cmd/gc: don't walk static nodes generated by anylit.

During anylit run, nodes such as SLICEARR(statictmp, [:])
may be generated and are expected to be found unchanged by
gen_as_init.

In some walks (in particular walkselect), the statement
may be walked again and lowered to its usual form, leading to a
crash.

Fixes issue 8017.
Fixes issue 8024.
Fixes issue 8058.

LGTM=rsc
R=golang-codereviews, dvyukov, gobot, rsc
CC=golang-codereviews
https://codereview.appspot.com/112080043

1 files changed, 26 insertions, 0 deletions

diff --git a/test/fixedbugs/issue8017.go b/test/fixedbugs/issue8017.go
new file mode 100644
index 000000000..22056e08c
--- /dev/null
+++ b/test/fixedbugs/issue8017.go
@@ -0,0 +1,26 @@
+// compile
+
+// Copyright 2014 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.
+
+// Issues 8017 and 8058: walk modifies nodes generated
+// by slicelit and causes an internal error afterwards
+// when gen_as_init parses it back.
+
+package main
+
+func F() {
+	var ch chan int
+	select {
+	case <-ch:
+	case <-make(chan int, len([2][]int{([][]int{})[len(ch)], []int{}})):
+	}
+}
+
+func G() {
+	select {
+	case <-([1][]chan int{[]chan int{}})[0][0]:
+	default:
+	}
+}