test: add compiler regress tests for #46461

gri@ reports that types2 now correctly handles when type parameters
recursively refer back to the parameterized type, so we might as well
add tests to exercise that. Unified IR also correctly handles
importing and exporting these types, but -G=3 currently does not.

Updates #46461.

Change-Id: I272102aa08c40c980b9aeeca9f834291dfbbcc3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/348738
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

6 files changed, 42 insertions, 0 deletions

diff --git a/src/go/internal/gcimporter/gcimporter_test.go b/src/go/internal/gcimporter/gcimporter_test.go
index 9f4345d8f9..478534daf2 100644
--- a/src/go/internal/gcimporter/gcimporter_test.go
+++ b/src/go/internal/gcimporter/gcimporter_test.go
@@ -167,6 +167,8 @@ func TestImportTypeparamTests(t *testing.T) {
 	skip := map[string]string{
 		"equal.go":  "inconsistent embedded sorting", // TODO(rfindley): investigate this.
 		"nested.go": "fails to compile",              // TODO(rfindley): investigate this.
+
+		"issue46461.go": "known issue with type parameter constraints referring back to parameterized type",
 	}
 
 	for _, entry := range list {
diff --git a/test/run.go b/test/run.go
index 790b54bfd2..d2b7b88768 100644
--- a/test/run.go
+++ b/test/run.go
@@ -2188,6 +2188,8 @@ var g3Failures = setOf(
 
 	"typeparam/nested.go", // -G=3 doesn't support function-local types with generics
 
+	"typeparam/issue46461b.go", // -G=3 fails when type parameters refer back to the parameterized type itself
+
 	"typeparam/mdempsky/4.go", // -G=3 can't export functions with labeled breaks in loops
 )
 
diff --git a/test/typeparam/issue46461.go b/test/typeparam/issue46461.go
new file mode 100644
index 0000000000..2c54a6ba28
--- /dev/null
+++ b/test/typeparam/issue46461.go
@@ -0,0 +1,13 @@
+// compile -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 p
+
+type T[U interface{ M() T[U] }] int
+
+type X int
+
+func (X) M() T[X] { return 0 }
diff --git a/test/typeparam/issue46461b.dir/a.go b/test/typeparam/issue46461b.dir/a.go
new file mode 100644
index 0000000000..0d53b3e204
--- /dev/null
+++ b/test/typeparam/issue46461b.dir/a.go
@@ -0,0 +1,7 @@
+// 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 a
+
+type T[U interface{ M() T[U] }] int
diff --git a/test/typeparam/issue46461b.dir/b.go b/test/typeparam/issue46461b.dir/b.go
new file mode 100644
index 0000000000..3393a375c2
--- /dev/null
+++ b/test/typeparam/issue46461b.dir/b.go
@@ -0,0 +1,11 @@
+// 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 b
+
+import "./a"
+
+type X int
+
+func (X) M() a.T[X] { return 0 }
diff --git a/test/typeparam/issue46461b.go b/test/typeparam/issue46461b.go
new file mode 100644
index 0000000000..87b4ff46c1
--- /dev/null
+++ b/test/typeparam/issue46461b.go
@@ -0,0 +1,7 @@
+// compiledir -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 ignored