1 files changed, 89 insertions, 0 deletions
diff --git a/test/mapclear.go b/test/mapclear.go
new file mode 100644
index 0000000..a29f30d
--- /dev/null
+++ b/test/mapclear.go
@@ -0,0 +1,89 @@
+// run
+
+// Copyright 2018 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.
+
+// Ensure that range loops over maps with delete statements
+// have the requisite side-effects.
+
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func checkcleared() {
+	m := make(map[byte]int)
+	m[1] = 1
+	m[2] = 2
+	for k := range m {
+		delete(m, k)
+	}
+	l := len(m)
+	if want := 0; l != want {
+		fmt.Printf("len after map clear = %d want %d\n", l, want)
+		os.Exit(1)
+	}
+
+	m[0] = 0 // To have non empty map and avoid internal map code fast paths.
+	n := 0
+	for range m {
+		n++
+	}
+	if want := 1; n != want {
+		fmt.Printf("number of keys found = %d want %d\n", n, want)
+		os.Exit(1)
+	}
+}
+
+func checkloopvars() {
+	k := 0
+	m := make(map[int]int)
+	m[42] = 0
+	for k = range m {
+		delete(m, k)
+	}
+	if want := 42; k != want {
+		fmt.Printf("var after range with side-effect = %d want %d\n", k, want)
+		os.Exit(1)
+	}
+}
+
+func checksideeffects() {
+	var x int
+	f := func() int {
+		x++
+		return 0
+	}
+	m := make(map[int]int)
+	m[0] = 0
+	m[1] = 1
+	for k := range m {
+		delete(m, k+f())
+	}
+	if want := 2; x != want {
+		fmt.Printf("var after range with side-effect = %d want %d\n", x, want)
+		os.Exit(1)
+	}
+
+	var n int
+	m = make(map[int]int)
+	m[0] = 0
+	m[1] = 1
+	for k := range m {
+		delete(m, k)
+		n++
+	}
+	if want := 2; n != want {
+		fmt.Printf("counter for range with side-effect = %d want %d\n", n, want)
+		os.Exit(1)
+	}
+}
+
+func main() {
+	checkcleared()
+	checkloopvars()
+	checksideeffects()
+}