3 files changed, 68 insertions, 0 deletions
diff --git a/main_test.go b/main_test.go
index 3b088ada8..01835a2c6 100644
--- a/main_test.go
+++ b/main_test.go
@@ -57,6 +57,7 @@ func TestBuild(t *testing.T) {
 		"json.go",
 		"map.go",
 		"math.go",
+		"mapgrowth.go",
 		"print.go",
 		"reflect.go",
 		"slice.go",
diff --git a/testdata/mapgrowth.go b/testdata/mapgrowth.go
new file mode 100644
index 000000000..5a37303af
--- /dev/null
+++ b/testdata/mapgrowth.go
@@ -0,0 +1,66 @@
+package main
+
+func main() {
+
+	m := make(map[int]int)
+
+	const (
+		Delete = 500
+		N      = Delete * 2
+	)
+
+	for i := 0; i < Delete; i++ {
+		m[i] = i
+	}
+
+	var deleted bool
+	for k, v := range m {
+		if k == 0 {
+			// grow map
+			for i := Delete; i < N; i++ {
+				m[i] = i
+			}
+
+			// delete some elements
+			for i := 0; i < Delete; i++ {
+				delete(m, i)
+			}
+			deleted = true
+			continue
+		}
+
+		// make sure we never see a deleted element later in our iteration
+		if deleted && v < Delete {
+			println("saw deleted element", v)
+		}
+	}
+
+	if len(m) != N-Delete {
+		println("bad length post grow/delete", len(m))
+	}
+
+	seen := make([]bool, 500)
+
+	var mcount int
+	for k, v := range m {
+		if k != v {
+			println("element mismatch", k, v)
+		}
+		if k < Delete {
+			println("saw deleted element post-grow", k)
+		}
+		seen[v-Delete] = true
+		mcount++
+	}
+
+	for _, v := range seen {
+		if !v {
+			println("missing key", v)
+		}
+	}
+
+	if mcount != N-Delete {
+		println("bad number of elements post-grow:", mcount)
+	}
+	println("done")
+}
diff --git a/testdata/mapgrowth.txt b/testdata/mapgrowth.txt
new file mode 100644
index 000000000..19f86f493
--- /dev/null
+++ b/testdata/mapgrowth.txt
@@ -0,0 +1 @@
+done