[analysis_server] Tweak handling of factory keyword without type names in constructors

Change-Id: I4d162ef66300caa07fd64f7de338c6ed1df04fc1
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/481963
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>

pkg/analysis_server/lib/src/computer/computer_highlights.dart

@@ -917,6 +917,16 @@ class _DartUnitHighlightsComputerVisitor extends RecursiveAstVisitor<void> {
     computer._addRegion_token(
       node.factoryKeyword,
       HighlightRegionType.BUILT_IN,
+      // We mark the factory keyword as the declaration when there is no
+      // type name (otherwise the type name is the declaration). This will allow
+      // the client/user to customise these differently if they wish, like they
+      // can with methods / constructors.
+      semanticTokenModifiers: node.typeName != null
+          ? null
+          : {
+              CustomSemanticTokenModifiers.constructor,
+              SemanticTokenModifiers.declaration,
+            },
     );
     computer._addRegion_token(node.constKeyword, HighlightRegionType.KEYWORD);
     computer._addRegion_token(

pkg/analysis_server/test/analysis/notification_highlights2_test.dart

@@ -689,6 +689,25 @@ Never nnn() => throw '';
     assertHasRegion(HighlightRegionType.CLASS, 'Never nnn');
   }
 
+  Future<void> test_class_constructor_factoryKeyword() async {
+    var testCode = TestCode.parseNormalized(r'''
+class A {
+  A._();
+[!
+  factory () {}
+  factory named() {}
+!]
+}
+''');
+    addTestFile(testCode.code);
+    await prepareHighlights();
+    assertHighlightText(testCode, 0, r'''
+4:3 |factory| BUILT_IN
+5:3 |factory| BUILT_IN
+5:11 |named| CONSTRUCTOR
+''');
+  }
+
   Future<void> test_class_constructor_fieldFormalParameter() async {
     var testCode = TestCode.parseNormalized(r'''
 class A {
@@ -710,7 +729,7 @@ class A {
 ''');
   }
 
-  Future<void> test_class_constructor_new() async {
+  Future<void> test_class_constructor_newKeyword() async {
     var testCode = TestCode.parseNormalized(r'''
 class A {
 [!

pkg/analysis_server/test/lsp/semantic_tokens_test.dart

@@ -550,6 +550,39 @@ const e = const MyClass();
     await _initializeAndVerifyTokens(content, expected);
   }
 
+  Future<void> test_class_constructors_factoryKeyword() async {
+    var content = r'''
+class A {
+  A._();
+[!
+  factory() => A._();
+  factory named() => A._();
+!]
+}
+''';
+
+    var expected = [
+      _Token('factory', .keyword, [
+        CustomSemanticTokenModifiers.constructor,
+        .declaration,
+      ]),
+      _Token('A', .class_, [CustomSemanticTokenModifiers.constructor]),
+      _Token('_', .method, [CustomSemanticTokenModifiers.constructor]),
+      _Token('factory', .keyword, [
+        CustomSemanticTokenModifiers.constructor,
+        .declaration,
+      ]),
+      _Token('named', .method, [
+        CustomSemanticTokenModifiers.constructor,
+        .declaration,
+      ]),
+      _Token('A', .class_, [CustomSemanticTokenModifiers.constructor]),
+      _Token('_', .method, [CustomSemanticTokenModifiers.constructor]),
+    ];
+
+    await _initializeAndVerifyTokensInRange(content, expected);
+  }
+
   Future<void> test_class_constructors_newKeyword() async {
     var content = r'''
 class A {