Handle non-built-in attrs as attr-items

Author: ninevra

grammar.js

@@ -35,6 +35,54 @@ const numeric_types = [
 
 const primitive_types = numeric_types.concat(['bool', 'str', 'char'])
 
+const built_in_attributes = [
+  'cfg',
+  'cfg_attr',
+  'test',
+  'ignore',
+  'should_panic',
+  'derive',
+  'automatically_derived',
+  'macro_export',
+  'macro_use',
+  'proc_macro',
+  'proc_macro_derive',
+  'proc_macro_attribute',
+  'allow',
+  'warn',
+  'deny',
+  'forbid',
+  'deprecated',
+  'must_use',
+  'link',
+  'link_name',
+  'no_link',
+  'repr',
+  'crate_type',
+  'no_main',
+  'export_name',
+  'link_section',
+  'no_mangle',
+  'used',
+  'crate_name',
+  'inline',
+  'cold',
+  'no_builtins',
+  'target_feature',
+  'track_caller',
+  'doc',
+  'no_std',
+  'no_implicit_prelude',
+  'path',
+  'recursion_limit',
+  'type_length_limit',
+  'panic_handler',
+  'global_allocator',
+  'windows_subsystem',
+  'feature',
+  'non_exhaustive'
+]
+
 module.exports = grammar({
   name: 'rust',
 
@@ -205,18 +253,59 @@ module.exports = grammar({
     attribute_item: $ => seq(
       '#',
       '[',
-      $.meta_item,
+      $._attr,
       ']'
     ),
 
     inner_attribute_item: $ => seq(
       '#',
       '!',
       '[',
-      $.meta_item,
+      $._attr,
       ']'
     ),
 
+    _attr: $ => choice(
+      alias($.built_in_attr, $.meta_item),
+      alias($.custom_attr, $.attr_item),
+    ),
+
+    custom_attr: $ => seq(
+      $._path,
+      optional(choice(
+        seq('=', field('value', $._literal)),
+        field('arguments', $.delim_token_tree)
+      ))
+    ),
+
+    delim_token_tree: $ => choice(
+      seq('(', repeat($._delim_tokens), ')'),
+      seq('[', repeat($._delim_tokens), ']'),
+      seq('{', repeat($._delim_tokens), '}')
+    ),
+
+    _delim_tokens: $ => choice(
+      $._non_delim_token,
+      $.delim_token_tree,
+    ),
+
+    _non_delim_token: $ => choice(
+      $._non_special_token,
+      '$'
+    ),
+
+    built_in_attr: $ => seq(
+      $._built_in_attr_path,
+      optional(choice(
+        seq('=', field('value', $._literal)),
+        field('arguments', $.meta_arguments)
+      ))
+    ),
+
+    _built_in_attr_path: $ => choice(
+      ...built_in_attributes.map(name => alias(name, $.identifier))
+    ),
+
     meta_item: $ => seq(
       $._path,
       optional(choice(