enh(dart) highlight built-in nullable types (#2598)

* Dart: allow built-in nullable types with trailing ? to be highlighted

CHANGES.md

@@ -44,7 +44,7 @@ Language Improvements:
 - fix(typescript) `=>` function with nested `()` in params now works (#2502) [Josh Goebel][]
 - fix(yaml) Fix tags to include non-word characters (#2486) [Peter Plantinga][]
 - fix(swift) `@objcMembers` was being partially highlighted (#2543) [Nick Randall][]
-- enh(dart) Add `late` and `required` keywords, and `Never` built-in type (#2550) [Sam Rawlins][]
+- enh(dart) Add `late` and `required` keywords, the `Never` built-in type, and nullable built-in types (#2550) [Sam Rawlins][]
 - enh(erlang) Add underscore separators to numeric literals (#2554) [Sergey Prokhorov][]
 - enh(handlebars) Support for sub-expressions, path-expressions, hashes, block-parameters and literals (#2344) [Nils Knappmeier][]
 - enh(protobuf) Support multiline comments (#2597) [Pavel Evstigneev][]

src/languages/dart.js

@@ -8,23 +8,23 @@ Category: scripting
 */
 
 export default function(hljs) {
- var SUBST = {
+ const SUBST = {
  className: 'subst',
  variants: [{
  begin: '\\$[A-Za-z0-9_]+'
  }],
  };
 
- var BRACED_SUBST = {
+ const BRACED_SUBST = {
  className: 'subst',
  variants: [{
  begin: '\\${',
  end: '}'
- }, ],
+ }],
  keywords: 'true false null this is new super',
  };
 
- var STRING = {
+ const STRING = {
  className: 'string',
  variants: [{
  begin: 'r\'\'\'',
@@ -72,17 +72,59 @@ export default function(hljs) {
  hljs.C_NUMBER_MODE, STRING
  ];
 
- var KEYWORDS = {
+ const BUILT_IN_TYPES = [
+ // dart:core
+ 'Comparable',
+ 'DateTime',
+ 'Duration',
+ 'Function',
+ 'Iterable',
+ 'Iterator',
+ 'List',
+ 'Map',
+ 'Match',
+ 'Object',
+ 'Pattern',
+ 'RegExp',
+ 'Set',
+ 'Stopwatch',
+ 'String',
+ 'StringBuffer',
+ 'StringSink',
+ 'Symbol',
+ 'Type',
+ 'Uri',
+ 'bool',
+ 'double',
+ 'int',
+ 'num',
+ // dart:html
+ 'Element',
+ 'ElementList',
+ ];
+ const NULLABLE_BUILT_IN_TYPES = BUILT_IN_TYPES.map((e) => `${e}?`);
+
+ const KEYWORDS = {
  keyword: 'abstract as assert async await break case catch class const continue covariant default deferred do ' +
  'dynamic else enum export extends extension external factory false final finally for Function get hide if ' +
  'implements import in inferface is late library mixin new null on operator part required rethrow return set ' +
  'show static super switch sync this throw true try typedef var void while with yield',
  built_in:
- // dart:core
- 'Comparable DateTime Duration Function Iterable Iterator List Map Match Never Null Object Pattern RegExp ' +
- 'Set Stopwatch String StringBuffer StringSink Symbol Type Uri bool double dynamic int num print ' +
- // dart:html
- 'Element ElementList document querySelector querySelectorAll window'
+ BUILT_IN_TYPES
+ .concat(NULLABLE_BUILT_IN_TYPES)
+ .concat([
+ // dart:core
+ 'Never',
+ 'Null',
+ 'dynamic',
+ 'print',
+ // dart:html
+ 'document',
+ 'querySelector',
+ 'querySelectorAll',
+ 'window',
+ ]).join(' '),
+ $pattern: /[A-Za-z][A-Za-z0-9_]*\??/
  };
 
  return {
@@ -130,5 +172,5 @@ export default function(hljs) {
  begin: '=>' // No markup, just a relevance booster
  }
  ]
- }
+ };
 }