cmd/gc: fix defer copy(x, <-c)

In the first very rough draft of the reordering code
that was introduced in the Go 1.3 cycle, the pre-allocated
temporary for a ... argument was held in n->right.
It moved to n->alloc but the code avoiding n->right
was left behind in order.c. In copy(x, <-c), the receive
is in n->right and must be processed. Delete the special
case code, removing the bug.

Fixes issue 8039.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://codereview.appspot.com/100820044

1 files changed, 23 insertions, 0 deletions

diff --git a/test/fixedbugs/issue8039.go b/test/fixedbugs/issue8039.go
new file mode 100644
index 000000000..b13e474d9
--- /dev/null
+++ b/test/fixedbugs/issue8039.go
@@ -0,0 +1,23 @@
+// run
+
+// 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.
+
+// issue 8039. defer copy(x, <-c) did not rewrite <-c properly.
+
+package main
+
+func f(s []int) {
+	c := make(chan []int, 1)
+	c <- []int{1}
+	defer copy(s, <-c)
+}
+
+func main() {
+	x := make([]int, 1)
+	f(x)
+	if x[0] != 1 {
+		println("BUG", x[0])
+	}
+}