analyzer: Support hideConstantImplementations directive

Directive introduced in dart-lang/dartdoc#3398
but not documented yet. Still experimental, but used by Flutter.

Change-Id: I277927a54caf926b0b3d13db589486465ab9358d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/328180
Commit-Queue: Samuel Rawlins <[email protected]>
Reviewed-by: Phil Quitslund <[email protected]>

Author: srawlins

pkg/analyzer/lib/dart/ast/doc_comment.dart

@@ -248,6 +248,10 @@ enum DocDirectiveType {
     ],
   ),
 
+  /// A [DocDirective] indicating that constants should not have their own
+  /// pages or implementations displayed.
+  hideConstantImplementations('hideConstantImplementations'),
+
   /// A [DocDirective] declaring a block of HTML content which is to be inserted
   /// after all other processing, including Markdown parsing.
   ///

pkg/analyzer/lib/src/fasta/doc_comment_builder.dart

@@ -403,6 +403,10 @@ final class DocCommentBuilder {
       case 'example':
         _pushDocDirective(parser.simpleDirective(DocDirectiveType.example));
         return true;
+      case 'hideConstantImplementations':
+        _pushDocDirective(parser
+            .simpleDirective(DocDirectiveType.hideConstantImplementations));
+        return true;
       case 'inject-html':
         _parseBlockDocDirectiveTag(parser, DocDirectiveType.injectHtml);
         return true;

pkg/analyzer/test/src/dart/parser/doc_comment_test.dart

@@ -1109,6 +1109,30 @@ Comment
 ''');
   }
 
+  test_hideConstantImplementations() {
+    final parseResult = parseStringWithErrors(r'''
+int x = 0;
+
+/// Text.
+/// {@hideConstantImplementations}
+class A {}
+''');
+    parseResult.assertNoErrors();
+
+    final node = parseResult.findNode.comment('hideConstantImplementations');
+    assertParsedNodeText(node, r'''
+Comment
+  tokens
+    /// Text.
+    /// {@hideConstantImplementations}
+  docDirectives
+    SimpleDocDirective
+      tag
+        offset: [26, 57]
+        type: [DocDirectiveType.hideConstantImplementations]
+''');
+  }
+
   test_indentedCodeBlock_afterBlankLine() {
     final parseResult = parseStringWithErrors(r'''
 /// Text.