Allow 'default' and 'union' in paths (#77)

* Allow 'default' and 'union' in paths

* And allow them as macro identifiers

* Add a test for macros default! and union!

corpus/declarations.txt

@@ -1384,3 +1384,21 @@ crate const X: u32 = 0;
     (visibility_modifier (crate)) (identifier) (parameters) (block))
   (const_item
     (visibility_modifier (crate)) (identifier) (primitive_type) (integer_literal)))
+
+===================================
+Reserved keywords in path
+===================================
+
+struct A {
+  a: default::B,
+  b: union::C,
+}
+
+---
+
+(source_file
+  (struct_item
+    (type_identifier)
+      (field_declaration_list
+        (field_declaration (field_identifier) (scoped_type_identifier (identifier) (type_identifier)))
+        (field_declaration (field_identifier) (scoped_type_identifier (identifier) (type_identifier))))))

corpus/macros.txt

@@ -28,6 +28,8 @@ a!(b + c + +);
 a!('a'..='z');
 a!('\u{0}'..='\u{2}');
 a!('lifetime)
+default!(a);
+union!(a);
 
 ----
 
@@ -50,6 +52,12 @@ a!('lifetime)
   (macro_invocation
     (identifier)
     (token_tree (char_literal) (char_literal)))
+  (macro_invocation
+    (identifier)
+    (token_tree (identifier)))
+  (macro_invocation
+    (identifier)
+    (token_tree (identifier)))
   (macro_invocation
     (identifier)
     (token_tree (identifier))))

grammar.js

@@ -129,7 +129,10 @@ module.exports = grammar({
 
       return seq(
         'macro_rules!',
-        field('name', $.identifier),
+        field('name', choice(
+          $.identifier,
+          $._reserved_identifier,
+        )),
         choice(
           seq('(', rules, ')', ';'),
           seq('{', rules, '}')
@@ -877,7 +880,8 @@ module.exports = grammar({
     macro_invocation: $ => seq(
       field('macro', choice(
         $.scoped_identifier,
-        $.identifier
+        $.identifier,
+        $._reserved_identifier,
       )),
       '!',
       $.token_tree
@@ -1429,7 +1433,8 @@ module.exports = grammar({
       $.super,
       $.crate,
       $.identifier,
-      $.scoped_identifier
+      $.scoped_identifier,
+      $._reserved_identifier,
     ),
 
     identifier: $ => /(r#)?[_\p{XID_Start}][_\p{XID_Continue}]*/,
@@ -1445,7 +1450,7 @@ module.exports = grammar({
     self: $ => 'self',
     super: $ => 'super',
     crate: $ => 'crate',
-
+    
     metavariable: $ => /\$[a-zA-Z_]\w*/
   }
 })

src/grammar.json

@@ -152,8 +152,17 @@
           "type": "FIELD",
           "name": "name",
           "content": {
-            "type": "SYMBOL",
+            "type": "CHOICE",
-            "name": "identifier"
+            "members": [
+              {
+                "type": "SYMBOL",
+                "name": "identifier"
+              },
+              {
+                "type": "SYMBOL",
+                "name": "_reserved_identifier"
+              }
+            ]
           }
         },
         {
@@ -4852,6 +4861,10 @@
               {
                 "type": "SYMBOL",
                 "name": "identifier"
+              },
+              {
+                "type": "SYMBOL",
+                "name": "_reserved_identifier"
               }
             ]
           }
@@ -8213,6 +8226,10 @@
         {
           "type": "SYMBOL",
           "name": "scoped_identifier"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_reserved_identifier"
         }
       ]
     },