cmd/compile: prevent compiling closures more than once

Since CL 282892, functions are always compiled before closures. To do
that, when walking the closure, it is added to its outer function queue
for scheduling compilation later. Thus, a closure may be added to queue
more than once, causing the ICE dues to being compiled twice.

To fix this, catching the re-walking of the closure expression and do
not add it to the compilation queue.

Fixes #49029

Change-Id: I7d188e8f5b4d5c4248a0d8e6389da26f1084e464
Reviewed-on: https://go-review.googlesource.com/c/go/+/357960
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: Keith Randall <khr@golang.org>

src/cmd/compile/internal/walk/closure.go

@@ -107,7 +107,16 @@ func walkClosure(clo *ir.ClosureExpr, init *ir.Nodes) ir.Node {
 	// The closure is not trivial or directly called, so it's going to stay a closure.
 	ir.ClosureDebugRuntimeCheck(clo)
 	clofn.SetNeedctxt(true)
-	ir.CurFunc.Closures = append(ir.CurFunc.Closures, clofn)
+
+	// The closure expression may be walked more than once if it appeared in composite
+	// literal initialization (e.g, see issue #49029).
+	//
+	// Don't add the closure function to compilation queue more than once, since when
+	// compiling a function twice would lead to an ICE.
+	if !clofn.Walked() {
+		clofn.SetWalked(true)
+		ir.CurFunc.Closures = append(ir.CurFunc.Closures, clofn)
+	}
 
 	typ := typecheck.ClosureType(clo)
 

test/fixedbugs/issue49029.go

@@ -0,0 +1,25 @@
+// 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.
+
+package p
+
+type s struct {
+	f func()
+}
+
+func f() {
+	ch := make(chan struct{}, 1)
+	_ = [...]struct{ slice []s }{
+		{}, {}, {}, {},
+		{
+			slice: []s{
+				{
+					f: func() { ch <- struct{}{} },
+				},
+			},
+		},
+	}
+}