diff --git a/corpus/edigits_like.langexp b/corpus/edigits_like.langexp
index b8092b1..83212e6 100644
--- a/corpus/edigits_like.langexp
+++ b/corpus/edigits_like.langexp
@@ -133,7 +133,7 @@ test_k 'n 'k : Int Int -> Bool = {
         (case
           (name_expression
             (name_expression
-              (type
+              (simple_type
                 (simple_type_identifier))
               (simple_name_identifier)
               (number_literal))
@@ -257,13 +257,13 @@ test_k 'n 'k : Int Int -> Bool = {
     (simple_name_identifier)
     (argument_name_identifier)
     (argument_name_identifier)
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
     (block
       (empty_lines)
@@ -280,13 +280,13 @@ test_k 'n 'k : Int Int -> Bool = {
         (return
           (operator_expression
             (name_expression
-              (type
+              (simple_type
                 (simple_type_identifier))
               (simple_name_identifier)
               (number_literal))
             (operator)
             (name_expression
-              (type
+              (simple_type
                 (simple_type_identifier))
               (simple_name_identifier)
               (argument_name_identifier)))))
@@ -355,9 +355,9 @@ test_k 'n 'k : Int Int -> Bool = {
   (function_definition
     (simple_name_identifier)
     (argument_name_identifier)
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
     (block
       (empty_lines)
@@ -450,11 +450,11 @@ test_k 'n 'k : Int Int -> Bool = {
     (simple_name_identifier)
     (argument_name_identifier)
     (argument_name_identifier)
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
     (block
       (empty_lines)
diff --git a/corpus/test.langexp b/corpus/test.langexp
index 0715633..3ce1b98 100644
--- a/corpus/test.langexp
+++ b/corpus/test.langexp
@@ -226,6 +226,12 @@ parse_number : Unit! = {
 : useful when tuples returned
 result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a, 'd := 'b, ());
 
+// (A & B & C) same to Tuple[A B C]
+tuple_argument_test 'x : (A & B & C) = do_something;
+
+// ((A1 & A2) | B | C) same to Variant[Tuple[A1 A2] B C]
+variant_argument_test 'x : ((A1 & A2) | B | C) = do_something;
+
 --------------------------------------------------------------------------------
 
 (source_file
@@ -421,9 +427,9 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
     (simple_name_identifier)
     (argument_name_identifier)
     (annotation_identifier)
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
     (match
       (name_expression
@@ -560,7 +566,7 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
           (simple_name_identifier))
         (case
           (constructor
-            (type
+            (simple_type
               (simple_type_identifier))
             (annotation_identifier)
             (string_literal)
@@ -627,7 +633,7 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
           (simple_name_identifier))
         (case
           (constructor
-            (type
+            (simple_type
               (simple_type_identifier))
             (annotation_identifier)
             (unit_literal))))
@@ -637,21 +643,21 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
           (simple_name_identifier))
         (case
           (constructor
-            (type
+            (simple_type
               (simple_type_identifier))
             (annotation_identifier)
             (unit_literal))
           (string_literal))
         (case
           (constructor
-            (type
+            (simple_type
               (simple_type_identifier))
             (annotation_identifier)
             (unit_literal))
           (string_literal))
         (case
           (constructor
-            (type
+            (simple_type
               (simple_type_identifier))
             (annotation_identifier)
             (unit_literal))
@@ -736,39 +742,35 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
   (empty_lines)
   (type_definition
     (simple_type_identifier)
-    (variant_type
-      (tuple_type
-        (annotation_identifier)
-        (type
-          (simple_type_identifier))
-        (annotation_identifier)
-        (type
-          (simple_type_identifier)))))
+    (tuple_type
+      (annotation_identifier)
+      (simple_type
+        (simple_type_identifier))
+      (annotation_identifier)
+      (simple_type
+        (simple_type_identifier))))
   (empty_lines)
   (type_definition
     (simple_type_identifier)
     (variant_type
-      (tuple_type
-        (annotation_identifier)
-        (type
-          (simple_type_identifier)))
-      (tuple_type
-        (annotation_identifier)
-        (type
-          (simple_type_identifier)))
-      (tuple_type
-        (annotation_identifier)
-        (type
-          (simple_type_identifier)))))
+      (annotation_identifier)
+      (simple_type
+        (simple_type_identifier))
+      (annotation_identifier)
+      (simple_type
+        (simple_type_identifier))
+      (annotation_identifier)
+      (simple_type
+        (simple_type_identifier))))
   (empty_lines)
   (function_definition
     (definition_info
       (info))
     (simple_name_identifier)
     (argument_name_identifier)
-    (type
+    (simple_type
       (simple_type_identifier)
-      (type
+      (simple_type
         (argument_type_identifier)))
     (block
       (empty_lines)
@@ -839,9 +841,9 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
       (info))
     (simple_name_identifier)
     (argument_name_identifier)
-    (type
+    (simple_type
       (simple_type_identifier)
-      (type
+      (simple_type
         (argument_type_identifier)))
     (block
       (empty_lines)
@@ -914,27 +916,28 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
     (simple_type_identifier)
     (argument_type_identifier)
     (argument_type_identifier)
-    (variant_type
-      (tuple_type
-        (annotation_identifier)
-        (type
-          (simple_type_identifier))
-        (annotation_identifier)
-        (type
-          (simple_type_identifier))
-        (annotation_identifier)
-        (type
+    (tuple_type
+      (annotation_identifier)
+      (simple_type
+        (simple_type_identifier))
+      (annotation_identifier)
+      (simple_type
+        (simple_type_identifier))
+      (annotation_identifier)
+      (reference_type
+        (simple_type
           (simple_type_identifier)
-          (type
+          (simple_type
             (argument_type_identifier))
-          (type
-            (argument_type_identifier)))
-        (annotation_identifier)
-        (type
+          (simple_type
+            (argument_type_identifier))))
+      (annotation_identifier)
+      (reference_type
+        (simple_type
           (simple_type_identifier)
-          (type
+          (simple_type
             (argument_type_identifier))
-          (type
+          (simple_type
             (argument_type_identifier))))))
   (empty_lines)
   (function_definition
@@ -975,11 +978,11 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
           (simple_name_identifier))
         (case
           (name_expression
-            (type
+            (simple_type
               (simple_type_identifier)
-              (type
+              (simple_type
                 (simple_type_identifier))
-              (type
+              (simple_type
                 (simple_type_identifier)))
             (simple_name_identifier))))
       (empty_lines)
@@ -988,9 +991,9 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
           (simple_name_identifier))
         (case
           (name_expression
-            (type
+            (simple_type
               (simple_type_identifier)
-              (type
+              (simple_type
                 (simple_type_identifier)))
             (simple_name_identifier))))
       (empty_lines)))
@@ -1076,9 +1079,9 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
     (simple_name_identifier)
     (argument_name_identifier)
     (argument_name_identifier)
-    (type
+    (simple_type
       (argument_type_identifier))
-    (type
+    (simple_type
       (argument_type_identifier))
     (comma_expression
       (comma_expression
@@ -1132,11 +1135,11 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
     (definition_info
       (info))
     (simple_name_identifier)
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
     (operator_expression
       (operator_expression
@@ -1154,7 +1157,7 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
       (info))
     (simple_name_identifier)
     (argument_name_identifier)
-    (type
+    (simple_type
       (simple_type_identifier))
     (match
       (name_expression
@@ -1169,14 +1172,14 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
     (simple_name_identifier)
     (argument_name_identifier)
     (argument_name_identifier)
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
     (constructor
-      (type
+      (simple_type
         (simple_type_identifier))
       (annotation_identifier)
       (argument_name_identifier)
@@ -1189,14 +1192,14 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
     (simple_name_identifier)
     (argument_name_identifier)
     (argument_name_identifier)
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier))
     (constructor
-      (type
+      (simple_type
         (simple_type_identifier))
       (argument_name_identifier)
       (argument_name_identifier)))
@@ -1209,9 +1212,9 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
   (empty_lines)
   (function_definition
     (simple_name_identifier)
-    (type
+    (simple_type
       (simple_type_identifier))
-    (type
+    (simple_type
       (simple_type_identifier)))
   (empty_lines)
   (function_definition
@@ -1238,8 +1241,9 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
     (definition_info
       (info))
     (simple_name_identifier)
-    (type
-      (simple_type_identifier))
+    (modified_type
+      (simple_type
+        (simple_type_identifier)))
     (block
       (empty_lines)
       (match
@@ -1247,7 +1251,7 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
           (simple_name_identifier))
         (case
           (name_expression
-            (type
+            (simple_type
               (simple_type_identifier))
             (simple_name_identifier))))
       (empty_lines)
@@ -1257,7 +1261,7 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
             (simple_name_identifier)))
         (case
           (name_expression
-            (type
+            (simple_type
               (simple_type_identifier))
             (simple_name_identifier)
             (simple_name_identifier))))
@@ -1325,4 +1329,37 @@ result_func! 'a 'b -> 'c -> 'd = ?? 'a == 0 => error "some error" !!=> ('c := 'a
               (name_expression
                 (argument_name_identifier)))))
         (unit_literal))))
+  (empty_lines)
+  (extra)
+  (empty_lines)
+  (function_definition
+    (simple_name_identifier)
+    (argument_name_identifier)
+    (tuple_type
+      (simple_type
+        (simple_type_identifier))
+      (simple_type
+        (simple_type_identifier))
+      (simple_type
+        (simple_type_identifier)))
+    (name_expression
+      (simple_name_identifier)))
+  (empty_lines)
+  (extra)
+  (empty_lines)
+  (function_definition
+    (simple_name_identifier)
+    (argument_name_identifier)
+    (variant_type
+      (tuple_type
+        (simple_type
+          (simple_type_identifier))
+        (simple_type
+          (simple_type_identifier)))
+      (simple_type
+        (simple_type_identifier))
+      (simple_type
+        (simple_type_identifier)))
+    (name_expression
+      (simple_name_identifier)))
   (empty_lines))
diff --git a/grammar.g4 b/grammar.g4
index 1349375..37fcea2 100644
--- a/grammar.g4
+++ b/grammar.g4
@@ -3,6 +3,8 @@ grammar lang ;
 // not always most recent grammar
 // not checked
 
+// TODO
+
 source_file: (statement)+ EOF ;
 
 statement: import
@@ -21,7 +23,7 @@ constraint: '?' expression ;
 function_definition: (definietion_info)? (ANNOTATION_INFO)* (constraint ';')*
                      ('.')? (SIMPLE_NAME_IDENTIFIER | ('(' OPERATOR ')')) ('?' | '!')
                      (((ANNOTATION_IDENTIFIER)? (REFERENCE)? ARGUMENT_NAME_IDENTIFIER ('?' | '!')?)*)
-                     (':' ((ANNOTATION_IDENTIFIER)? (REFERENCE)? type)+)?
+                     (':' ((ANNOTATION_IDENTIFIER)? (REFERENCE)? scoped_type)+)?
                      (('=' ( /*prec 2*/ block | (super_expression ';'))) | ';')
                      ;
 
@@ -29,7 +31,7 @@ type_definition: (DEFINITION_INFO)? (ANNOTATION_INFO)* ('^')?
                  (SIMPLE_TYPE_IDENTIFIER | TYPECLASS_IDENTIFIER)
                  ('[' (TYPECLASS_IDENTIFIER)+ ']')?
                  (ARGUMENT_TYPE_IDENTIFIER)*
-                 ('=' variant_type)?
+                 ('=' type)?
                  ';'
                  ;
 
@@ -76,7 +78,7 @@ loop_control: 'break'
             ;
 
 name_expression:
-  ((type '.' SIMPLE_NAME_IDENTIFIER)
+  ((scoped_type '.' SIMPLE_NAME_IDENTIFIER)
   | (scoped_expression '.' SIMPLE_NAME_IDENTIFIER)
   | name_identifier
   | ('(' OPERATOR ')'))
@@ -84,7 +86,7 @@ name_expression:
   ;
 
 
-constructor: type (ANNOTATION_IDENTIFIER)? scoped_expression)+ ;
+constructor: scoped_type (ANNOTATION_IDENTIFIER)? scoped_expression)+ ;
 
 lambda: '\\' (ARGUMENT_NAME_IDENTIFIER)* '=>' expression ;
 
@@ -121,13 +123,34 @@ not_name_scoped_expression: block
                           | '(' super_expression ')'
                           ;
 
-variant_type: ('|')? tuple_type ('|' tuple_type)* ;
+variant_type: ('|')? annotated_type ('|' annotated_type)+ ;
 
-tuple_type: ('&')? annotated_type ('&' _annotated_type)* ;
+tuple_type: ('&')? annotated_type ('&' _annotated_type)+ ;
 
-annotated_type: (ANNOTATION_IDENTIFIER)? type ;
+annotated_type: (ANNOTATION_IDENTIFIER)? scoped_type ;
 
-type: ('^')? type_identifier ('?')? ('[' (type)+ ']')? ;
+array_type: '[[' type ']]' ;
+
+reference_type: /* prec -1 */ '^' scoped_type ;
+
+modified_type: scoped_type ('?' | '!') ;
+
+simple_type: type_identifier ('[' (scoped_type)+ ']')? ;
+
+type: simple_type
+    | reference_type
+    | modified_type
+    | array_type
+    | variant_type
+    | tuple_type
+    ;
+
+scoped_type: simple_type
+           | reference_type
+           | modified_type
+           | array_type
+           | '(' (variant_type | tuple_type) ')'
+           ;
 
 name_identifier: (ARGUMENT_NAME_IDENTIFIER | SIMPLE_NAME_IDENTIFIER) ;
 type_identifier: (ARGUMENT_TYPE_IDENTIFIER | SIMPLE_TYPE_IDENTIFIER) ;
@@ -152,7 +175,7 @@ EXTRA: EMPTY_LINES
 
 EMPTY_LINES : ('\n')+ ;
 
-LINE_COMMENT : '#!' [^\n]* -> skip ;
+EXEC_COMMENT : '#!' [^\n]* -> skip ;
 LINE_COMMENT : '//' [^\n]* -> skip ;
 BLOCK_COMMENT : '\*' ([^*] |('\*' [^/]))* '*/' -> skip ;
 
diff --git a/grammar.js b/grammar.js
index ee6549f..f808f42 100644
--- a/grammar.js
+++ b/grammar.js
@@ -56,7 +56,7 @@ module.exports = grammar({
         repeat1(seq(
           optional($.annotation_identifier),
           optional($._reference),
-          $.type,
+          $._scoped_type,
         )),
       )),
       choice(seq('=', choice(prec(2, choice($.block, $.array)), seq($._super_expression, ';'))), ';'),
@@ -70,7 +70,7 @@ module.exports = grammar({
       field('name', choice($.simple_type_identifier, $.typeclass_identifier)),
       optional(seq('[', repeat($.typeclass_identifier), ']')), // parametric typeclasses ??
       repeat($.argument_type_identifier), // for datatypes only
-      optional(seq('=', $.variant_type)), // for datatypes only
+      optional(seq('=', $._type)), // for datatypes only
       ';',
     ),
 
@@ -152,7 +152,7 @@ module.exports = grammar({
 
     name_expression: $ => seq(
       choice(
-        seq($.type, '.', field('name', $.simple_name_identifier)),
+        seq($._scoped_type, '.', field('name', $.simple_name_identifier)),
         seq($._scoped_expression, '.', field('name', $.simple_name_identifier)),
         field('name', $._name_identifier),
         seq('(', field('name', $.operator), ')'),
@@ -161,7 +161,7 @@ module.exports = grammar({
     ),
 
     constructor: $ => seq(
-      field('type', $.type),
+      field('type', $._scoped_type),
       repeat1(seq(optional($.annotation_identifier), $._scoped_expression)),
     ),
 
@@ -212,25 +212,54 @@ module.exports = grammar({
 
     // --- type
 
+    // same to Variant[...]
     variant_type: $ => seq(
       optional('|'),
-      $.tuple_type,
-      repeat(seq('|', $.tuple_type)),
+      $._annotated_type,
+      repeat1(seq('|', $._annotated_type)),
     ),
 
+    // same to Tuple[...]
     tuple_type: $ => seq(
       optional('&'),
       $._annotated_type,
-      repeat(seq('&', $._annotated_type)),
+      repeat1(seq('&', $._annotated_type)),
     ),
 
-    _annotated_type: $ => seq(optional($.annotation_identifier), $.type),
+    // add annotations to in all types ??
+    _annotated_type: $ => seq(optional($.annotation_identifier), $._scoped_type),
 
-    type: $ => seq(
-      optional('^'),
+    // same to Array[...]
+    array_type: $ => seq('[[', $._type, ']]'),
+
+    reference_type: $ => prec(-1, seq('^', $._scoped_type)),
+
+    // same to Optional[...] or Result[...]
+    modified_type: $ => seq($._scoped_type, $._optional_or_result),
+
+    simple_type: $ => seq(
       field('name', $._type_identifier),
-      optional($._optional_or_result),
-      optional(seq('[', repeat1($.type), ']'))
+      optional(seq('[', repeat1($._scoped_type), ']'))
+    ),
+
+    _type: $ => choice(
+      $.simple_type,
+      $.reference_type,
+      $.modified_type,
+      $.array_type,
+      $.variant_type,
+      $.tuple_type,
+    ),
+
+    _scoped_type: $ => choice(
+      $.simple_type,
+      $.reference_type,
+      $.modified_type,
+      $.array_type,
+      seq('(', choice(
+        $.variant_type,
+        $.tuple_type,
+      ), ')'),
     ),
 
     // --- comments