[dev.typeparams] cmd/compile: allow nil Syms in Sym.Less

Allows sorting interfaces that contain embedded anonymous types.

Fixes #46556.

Change-Id: If19afa1d62432323b2e98957087867afbf3f9097
Reviewed-on: https://go-review.googlesource.com/c/go/+/324812
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/test/fixedbugs/issue46556.go b/test/fixedbugs/issue46556.go
new file mode 100644
index 0000000000..b159f61b0c
--- /dev/null
+++ b/test/fixedbugs/issue46556.go
@@ -0,0 +1,16 @@
+// compile
+
+// 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 A = interface{}
+type B interface{}
+
+// Test that embedding both anonymous and defined types is supported.
+type C interface {
+	A
+	B
+}