cmd/compile/internal/syntax: accept "~" and "|" interface elements

Type lists continue to be accepted as before.

While at it, print missing filenames in error tests
(which uses an ad-hoc position representation).

Change-Id: I933b3acbc9cf1985ad8f70f6b206e3a1dbd64d1e
Reviewed-on: https://go-review.googlesource.com/c/go/+/307371
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/syntax/testdata/interface.go2 b/src/cmd/compile/internal/syntax/testdata/interface.go2
new file mode 100644
index 0000000000..a817327a43
--- /dev/null
+++ b/src/cmd/compile/internal/syntax/testdata/interface.go2
@@ -0,0 +1,36 @@
+// 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 contains test cases for interfaces containing
+// constraint elements.
+//
+// For now, we accept both ordinary type lists and the
+// more complex constraint elements.
+
+package p
+
+type _ interface {
+	m()
+	type int
+	type int, string
+	E
+}
+
+type _ interface {
+	m()
+	~int
+	int | string
+	int | ~string
+	~int | ~string
+}
+
+
+type _ interface {
+	m()
+	~int
+	T[int, string] | string
+	int | ~T[string, struct{}]
+	~int | ~string
+	type bool, int, float64
+}