From 7fa195c1b9650db3e91b90af6b16405e7e0ba9ce Mon Sep 17 00:00:00 2001
From: Matthew Dempsky <mdempsky@google.com>
Date: Wed, 27 Feb 2019 17:12:23 -0800
Subject: [PATCH] cmd/compile: fix false positives in isGoConst

isGoConst could spuriously return true for variables that shadow a
constant declaration with the same name.

Because even named constants are always represented by OLITERAL nodes,
the easy fix is to just ignore ONAME nodes in isGoConst. We can
similarly ignore ONONAME nodes.

Confirmed that k8s.io/kubernetes/test/e2e/storage builds again with
this fix.

Fixes #30430.

Change-Id: I899400d749982d341dc248a7cd5a18277c2795ec
Reviewed-on: https://go-review.googlesource.com/c/164319
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
---
 src/cmd/compile/internal/gc/const.go | 13 -------------
 test/fixedbugs/issue30430.go         | 17 +++++++++++++++++
 2 files changed, 17 insertions(+), 13 deletions(-)
 create mode 100644 test/fixedbugs/issue30430.go

diff --git a/src/cmd/compile/internal/gc/const.go b/src/cmd/compile/internal/gc/const.go
index de7df645e6..0e6d838eaa 100644
--- a/src/cmd/compile/internal/gc/const.go
+++ b/src/cmd/compile/internal/gc/const.go
@@ -1280,8 +1280,6 @@ func indexconst(n *Node) int64 {
 //
 // Expressions derived from nil, like string([]byte(nil)), while they
 // may be known at compile time, are not Go language constants.
-// Only called for expressions known to evaluate to compile-time
-// constants.
 func (n *Node) isGoConst() bool {
 	if n.Orig != nil {
 		n = n.Orig
@@ -1359,17 +1357,6 @@ func (n *Node) isGoConst() bool {
 			return true
 		}
 
-	case ONAME:
-		l := asNode(n.Sym.Def)
-		if l != nil && l.Op == OLITERAL && n.Val().Ctype() != CTNIL {
-			return true
-		}
-
-	case ONONAME:
-		if asNode(n.Sym.Def) != nil && asNode(n.Sym.Def).Op == OIOTA {
-			return true
-		}
-
 	case OALIGNOF, OOFFSETOF, OSIZEOF:
 		return true
 	}
diff --git a/test/fixedbugs/issue30430.go b/test/fixedbugs/issue30430.go
new file mode 100644
index 0000000000..6c27b82881
--- /dev/null
+++ b/test/fixedbugs/issue30430.go
@@ -0,0 +1,17 @@
+// compile
+
+// Copyright 2019 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 30430: isGoConst returned true for non-const variables,
+// resulting in ICE.
+
+package p
+
+func f() {
+	var s string
+	_ = map[string]string{s: ""}
+}
+
+const s = ""