test: add escape analysis tests form maps

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

Change-Id: I8383fa3f77e2156d781d994968636ba9a17bb975
Reviewed-on: https://go-review.googlesource.com/5297Reviewed-by: Keith Randall <khr@golang.org>

test/escape_map.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 maps.
+
+package escape
+
+var sink interface{}
+
+func map0() {
+	m := make(map[*int]*int) // ERROR "make\(map\[\*int\]\*int, 0\) does not escape"
+	// BAD: i should not escape
+	i := 0 // ERROR "moved to heap: i"
+	// BAD: j should not escape
+	j := 0     // ERROR "moved to heap: j"
+	m[&i] = &j // ERROR "&i escapes to heap" "&j escapes to heap"
+	_ = m
+}
+
+func map1() *int {
+	m := make(map[*int]*int) // ERROR "make\(map\[\*int\]\*int, 0\) does not escape"
+	// BAD: i should not escape
+	i := 0       // ERROR "moved to heap: i"
+	j := 0       // ERROR "moved to heap: j"
+	m[&i] = &j   // ERROR "&i escapes to heap" "&j escapes to heap"
+	return m[&i] // ERROR "&i does not escape"
+}
+
+func map2() map[*int]*int {
+	m := make(map[*int]*int) // ERROR "make\(map\[\*int\]\*int, 0\) escapes to heap"
+	i := 0                   // ERROR "moved to heap: i"
+	j := 0                   // ERROR "moved to heap: j"
+	m[&i] = &j               // ERROR "&i escapes to heap" "&j escapes to heap"
+	return m
+}
+
+func map3() []*int {
+	m := make(map[*int]*int) // ERROR "make\(map\[\*int\]\*int, 0\) does not escape"
+	i := 0                   // ERROR "moved to heap: i"
+	// BAD: j should not escape
+	j := 0     // ERROR "moved to heap: j"
+	m[&i] = &j // ERROR "&i escapes to heap" "&j escapes to heap"
+	var r []*int
+	for k := range m {
+		r = append(r, k)
+	}
+	return r
+}
+
+func map4() []*int {
+	m := make(map[*int]*int) // ERROR "make\(map\[\*int\]\*int, 0\) does not escape"
+	// BAD: i should not escape
+	i := 0     // ERROR "moved to heap: i"
+	j := 0     // ERROR "moved to heap: j"
+	m[&i] = &j // ERROR "&i escapes to heap" "&j escapes to heap"
+	var r []*int
+	for k, v := range m {
+		// We want to test exactly "for k, v := range m" rather than "for _, v := range m".
+		// The following if is merely to use (but not leak) k.
+		if k != nil {
+			r = append(r, v)
+		}
+	}
+	return r
+}
+
+func map5(m map[*int]*int) { // ERROR "m does not escape"
+	i := 0     // ERROR "moved to heap: i"
+	j := 0     // ERROR "moved to heap: j"
+	m[&i] = &j // ERROR "&i escapes to heap" "&j escapes to heap"
+}
+
+func map6(m map[*int]*int) { // ERROR "m does not escape"
+	if m != nil {
+		m = make(map[*int]*int) // ERROR "make\(map\[\*int\]\*int, 0\) does not escape"
+	}
+	i := 0     // ERROR "moved to heap: i"
+	j := 0     // ERROR "moved to heap: j"
+	m[&i] = &j // ERROR "&i escapes to heap" "&j escapes to heap"
+}
+
+func map7() {
+	// BAD: i should not escape
+	i := 0 // ERROR "moved to heap: i"
+	// BAD: j should not escape
+	j := 0                     // ERROR "moved to heap: j"
+	m := map[*int]*int{&i: &j} // ERROR "&i escapes to heap" "&j escapes to heap" "literal does not escape"
+	_ = m
+}
+
+func map8() {
+	i := 0                     // ERROR "moved to heap: i"
+	j := 0                     // ERROR "moved to heap: j"
+	m := map[*int]*int{&i: &j} // ERROR "&i escapes to heap" "&j escapes to heap" "literal escapes to heap"
+	sink = m
+}
+
+func map9() *int {
+	// BAD: i should not escape
+	i := 0                     // ERROR "moved to heap: i"
+	j := 0                     // ERROR "moved to heap: j"
+	m := map[*int]*int{&i: &j} // ERROR "&i escapes to heap" "&j escapes to heap" "literal does not escape"
+	return m[nil]
+}