cmd/gc: emit error for out-of-bounds slice of constant string

Fixes issue 7200.

LGTM=gri, iant
R=golang-codereviews, gri, iant
CC=golang-codereviews, r
https://codereview.appspot.com/150020044

1 files changed, 26 insertions, 3 deletions

diff --git a/test/fixedbugs/issue4232.go b/test/fixedbugs/issue4232.go
index e5daa6562..755b1b1de 100644
--- a/test/fixedbugs/issue4232.go
+++ b/test/fixedbugs/issue4232.go
@@ -4,6 +4,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// issue 4232
+// issue 7200
+
 package p
 
 func f() {
@@ -12,22 +15,42 @@ func f() {
 	_ = a[-1:] // ERROR "invalid slice index -1|index out of bounds"
 	_ = a[:-1] // ERROR "invalid slice index -1|index out of bounds"
 	_ = a[10]  // ERROR "invalid array index 10|index out of bounds"
+	_ = a[9:10]
+	_ = a[10:10]
+	_ = a[9:12]            // ERROR "invalid slice index 12|index out of bounds"
+	_ = a[11:12]           // ERROR "invalid slice index 11|index out of bounds"
+	_ = a[1<<100 : 1<<110] // ERROR "overflows int" "invalid slice index 1 << 100|index out of bounds"
 
 	var s []int
 	_ = s[-1]  // ERROR "invalid slice index -1|index out of bounds"
 	_ = s[-1:] // ERROR "invalid slice index -1|index out of bounds"
 	_ = s[:-1] // ERROR "invalid slice index -1|index out of bounds"
 	_ = s[10]
+	_ = s[9:10]
+	_ = s[10:10]
+	_ = s[9:12]
+	_ = s[11:12]
+	_ = s[1<<100 : 1<<110] // ERROR "overflows int" "invalid slice index 1 << 100|index out of bounds"
 
-	const c = "foo"
+	const c = "foofoofoof"
 	_ = c[-1]  // ERROR "invalid string index -1|index out of bounds"
 	_ = c[-1:] // ERROR "invalid slice index -1|index out of bounds"
 	_ = c[:-1] // ERROR "invalid slice index -1|index out of bounds"
-	_ = c[3]   // ERROR "invalid string index 3|index out of bounds"
+	_ = c[10]  // ERROR "invalid string index 10|index out of bounds"
+	_ = c[9:10]
+	_ = c[10:10]
+	_ = c[9:12]            // ERROR "invalid slice index 12|index out of bounds"
+	_ = c[11:12]           // ERROR "invalid slice index 11|index out of bounds"
+	_ = c[1<<100 : 1<<110] // ERROR "overflows int" "invalid slice index 1 << 100|index out of bounds"
 
 	var t string
 	_ = t[-1]  // ERROR "invalid string index -1|index out of bounds"
 	_ = t[-1:] // ERROR "invalid slice index -1|index out of bounds"
 	_ = t[:-1] // ERROR "invalid slice index -1|index out of bounds"
-	_ = t[3]
+	_ = t[10]
+	_ = t[9:10]
+	_ = t[10:10]
+	_ = t[9:12]
+	_ = t[11:12]
+	_ = t[1<<100 : 1<<110] // ERROR "overflows int" "invalid slice index 1 << 100|index out of bounds"
 }