1 files changed, 62 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/types2/instantiate_test.go b/src/cmd/compile/internal/types2/instantiate_test.go
new file mode 100644
index 00000000000..69a26491cb5
--- /dev/null
+++ b/src/cmd/compile/internal/types2/instantiate_test.go
@@ -0,0 +1,62 @@
+// 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 types2_test
+
+import (
+	. "cmd/compile/internal/types2"
+	"testing"
+)
+
+func TestInstantiateEquality(t *testing.T) {
+	const src = genericPkg + "p; type T[P any] int"
+	pkg, err := pkgFor(".", src, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	T := pkg.Scope().Lookup("T").Type().(*Named)
+	// Instantiating the same type twice should result in pointer-equivalent
+	// instances.
+	env := NewEnvironment()
+	res1, err := Instantiate(env, T, []Type{Typ[Int]}, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	res2, err := Instantiate(env, T, []Type{Typ[Int]}, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res1 != res2 {
+		t.Errorf("first instance (%s) not pointer-equivalent to second instance (%s)", res1, res2)
+	}
+}
+func TestInstantiateNonEquality(t *testing.T) {
+	const src = genericPkg + "p; type T[P any] int"
+	pkg1, err := pkgFor(".", src, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	pkg2, err := pkgFor(".", src, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// We consider T1 and T2 to be distinct types, so their instances should not
+	// be deduplicated by the environment.
+	T1 := pkg1.Scope().Lookup("T").Type().(*Named)
+	T2 := pkg2.Scope().Lookup("T").Type().(*Named)
+	env := NewEnvironment()
+	res1, err := Instantiate(env, T1, []Type{Typ[Int]}, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	res2, err := Instantiate(env, T2, []Type{Typ[Int]}, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res1 == res2 {
+		t.Errorf("instance from pkg1 (%s) is pointer-equivalent to instance from pkg2 (%s)", res1, res2)
+	}
+	if Identical(res1, res2) {
+		t.Errorf("instance from pkg1 (%s) is identical to instance from pkg2 (%s)", res1, res2)
+	}
+}