ssa: map delete, map eql nil

cl/_testrt/makemap/in.go

@@ -5,16 +5,32 @@ func main() {
 	m[1] = "hello"
 	m[2] = "world"
 	m[3] = "llgo"
-	println(m[1], m[2], len(m))
+	println(m, m[1], m[2], len(m))
 	for k, v := range m {
 		println(k, ":", v)
 	}
+
 	s := make(map[string]int, len(m))
 	for k, v := range m {
 		s[v] = k
 	}
+
 	id, ok := s["llgo"]
 	println("llgo", id, ok)
+
 	none, ok := s["go"]
 	println("go", none, ok)
+
+	delete(s, "llgo")
+	if _, ok := s["llgo"]; ok {
+		panic("bad key")
+	}
+	if len(s) != 2 {
+		panic("bad len")
+	}
+
+	m2 := make(map[int]string)
+	println(m2, len(m2), m2 == nil, m2 != nil)
+	var m3 map[int]string
+	println(m3, len(m3), m3 == nil, m3 != nil)
 }