Fix default type of map created in expr

Author: antonmedv

checker/types.go

@@ -13,7 +13,7 @@ var (
 	floatType     = reflect.TypeOf(float64(0))
 	stringType    = reflect.TypeOf("")
 	arrayType     = reflect.TypeOf([]interface{}{})
-	mapType       = reflect.TypeOf(map[interface{}]interface{}{})
+	mapType       = reflect.TypeOf(map[string]interface{}{})
 	interfaceType = reflect.TypeOf(new(interface{})).Elem()
 )
 

expr_test.go

@@ -637,6 +637,10 @@ func TestExpr(t *testing.T) {
 			`1 + 2 + Three`,
 			6,
 		},
+		{
+			`MapArg({foo: "bar"})`,
+			"bar",
+		},
 	}
 
 	for _, tt := range tests {
@@ -703,6 +707,10 @@ func (*mockEnv) Duration(s string) time.Duration {
 	return d
 }
 
+func (*mockEnv) MapArg(m map[string]interface{}) string {
+	return m["foo"].(string)
+}
+
 type ticket struct {
 	Price int
 }