cmd/compile: fix identical to recognize any and interface{}

Currently, identical handles any and interface{} by checking against
Types[TINTER]. This is not always true, since when two generated
interface{} types may not use the same *Type instance.

Instead, we must check whether Type is empty interface or not.

Fixes #49875

Change-Id: I28fe4fc0100041a01bb03da795cfe8232b515fc4
Reviewed-on: https://go-review.googlesource.com/c/go/+/367754
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/test/typeparam/issue49875.go b/test/typeparam/issue49875.go
new file mode 100644
index 0000000000..aece7deab1
--- /dev/null
+++ b/test/typeparam/issue49875.go
@@ -0,0 +1,14 @@
+// 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
+
+func f(args ...interface{}) {}
+
+func g() {
+	var args []any
+	f(args...)
+}