augmentation support for overridden_fields

Fixes: https://github.com/dart-lang/linter/issues/4930

Change-Id: Iee270a59ab3ba76f414a7d743aad92559808a948
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/363640
Commit-Queue: Phil Quitslund <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: pq

pkg/linter/lib/src/rules/overridden_fields.dart

@@ -9,6 +9,7 @@ import 'package:analyzer/dart/element/type.dart';
 import 'package:collection/collection.dart' show IterableExtension;
 
 import '../analyzer.dart';
+import '../extensions.dart';
 
 const _desc = r"Don't override fields.";
 
@@ -128,9 +129,8 @@ class _Visitor extends SimpleAstVisitor<void> {
 
   @override
   void visitFieldDeclaration(FieldDeclaration node) {
-    if (node.isStatic) {
-      return;
-    }
+    if (node.isAugmentation) return;
+    if (node.isStatic) return;
 
     for (var variable in node.fields.variables) {
       var declaredField = variable.declaredElement;

pkg/linter/test/rules/overridden_fields_test.dart

@@ -17,6 +17,65 @@ class OverriddenFieldsTest extends LintRuleTest {
   @override
   String get lintRule => 'overridden_fields';
 
+  test_augmentationClass() async {
+    var a = newFile('$testPackageLibPath/a.dart', r'''
+import augment 'b.dart';
+
+class O {
+  final a = '';
+}
+
+class A extends O { }
+''');
+
+    var b = newFile('$testPackageLibPath/b.dart', r'''
+augment library 'a.dart';
+
+augment class A { 
+  final a = '';
+}
+''');
+
+    result = await resolveFile(a.path);
+    await assertNoDiagnosticsIn(errors);
+
+    result = await resolveFile(b.path);
+    await assertDiagnosticsIn(errors, [
+      lint(54, 1),
+    ]);
+  }
+
+  test_augmentedField() async {
+    var a = newFile('$testPackageLibPath/a.dart', r'''
+import augment 'b.dart';
+
+class O {
+  final a = '';
+}
+
+class A extends O {
+  @override 
+  final a = '';
+}
+''');
+
+    var b = newFile('$testPackageLibPath/b.dart', r'''
+augment library 'a.dart';
+
+augment class A { 
+  augment final a = '';
+}
+''');
+
+    result = await resolveFile(a.path);
+    await assertDiagnosticsIn(errors, [
+      lint(96, 1),
+    ]);
+
+    result = await resolveFile(b.path);
+    await assertNoDiagnosticsIn(errors);
+  }
+
   /// https://github.com/dart-lang/linter/issues/2874
   test_conflictingStaticAndInstance() async {
     await assertNoDiagnostics(r'''