[DAS] Fixes record extension field completion

Bug: https://github.com/dart-lang/sdk/issues/60625
Change-Id: I23e4a5a85dc15059c9b1e658fb2fc3f868fa91a7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/424684
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Auto-Submit: Felipe Morschel <git@fmorschel.dev>

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

@@ -1317,6 +1317,8 @@ class DeclarationHelper {
         includeMethods: true,
         includeSetters: true,
       );
+    } else if (thisType is RecordType) {
+      _addFieldsOfRecordType(type: thisType, excludedFields: {});
     }
   }
 

pkg/analysis_server/test/services/completion/dart/location/extension_body_test.dart

@@ -125,6 +125,20 @@ suggestions
 ''');
   }
 
+  Future<void> test_inMethod_namedRecordFields() async {
+    allowedIdentifiers = {'value1'};
+    await computeSuggestions('''
+extension E on ({int value1,}) {foo() {  val^;} }
+''');
+    assertResponse(r'''
+replacement
+  left: 3
+suggestions
+  value1
+    kind: identifier
+''');
+  }
+
   Future<void> test_inMethod_parameterShadowField() async {
     allowedIdentifiers = {'aaa'};
     await computeSuggestions('''
@@ -142,6 +156,22 @@ suggestions
     kind: parameter
   assert
     kind: keyword
+''');
+  }
+
+  Future<void> test_inMethod_positionalRecordFields() async {
+    allowedIdentifiers = {r'$1', r'$2'};
+    await computeSuggestions(r'''
+extension E on (int, String,) {foo() {  $^;} }
+''');
+    assertResponse(r'''
+replacement
+  left: 1
+suggestions
+  $1
+    kind: identifier
+  $2
+    kind: identifier
 ''');
   }
 }