[DAS] Fixes dot-shorthands completion for enum constant creation

Fixes: #62168
Change-Id: I435835016e5c213deab3f9979dd554d06cd40fa6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/466140
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Kallen Tu <kallentu@google.com>
Commit-Queue: Kallen Tu <kallentu@google.com>
Auto-Submit: Felipe Morschel <git@fmorschel.dev>

Author: FMorschel

pkg/analysis_server/lib/src/services/completion/dart/feature_computer.dart

@@ -1430,6 +1430,10 @@ extension on ArgumentList {
       if (parent.element case ConstructorElement constructorElement) {
         return constructorElement.type;
       }
+    } else if (parent is EnumConstantArguments) {
+      if (parent.parent case EnumConstantDeclaration enumConstantDeclaration) {
+        return enumConstantDeclaration.constructorElement?.type;
+      }
     }
     return null;
   }

pkg/analysis_server/test/services/completion/dart/declaration/enum_test.dart

@@ -301,6 +301,26 @@ suggestions
 ''');
   }
 
+  Future<void> test_dotShorthand_onDeclaration() async {
+    await computeSuggestions('''
+enum E0 {
+  c0,
+  c1(.^);
+
+  const E0([E0? other]);
+}
+''');
+    assertResponse(r'''
+suggestions
+  c0
+    kind: enumConstant
+  c1
+    kind: enumConstant
+  values
+    kind: field
+''');
+  }
+
   Future<void> test_enumConstantName() async {
     await _check_locations(
       declaration: '''

pkg/analysis_server/test/src/services/completion/dart/feature_computer_test.dart

@@ -505,6 +505,17 @@ void f() {
 ''', 'String');
   }
 
+  Future<void> test_dotShorthand_enumConstantCreation() async {
+    await assertContextType('''
+enum E0 {
+  c0,
+  c1(.^);
+
+  const E0([E0? other]);
+}
+''', 'E0?');
+  }
+
   Future<void> test_dotShorthand_guardedPattern_switchExpression() async {
     await assertContextType('''
 enum E { a }