[release-branch.go1.19] cmd/compile: fix wrong typeparams for selector expr with...

For selector expression "x.M" where "M" is a promoted method, irgen is using
the type of receiver "x" for determining the typeparams for instantiation.
However, because M is a promoted method, so its associated receiver is
not "x", but "x.T" where "T" is the embedded field of "x". That casues a
mismatch when converting non-shape types arguments.

Fixing it by using the actual receiver which has the method, instead of
using the base receiver.

Fixes #54243

Change-Id: I1836fc422d734df14e9e6664d4bd014503960bfc
Reviewed-on: https://go-review.googlesource.com/c/go/+/419294
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/423114
Reviewed-by: Carlos Amedee <carlos@golang.org>

diff --git a/src/cmd/compile/internal/noder/stencil.go b/src/cmd/compile/internal/noder/stencil.go
index d3f51e00cd355cb6f9316e4a956fe2eff0f65379..6fcb31b472ecb56583f26952c2e07d521f434271 100644 (file)
--- a/src/cmd/compile/internal/noder/stencil.go
+++ b/src/cmd/compile/internal/noder/stencil.go
@@ -334,10 +334,6 @@ func (g *genInst) buildClosure(outer *ir.Func, x ir.Node) ir.Node {
        } else { // ir.OMETHEXPR or ir.METHVALUE
                // Method expression T.M where T is a generic type.
                se := x.(*ir.SelectorExpr)
-               targs := deref(se.X.Type()).RParams()
-               if len(targs) == 0 {
-                       panic("bad")
-               }
                if x.Op() == ir.OMETHVALUE {
                        rcvrValue = se.X
                }
@@ -348,7 +344,8 @@ func (g *genInst) buildClosure(outer *ir.Func, x ir.Node) ir.Node {
                // of se.Selection, since that will be the type that actually has
                // the method.
                recv := deref(se.Selection.Type.Recv().Type)
-               if len(recv.RParams()) == 0 {
+               targs := recv.RParams()
+               if len(targs) == 0 {
                        // The embedded type that actually has the method is not
                        // actually generic, so no need to build a closure.
                        return x

diff --git a/test/fixedbugs/issue53982.go b/test/fixedbugs/issue53982.go
new file mode 100644 (file)
index 0000000..512b1af
--- /dev/null
+++ b/test/fixedbugs/issue53982.go
@@ -0,0 +1,25 @@
+// build
+
+// 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 S[K, V any] struct {
+       E[V]
+}
+
+type E[K any] struct{}
+
+func (e E[K]) M() E[K] {
+       return e
+}
+
+func G[K, V any](V) {
+       _ = (*S[K, V]).M
+}
+
+func main() {
+       G[*int](new(int))
+}