cmd/compile: don't use dictionary convert to shaped empty interface

Fixes: #53254
Change-Id: I3153d6ebb9f25957b09363f45c5cd4651ee84c2d
Reviewed-on: https://go-review.googlesource.com/c/go/+/410655
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Wayne Zuo <wdvxdr@golangcn.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>

diff --git a/src/cmd/compile/internal/noder/stencil.go b/src/cmd/compile/internal/noder/stencil.go
index d463c850f3620935fd133c36644d378659349f4d..89869c77d6ce47b5643944f098c1cb06eec7044c 100644 (file)
--- a/src/cmd/compile/internal/noder/stencil.go
+++ b/src/cmd/compile/internal/noder/stencil.go
@@ -1349,7 +1349,7 @@ func (g *genInst) dictPass(info *instInfo) {
                        mce := m.(*ir.ConvExpr)
                        // Note: x's argument is still typed as a type parameter.
                        // m's argument now has an instantiated type.
-                       if mce.X.Type().HasShape() || m.Type().HasShape() {
+                       if mce.X.Type().HasShape() || (m.Type().HasShape() && !m.Type().IsEmptyInterface()) {
                                m = convertUsingDictionary(info, info.dictParam, m.Pos(), mce.X, m, m.Type())
                        }
                case ir.ODOTTYPE, ir.ODOTTYPE2:
@@ -1446,7 +1446,7 @@ func findDictType(info *instInfo, t *types.Type) int {
 // instantiated node of the CONVIFACE node or XDOT node (for a bound method call) that is causing the
 // conversion.
 func convertUsingDictionary(info *instInfo, dictParam *ir.Name, pos src.XPos, v ir.Node, in ir.Node, dst *types.Type) ir.Node {
-       assert(v.Type().HasShape() || in.Type().HasShape())
+       assert(v.Type().HasShape() || (in.Type().HasShape() && !in.Type().IsEmptyInterface()))
        assert(dst.IsInterface())
 
        if v.Type().IsInterface() {

diff --git a/test/typeparam/issue53254.go b/test/typeparam/issue53254.go
new file mode 100644 (file)
index 0000000..afc0f18
--- /dev/null
+++ b/test/typeparam/issue53254.go
@@ -0,0 +1,19 @@
+// compile
+
+// 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 Interface[T any] interface {
+}
+
+func F[T any]() Interface[T] {
+       var i int
+       return i
+}
+
+func main() {
+       F[int]()
+}