Fix method signature validation (#16)

Author: kirillcareem

module.go

@@ -182,16 +182,9 @@ func isError(rt reflect.Type, at int) bool {
 
 func isValid(rt reflect.Type, at int) bool {
 	switch rt.Out(at) {
-	case typeString:
-	case typeNumber:
-	case typeBool:
-	case typeNumbers:
-	case typeStrings:
-	case typeBools:
-	case typeTable:
-	case typeArray:
+	case typeString, typeNumber, typeBool, typeNumbers, typeStrings, typeBools, typeTable, typeArray, typeValue:
+		return true
 	default:
 		return false
 	}
-	return true
 }

module_test.go

@@ -31,6 +31,7 @@ func testModule() Module {
 	must(m.Register("error", errorfunc))
 	must(m.Register("error1", errorfunc1))
 	must(m.Register("toNumbers", toNumbers))
+	must(m.Register("value", value))
 	return m
 }
 
@@ -89,6 +90,10 @@ func toNumbers(v Value) (Numbers, error) {
 	}
 }
 
+func value(v Value) (Value, error) {
+	return v, nil
+}
+
 func Test_Join(t *testing.T) {
 	s, err := newScript("fixtures/join.lua")
 	assert.NoError(t, err)