Fine. Add ElementImpl.firstFragmentLocation to avoid opaque requirements

Building context messages needs the element’s name location, but calling
`firstFragment` records an opaque API-use requirement. This patch adds a
specialized accessor that exposes only the needed fields so diagnostics
can be produced without introducing spurious dependencies.

Changes:
- Introduce `ElementImpl.firstFragmentLocation`, returning a lightweight
  `FirstFragmentLocation` with `libraryFragment`, `name`, and
  `nameOffset`, without recording an opaque requirement.
- Update `base_or_final_type_verifier.dart` to build the context message
  from `firstFragmentLocation` instead of `firstFragment`.

This is intended to preserve diagnostic behavior while avoiding opaque
requirement tracking and the follow-on rebuilds it can cause.

Found with https://dart-review.googlesource.com/c/sdk/+/446480

Change-Id: I096091cd030824cbd8794f4063b963672056da29
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/446562
Reviewed-by: Paul Berry <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov

pkg/analyzer/lib/src/dart/element/element.dart

@@ -1699,6 +1699,16 @@ abstract class ElementImpl implements Element {
     return buffer.toString();
   }
 
+  /// The location of [firstFragment], without recording opaque requirement.
+  @trackedIncludedInId
+  FirstFragmentLocation get firstFragmentLocation {
+    return FirstFragmentLocation(
+      libraryFragment: _firstFragment.libraryFragment,
+      name: _firstFragment.name,
+      nameOffset: _firstFragment.nameOffset,
+    );
+  }
+
   @override
   List<Fragment> get fragments {
     return [
@@ -2877,6 +2887,19 @@ class FieldFragmentImpl extends PropertyInducingFragmentImpl
   }
 }
 
+/// Location information extracted from [Element.firstFragment].
+class FirstFragmentLocation {
+  final LibraryFragmentImpl? libraryFragment;
+  final String? name;
+  final int? nameOffset;
+
+  FirstFragmentLocation({
+    required this.libraryFragment,
+    required this.name,
+    required this.nameOffset,
+  });
+}
+
 class FormalParameterElementImpl extends PromotableElementImpl
     with InternalFormalParameterElement {
   @override

pkg/analyzer/lib/src/error/base_or_final_type_verifier.dart

@@ -208,10 +208,13 @@ class BaseOrFinalTypeVerifier {
       return false;
     }
 
-    var fragment = baseOrFinalSuperElement.firstFragment;
-    var fragmentName = fragment.name;
-    var fragmentNameOffset = fragment.nameOffset;
-    if (fragmentName == null || fragmentNameOffset == null) {
+    var superLocation = baseOrFinalSuperElement.firstFragmentLocation;
+    var superLibraryFragment = superLocation.libraryFragment;
+    var superName = superLocation.name;
+    var superNameOffset = superLocation.nameOffset;
+    if (superLibraryFragment == null ||
+        superName == null ||
+        superNameOffset == null) {
       return false;
     }
 
@@ -220,13 +223,13 @@ class BaseOrFinalTypeVerifier {
     // an induced modifier of the direct super element.
     var contextMessages = <DiagnosticMessage>[
       DiagnosticMessageImpl(
-        filePath: fragment.libraryFragment.source.fullName,
-        length: fragmentName.length,
+        filePath: superLibraryFragment.source.fullName,
+        length: superName.length,
         message:
             "The type '${superElement.displayName}' is a subtype of "
             "'${baseOrFinalSuperElement.displayName}', and "
             "'${baseOrFinalSuperElement.displayName}' is defined here.",
-        offset: fragmentNameOffset,
+        offset: superNameOffset,
         url: null,
       ),
     ];

pkg/analyzer/test/src/dart/analysis/driver_test.dart

@@ -27019,6 +27019,91 @@ mixin A {
     );
   }
 
+  test_dependency_notOpaque_baseClassImplementedOutsideOfLibrary() async {
+    configuration.withStreamResolvedUnitResults = false;
+    await _runChangeScenarioTA(
+      initialA: r'''
+base class A {}
+''',
+      testCode: r'''
+import 'a.dart';
+base class X implements A {}
+''',
+      operation: _FineOperationTestFileGetErrors(),
+      expectedInitialEvents: r'''
+[status] working
+[operation] linkLibraryCycle SDK
+[future] getErrors T1
+  ErrorsResult #0
+    path: /home/test/lib/test.dart
+    uri: package:test/test.dart
+    flags: isLibrary
+    errors
+      41 +1 INVALID_USE_OF_TYPE_OUTSIDE_LIBRARY
+[operation] linkLibraryCycle
+  package:test/a.dart
+    declaredClasses
+      A: #M0
+        interface: #M1
+  requirements
+[operation] linkLibraryCycle
+  package:test/test.dart
+    declaredClasses
+      X: #M2
+        interface: #M3
+  requirements
+    libraries
+      package:test/a.dart
+        exportedTopLevels
+          A: #M0
+        interfaces
+          A
+            interfaceId: #M1
+[operation] analyzeFile
+  file: /home/test/lib/test.dart
+  library: /home/test/lib/test.dart
+[operation] analyzedLibrary
+  file: /home/test/lib/test.dart
+  requirements
+    libraries
+      package:test/a.dart
+        exportedTopLevels
+          A: #M0
+        instances
+          A
+[status] idle
+''',
+      updatedA: r'''
+base class A {}
+class B {}
+''',
+      expectedUpdatedEvents: r'''
+[status] working
+[operation] linkLibraryCycle
+  package:test/a.dart
+    declaredClasses
+      A: #M0
+        interface: #M1
+      B: #M4
+        interface: #M5
+  requirements
+[future] getErrors T2
+  ErrorsResult #1
+    path: /home/test/lib/test.dart
+    uri: package:test/test.dart
+    flags: isLibrary
+    errors
+      41 +1 INVALID_USE_OF_TYPE_OUTSIDE_LIBRARY
+[operation] readLibraryCycleBundle
+  package:test/test.dart
+[operation] getErrorsFromBytes
+  file: /home/test/lib/test.dart
+  library: /home/test/lib/test.dart
+[status] idle
+''',
+    );
+  }
+
   test_dependency_opaqueApiUse_firstFragment() async {
     _ManualRequirements.install((state) {
       var A = state.singleUnit.scopeInterfaceElement('A');