+func _[T string](x T) T {
+	return x /* ERROR constrained by string */ * x
+}
+
+func _[T int | string](x T) T {
+	return x /* ERROR constrained by int|string */ * x
+}