Fix for create constructor for Widget with private fields.

Fixes https://github.com/dart-lang/sdk/issues/56182

Change-Id: I25a94dbb5af5dda4db1fde9494783df215587fd5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/410520
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Keerti Parthasarathy <keertip@google.com>

pkg/analysis_server/lib/src/services/correction/dart/create_constructor_for_final_fields.dart

@@ -174,13 +174,19 @@ class CreateConstructorForFinalFields extends ResolvedCorrectionProducer {
           ),
         );
         builder.write(' key');
+        var fieldsForInitializers = <_Field>[];
 
         _writeFlutterParameters(
           builder: builder,
           variableLists: fixContext.variableLists,
+          fieldsForInitializers: fieldsForInitializers,
         );
 
-        builder.write('}) : super(key: key);');
+        builder.write('}) : ');
+        if (fieldsForInitializers.isNotEmpty) {
+          builder.write('${_getInitalizersString(fieldsForInitializers)}, ');
+        }
+        builder.write('super(key: key);');
       });
     });
   }
@@ -198,16 +204,29 @@ class CreateConstructorForFinalFields extends ResolvedCorrectionProducer {
         builder.write('({');
         builder.write('super.key');
 
+        var fieldsForInitializers = <_Field>[];
         _writeFlutterParameters(
           builder: builder,
           variableLists: fixContext.variableLists,
+          fieldsForInitializers: fieldsForInitializers,
         );
 
-        builder.write('});');
+        builder.write('})');
+        if (fieldsForInitializers.isNotEmpty) {
+          builder.write(' : ${_getInitalizersString(fieldsForInitializers)}');
+        }
+        builder.write(';');
       });
     });
   }
 
+  String _getInitalizersString(List<_Field> fieldsForInitializers) =>
+      fieldsForInitializers
+          .map((field) {
+            return '${field.fieldName} = ${field.namedFormalParameterName}';
+          })
+          .join(', ');
+
   Future<void> _notFlutterNamed({
     required _FixContext fixContext,
     required NamedCompilationUnitMember containerDeclaration,
@@ -259,12 +278,7 @@ class CreateConstructorForFinalFields extends ResolvedCorrectionProducer {
         builder.write('})');
 
         if (fieldsForInitializers.isNotEmpty) {
-          var code = fieldsForInitializers
-              .map((field) {
-                return '${field.fieldName} = ${field.namedFormalParameterName}';
-              })
-              .join(', ');
-          builder.write(' : $code');
+          builder.write(' : ${_getInitalizersString(fieldsForInitializers)}');
         }
 
         builder.write(';');
@@ -332,6 +346,7 @@ class CreateConstructorForFinalFields extends ResolvedCorrectionProducer {
   void _writeFlutterParameters({
     required DartEditBuilder builder,
     required Iterable<VariableDeclarationList> variableLists,
+    required List<_Field> fieldsForInitializers,
   }) {
     var fields = _fieldsToWrite(variableLists);
     if (fields == null) {
@@ -345,8 +360,15 @@ class CreateConstructorForFinalFields extends ResolvedCorrectionProducer {
       if (field.hasNonNullableType) {
         builder.write('required ');
       }
-      builder.write('this.');
-      builder.write(field.fieldName);
+      if (field.namedFormalParameterName == field.fieldName) {
+        builder.write('this.');
+        builder.write(field.fieldName);
+      } else {
+        builder.write(utils.getNodeText(field.typeAnnotation));
+        builder.write(' ');
+        builder.write(field.namedFormalParameterName);
+        fieldsForInitializers.add(field);
+      }
     }
   }
 }

pkg/analysis_server/test/src/services/correction/fix/create_constructor_for_final_fields_test.dart

@@ -46,6 +46,31 @@ class Test {
 ''');
   }
 
+  Future<void> test_class_flutter() async {
+    writeTestPackageConfig(flutter: true);
+    await resolveTestCode('''
+import 'package:flutter/widgets.dart';
+
+class Test extends StatelessWidget {
+  final int _a;
+}
+''');
+    await assertHasFix(
+      '''
+import 'package:flutter/widgets.dart';
+
+class Test extends StatelessWidget {
+  final int _a;
+
+  const Test({super.key, required int a}) : _a = a;
+}
+''',
+      errorFilter: (error) {
+        return error.message.contains("'_a' must be initialized");
+      },
+    );
+  }
+
   Future<void> test_class_hasSuperClass_withOptionalNamed() async {
     await resolveTestCode('''
 class A {
@@ -556,4 +581,31 @@ class MyWidget extends StatelessWidget {
       },
     );
   }
+
+  Future<void> test_class_flutter_private_field() async {
+    writeTestPackageConfig(flutter: true);
+    await resolveTestCode('''
+import 'package:flutter/widgets.dart';
+
+class MyWidget extends StatelessWidget {
+  final int _a;
+  final int b;
+}
+''');
+    await assertHasFix(
+      '''
+import 'package:flutter/widgets.dart';
+
+class MyWidget extends StatelessWidget {
+  final int _a;
+  final int b;
+
+  const MyWidget({Key? key, required int a, required this.b}) : _a = a, super(key: key);
+}
+''',
+      errorFilter: (error) {
+        return error.message.contains("'b'");
+      },
+    );
+  }
 }