cmd/compile: fix dictionaries for nested closures

Capturing dictionary closure variables is ok.

Fixes #47684

Change-Id: I049c87117915e0c5a172b9665bfac2f91064b2d4
Reviewed-on: https://go-review.googlesource.com/c/go/+/342050
Trust: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>

diff --git a/src/cmd/compile/internal/ir/name.go b/src/cmd/compile/internal/ir/name.go
index a2eec05013e1092076ec62524c1f3235bc5d1fd1..48fe57212470a42ce24cea0a06729785138a704c 100644 (file)
--- a/src/cmd/compile/internal/ir/name.go
+++ b/src/cmd/compile/internal/ir/name.go
@@ -404,7 +404,9 @@ func CaptureName(pos src.XPos, fn *Func, n *Name) *Name {
        if n.Op() != ONAME || n.Curfn == nil {
                return n // okay to use directly
        }
-       if n.IsClosureVar() {
+       if n.IsClosureVar() && n.Sym().Name != ".dict" {
+               // Note: capturing dictionary closure variables is ok. This makes
+               // sure the generated code is correctly optimized.
                base.FatalfAt(pos, "misuse of CaptureName on closure variable: %v", n)
        }
 

diff --git a/test/typeparam/issue47684.go b/test/typeparam/issue47684.go
new file mode 100644 (file)
index 0000000..2798b78
--- /dev/null
+++ b/test/typeparam/issue47684.go
@@ -0,0 +1,19 @@
+// run -gcflags=-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 main
+
+func f[G any]() int {
+       return func() int {
+               return func() int {
+                       return 0
+               }()
+       }()
+}
+
+func main() {
+       f[int]()
+}

diff --git a/test/typeparam/issue47684b.go b/test/typeparam/issue47684b.go
new file mode 100644 (file)
index 0000000..c43ef8d
--- /dev/null
+++ b/test/typeparam/issue47684b.go
@@ -0,0 +1,23 @@
+// run -gcflags=-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 main
+
+func f[G any]() interface{} {
+       return func() interface{} {
+               return func() interface{} {
+                       var x G
+                       return x
+               }()
+       }()
+}
+
+func main() {
+       x := f[int]()
+       if v, ok := x.(int); !ok || v != 0 {
+               panic("bad")
+       }
+}

diff --git a/test/typeparam/issue47684c.go b/test/typeparam/issue47684c.go
new file mode 100644 (file)
index 0000000..32f1b66
--- /dev/null
+++ b/test/typeparam/issue47684c.go
@@ -0,0 +1,19 @@
+// run -gcflags=-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 main
+
+func f[G any]() func()func()int {
+       return func() func()int {
+               return func() int {
+                       return 0
+               }
+       }
+}
+
+func main() {
+       f[int]()()()
+}