[analysis_server] Add occurrences/document highlights for type aliases

Fixes #56994

Change-Id: I0721603b7b019ab09614265e412d3b9e76d26ad9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/392660
Reviewed-by: Phil Quitslund <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Phil Quitslund <[email protected]>

Author: DanTup

pkg/analysis_server/lib/src/domains/analysis/occurrences_dart.dart

@@ -41,6 +41,13 @@ class _DartUnitOccurrencesComputerVisitor extends RecursiveAstVisitor<void> {
     super.visitClassDeclaration(node);
   }
 
+  @override
+  void visitClassTypeAlias(ClassTypeAlias node) {
+    _addOccurrence(node.declaredElement!, node.name.offset);
+
+    super.visitClassTypeAlias(node);
+  }
+
   @override
   void visitConstructorDeclaration(ConstructorDeclaration node) {
     if (node.name case var name?) {
@@ -104,6 +111,20 @@ class _DartUnitOccurrencesComputerVisitor extends RecursiveAstVisitor<void> {
     super.visitFunctionDeclaration(node);
   }
 
+  @override
+  void visitFunctionTypeAlias(FunctionTypeAlias node) {
+    _addOccurrence(node.declaredElement!, node.name.offset);
+
+    super.visitFunctionTypeAlias(node);
+  }
+
+  @override
+  void visitGenericTypeAlias(GenericTypeAlias node) {
+    _addOccurrence(node.declaredElement!, node.name.offset);
+
+    super.visitGenericTypeAlias(node);
+  }
+
   @override
   void visitMethodDeclaration(MethodDeclaration node) {
     _addOccurrence(node.declaredElement!, node.name.offset);

pkg/analysis_server/test/lsp/document_highlights_test.dart

@@ -193,6 +193,42 @@ void f() {
   print(/*[1*/_/*1]*/);
   /*[2*/^_/*2]*/ = '';
 }
+''');
+
+  Future<void> test_typeAlias_class_declaration() => _testMarkedContent('''
+class MyClass {}
+mixin MyMixin {}
+class /*[0*/MyAli^as/*0]*/ = MyClass with MyMixin;
+/*[1*/MyAlias/*1]*/? a;
+''');
+
+  Future<void> test_typeAlias_class_reference() => _testMarkedContent('''
+class MyClass {}
+mixin MyMixin {}
+class /*[0*/MyAlias/*0]*/ = MyClass with MyMixin;
+/*[1*/MyAl^ias/*1]*/? a;
+''');
+
+  Future<void> test_typeAlias_function_declaration() => _testMarkedContent('''
+typedef /*[0*/myFu^nc/*0]*/();
+/*[1*/myFunc/*1]*/? f;
+''');
+
+  Future<void> test_typeAlias_function_reference() => _testMarkedContent('''
+typedef /*[0*/myFunc/*0]*/();
+/*[1*/myFun^c/*1]*/? f;
+''');
+
+  Future<void> test_typeAlias_generic_declaration() => _testMarkedContent('''
+typedef /*[0*/TD^/*0]*/ = String;
+
+/*[1*/TD/*1]*/? a;
+''');
+
+  Future<void> test_typeAlias_generic_reference() => _testMarkedContent('''
+typedef /*[0*/TD/*0]*/ = String;
+
+/*[1*/TD^/*1]*/? a;
 ''');
 
   /// Tests highlights in a Dart file using the provided content.