test: add tests for escape analysis of slices

False positives (var incorrectly escapes) are marked with BAD.

Change-Id: I9e9a3f71b060520103bcf289829a2efdf6f2b517
Reviewed-on: https://go-review.googlesource.com/5298Reviewed-by: Keith Randall <khr@golang.org>

test/escape_slice.go

+// errorcheck -0 -m -l
+
+// 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.
+
+// Test escape analysis for slices.
+
+package escape
+
+var sink interface{}
+
+func slice0() {
+	var s []*int
+	// BAD: i should not escape
+	i := 0            // ERROR "moved to heap: i"
+	s = append(s, &i) // ERROR "&i escapes to heap"
+	_ = s
+}
+
+func slice1() *int {
+	var s []*int
+	i := 0            // ERROR "moved to heap: i"
+	s = append(s, &i) // ERROR "&i escapes to heap"
+	return s[0]
+}
+
+func slice2() []*int {
+	var s []*int
+	i := 0            // ERROR "moved to heap: i"
+	s = append(s, &i) // ERROR "&i escapes to heap"
+	return s
+}
+
+func slice3() *int {
+	var s []*int
+	i := 0            // ERROR "moved to heap: i"
+	s = append(s, &i) // ERROR "&i escapes to heap"
+	for _, p := range s {
+		return p
+	}
+	return nil
+}
+
+func slice4(s []*int) { // ERROR "s does not escape"
+	i := 0    // ERROR "moved to heap: i"
+	s[0] = &i // ERROR "&i escapes to heap"
+}
+
+func slice5(s []*int) { // ERROR "s does not escape"
+	if s != nil {
+		s = make([]*int, 10) // ERROR "make\(\[\]\*int, 10\) does not escape"
+	}
+	i := 0    // ERROR "moved to heap: i"
+	s[0] = &i // ERROR "&i escapes to heap"
+}
+
+func slice6() {
+	s := make([]*int, 10) // ERROR "make\(\[\]\*int, 10\) does not escape"
+	// BAD: i should not escape
+	i := 0    // ERROR "moved to heap: i"
+	s[0] = &i // ERROR "&i escapes to heap"
+	_ = s
+}
+
+func slice7() *int {
+	s := make([]*int, 10) // ERROR "make\(\[\]\*int, 10\) does not escape"
+	i := 0                // ERROR "moved to heap: i"
+	s[0] = &i             // ERROR "&i escapes to heap"
+	return s[0]
+}
+
+func slice8() {
+	// BAD: i should not escape here
+	i := 0          // ERROR "moved to heap: i"
+	s := []*int{&i} // ERROR "&i escapes to heap" "literal does not escape"
+	_ = s
+}
+
+func slice9() *int {
+	i := 0          // ERROR "moved to heap: i"
+	s := []*int{&i} // ERROR "&i escapes to heap" "literal does not escape"
+	return s[0]
+}
+
+func slice10() []*int {
+	i := 0          // ERROR "moved to heap: i"
+	s := []*int{&i} // ERROR "&i escapes to heap" "literal escapes to heap"
+	return s
+}