[release-branch.go1.18] cmd/compile: only check implicit dots for method call enabled by a type bound

Fixes #53723

Change-Id: Ibad64f5c4af2112deeb0a9ecc9c589b17594bd05
Reviewed-on: https://go-review.googlesource.com/c/go/+/414836
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/416155
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>

src/cmd/compile/internal/noder/stencil.go

@@ -1599,12 +1599,14 @@ func (g *genInst) getDictionarySym(gf *ir.Name, targs []*types.Type, isMeth bool
 				se := call.X.(*ir.SelectorExpr)
 				if se.X.Type().IsShape() {
 					// This is a method call enabled by a type bound.
-
-					// We need this extra check for method expressions,
-					// which don't add in the implicit XDOTs.
-					tmpse := ir.NewSelectorExpr(src.NoXPos, ir.OXDOT, se.X, se.Sel)
-					tmpse = typecheck.AddImplicitDots(tmpse)
-					tparam := tmpse.X.Type()
+					tparam := se.X.Type()
+					if call.X.Op() == ir.ODOTMETH {
+						// We need this extra check for method expressions,
+						// which don't add in the implicit XDOTs.
+						tmpse := ir.NewSelectorExpr(src.NoXPos, ir.OXDOT, se.X, se.Sel)
+						tmpse = typecheck.AddImplicitDots(tmpse)
+						tparam = tmpse.X.Type()
+					}
 					if !tparam.IsShape() {
 						// The method expression is not
 						// really on a typeparam.

test/typeparam/issue53419.go

@@ -0,0 +1,28 @@
+// run -gcflags=-G=3
+
+// Copyright 2022 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 main
+
+type T1 struct{}
+type T2 struct{}
+type Both struct {
+	T1
+	T2
+}
+
+func (T1) m()   { panic("FAIL") }
+func (T2) m()   { panic("FAIL") }
+func (Both) m() {}
+
+func f[T interface{ m() }](c T) {
+	c.m()
+}
+
+func main() {
+	var b Both
+	b.m()
+	f(b)
+}