cmd/compile: fix panic with nested dead hidden closures

CL 342350 fixed deadcode panic with dead hidden closures. However, a
closure may contains nested dead hidden closures, so we need to mark
them dead as well.

Fixes #51839

Change-Id: Ib54581adfc1bdea60e74d733cd30fd8e783da983
Reviewed-on: https://go-review.googlesource.com/c/go/+/394079
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/cmd/compile/internal/deadcode/deadcode.go

@@ -163,4 +163,5 @@ func markHiddenClosureDead(n ir.Node) {
 	if clo.Func.IsHiddenClosure() {
 		clo.Func.SetIsDeadcodeClosure(true)
 	}
+	ir.VisitList(clo.Func.Body, markHiddenClosureDead)
 }

test/fixedbugs/issue51839.go

@@ -0,0 +1,22 @@
+// 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
+
+func main() {
+	testRecover()
+
+}
+
+func testRecover() {
+	if false {
+		func() {
+			defer func() {
+				_ = recover()
+			}()
+		}()
+	}
+}