cmd/gc: do not corrupt init() with initializers of _ in closures.

Fixes #5607.

R=golang-dev, daniel.morsing, r, dsymonds
CC=golang-dev
https://golang.org/cl/9952043

src/cmd/gc/sinit.c

@@ -50,8 +50,11 @@ init1(Node *n, NodeList **out)
 	case PFUNC:
 		break;
 	default:
-		if(isblank(n) && n->defn != N && n->defn->initorder == InitNotStarted) {
+		if(isblank(n) && n->curfn == N && n->defn != N && n->defn->initorder == InitNotStarted) {
+			// blank names initialization is part of init() but not
+			// when they are inside a function.
 			n->defn->initorder = InitDone;
+			if(debug['%']) dump("nonstatic", n->defn);
 			*out = list(*out, n->defn);
 		}
 		return;
@@ -149,6 +152,7 @@ if(debug['%']) dump("nonstatic", n->defn);
 			n->defn->initorder = InitDone;
 			for(l=n->defn->rlist; l; l=l->next)
 				init1(l->n, out);
+			if(debug['%']) dump("nonstatic", n->defn);
 			*out = list(*out, n->defn);
 			break;
 		}

test/fixedbugs/issue5607.go

@@ -0,0 +1,36 @@
+// run
+
+// Copyright 2013 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.
+
+// Issue 5607: generation of init() function incorrectly
+// uses initializers of blank variables inside closures.
+
+package main
+
+var Test = func() {
+	var mymap = map[string]string{"a": "b"}
+
+	var innerTest = func() {
+		// Used to crash trying to compile this line as
+		// part of init() (funcdepth mismatch).
+		var _, x = mymap["a"]
+		println(x)
+	}
+	innerTest()
+}
+
+var Test2 = func() {
+	// The following initializer should not be part of init()
+	// The compiler used to generate a call to Panic() in init().
+	var _, x = Panic()
+	_ = x
+}
+
+func Panic() (int, int) {
+	panic("omg")
+	return 1, 2
+}
+
+func main() {}