[dev.typeparams] cmd/compile: fix missing condition in usemethod

CL 330670 simplified usemethod, but dropped the previous condition to
ensure the function have 1 or 2 result. This CL restore that condition,
and also add a test for it.

Change-Id: I434e3736785b43ceea0b386d8d9d01ad78a4ccd2
Reviewed-on: https://go-review.googlesource.com/c/go/+/336609
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: Matthew Dempsky <mdempsky@google.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/test/reflectmethod8.go b/test/reflectmethod8.go
new file mode 100644
index 0000000000..482163bae6
--- /dev/null
+++ b/test/reflectmethod8.go
@@ -0,0 +1,26 @@
+// 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.
+
+// Make sure that the compiler can analyze non-reflect
+// Type.{Method,MethodByName} calls.
+
+package p
+
+type I interface {
+	MethodByName(string)
+	Method(int)
+}
+
+type M struct{}
+
+func (M) MethodByName(string) {}
+func (M) Method(int)          {}
+
+func f() {
+	var m M
+	I.MethodByName(m, "")
+	I.Method(m, 42)
+}