cmd/compile: reject slice/map/func comparisons against converted nil

Fixes #13480.

Change-Id: Icbf4f83e965e84f7020f56c3f346193f8b91e7bf
Reviewed-on: https://go-review.googlesource.com/17461
Reviewed-by: Russ Cox <rsc@golang.org>

diff --git a/src/cmd/compile/internal/gc/subr.go b/src/cmd/compile/internal/gc/subr.go
index 4d355517a30a84ed947777b20cc2f59416cc3ddf..163ecbc34c10f016c212ec36237c0ffe6b5ade53 100644 (file)
--- a/src/cmd/compile/internal/gc/subr.go
+++ b/src/cmd/compile/internal/gc/subr.go
@@ -760,17 +760,11 @@ func treecopy(n *Node, lineno int32) *Node {
        return m
 }
 
+// isnil reports whether n represents the universal untyped zero value "nil".
 func isnil(n *Node) bool {
-       if n == nil {
-               return false
-       }
-       if n.Op != OLITERAL {
-               return false
-       }
-       if n.Val().Ctype() != CTNIL {
-               return false
-       }
-       return true
+       // Check n.Orig because constant propagation may produce typed nil constants,
+       // which don't exist in the Go spec.
+       return Isconst(n.Orig, CTNIL)
 }
 
 func isptrto(t *Type, et EType) bool {

diff --git a/src/cmd/compile/internal/gc/swt.go b/src/cmd/compile/internal/gc/swt.go
index 3600e18268c8a4bc8bab7180cfbc997ee784172a..29e634cebde7366b54bc8fe2942d3409522f6d3e 100644 (file)
--- a/src/cmd/compile/internal/gc/swt.go
+++ b/src/cmd/compile/internal/gc/swt.go
@@ -137,7 +137,7 @@ func typecheckswitch(n *Node) {
                                                } else {
                                                        Yyerror("invalid case %v in switch (mismatched types %v and bool)", ll.N, ll.N.Type)
                                                }
-                                       case nilonly != "" && !Isconst(ll.N, CTNIL):
+                                       case nilonly != "" && !isnil(ll.N):
                                                Yyerror("invalid case %v in switch (can only compare %s %v to nil)", ll.N, nilonly, n.Left)
                                        }
 

diff --git a/test/fixedbugs/issue13480.go b/test/fixedbugs/issue13480.go
new file mode 100644 (file)
index 0000000..cd2f05d
--- /dev/null
+++ b/test/fixedbugs/issue13480.go
@@ -0,0 +1,38 @@
+// errorcheck
+
+// Copyright 2015 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.
+
+// Verify that comparisons of slice/map/func values against converted nil
+// values are properly rejected.
+
+package p
+
+func bug() {
+       type S []byte
+       type M map[int]int
+       type F func()
+
+       var s S
+       var m M
+       var f F
+
+       _ = s == S(nil) // ERROR "compare.*to nil"
+       _ = S(nil) == s // ERROR "compare.*to nil"
+       switch s {
+       case S(nil): // ERROR "compare.*to nil"
+       }
+
+       _ = m == M(nil) // ERROR "compare.*to nil"
+       _ = M(nil) == m // ERROR "compare.*to nil"
+       switch m {
+       case M(nil): // ERROR "compare.*to nil"
+       }
+
+       _ = f == F(nil) // ERROR "compare.*to nil"
+       _ = F(nil) == f // ERROR "compare.*to nil"
+       switch f {
+       case F(nil): // ERROR "compare.*to nil"
+       }
+}