Add a new fix for representationFieldModifier

This add a fix to add a type annotation in place of the `var` keyword.

The assist to add a type annotation was already being offered, but it
didn't understand that it needed to also remove the keyword. The added
fix will do both, and, by being a fix, will appear higher in the list
of code actions that users see, along side the fix to remove the
keyword without adding a type annotation.

The fix to remove the keyword can be bulk applied, so I couldn't make
the new one also be bulk applicable. We might consider reversing the
status so that the default bulk fix behavior includes adding a type
annotation, but this CL doesn't do that.

Change-Id: I122221ef1e5119a76e1157a9a15cf1193135fc59
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/507161
Reviewed-by: Samuel Rawlins <srawlins@google.com>

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

@@ -21,14 +21,25 @@ class AddTypeAnnotation extends ResolvedCorrectionProducer {
   @override
   final CorrectionApplicability applicability;
 
+  final bool forRepresentationField;
+
   /// Initializes a newly created instance that can't apply bulk and in-file
   /// fixes.
   new({required super.context})
-    : applicability = CorrectionApplicability.singleLocation;
+    : applicability = CorrectionApplicability.singleLocation,
+      forRepresentationField = false;
 
-  /// Initializes a newly created instance that can apply bulk and in-file fixes.
+  /// Initializes a newly created instance that can apply bulk and in-file
+  /// fixes.
   new bulkFixable({required super.context})
-    : applicability = CorrectionApplicability.automatically;
+    : applicability = CorrectionApplicability.automatically,
+      forRepresentationField = false;
+
+  /// Initializes a newly created instance that will replace the keyword with
+  /// the added type.
+  new forRepresentationField({required super.context})
+    : applicability = CorrectionApplicability.singleLocation,
+      forRepresentationField = true;
 
   @override
   AssistKind get assistKind => DartAssistKind.addTypeAnnotation;
@@ -92,7 +103,8 @@ class AddTypeAnnotation extends ResolvedCorrectionProducer {
   ) async {
     await builder.addDartFileEdit(file, (builder) {
       if (builder.canWriteType(type, offset: name.offset)) {
-        if (keyword != null && keyword.keyword == Keyword.VAR) {
+        if (keyword != null &&
+            (forRepresentationField || keyword.keyword == Keyword.VAR)) {
           builder.addReplacement(range.token(keyword), (builder) {
             builder.writeType(type);
           });
@@ -137,7 +149,7 @@ class AddTypeAnnotation extends ResolvedCorrectionProducer {
     if (parameter.type != null) {
       return;
     }
-    // Ensure that the parameter is named.
+    // Ensure that the parameter has a named.
     var name = parameter.name;
     if (name == null) {
       return;
@@ -145,15 +157,18 @@ class AddTypeAnnotation extends ResolvedCorrectionProducer {
     // Prepare the type.
     var type = parameter.declaredFragment!.element.type;
     // TODO(scheglov): If the parameter is in a method declaration, and if the
-    // method overrides a method that has a type for the corresponding
-    // parameter, it would be nice to copy down the type from the overridden
-    // method.
+    //  method overrides a method that has a type for the corresponding
+    //  parameter, it would be nice to copy down the type from the overridden
+    //  method.
     if (type is! InterfaceType &&
-        //        type is! FunctionType &&
+        // type is! FunctionType &&
         type is! RecordType) {
       return;
     }
-    await _applyChange(builder, null, name, type);
+    var keyword = forRepresentationField
+        ? parameter.constFinalOrVarKeyword
+        : null;
+    await _applyChange(builder, keyword, name, type);
   }
 
   Future<void> _forVariableDeclaration(

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

@@ -738,7 +738,10 @@ final _builtInNonLintGenerators = <DiagnosticCode, List<ProducerGenerator>>{
     ConvertIntoBlockBody.missingBody,
   ],
   diag.recordLiteralOnePositionalNoTrailingCommaByType: [AddTrailingComma.new],
-  diag.representationFieldModifier: [RemoveKeyword.varKeyword],
+  diag.representationFieldModifier: [
+    AddTypeAnnotation.forRepresentationField,
+    RemoveKeyword.varKeyword,
+  ],
   diag.returnOfInvalidTypeFromClosure: [AddAsync.wrongReturnType],
   diag.returnOfInvalidTypeFromFunction: [
     AddAsync.wrongReturnType,

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

@@ -18,6 +18,7 @@ void main() {
     defineReflectiveTests(PreferTypingUninitializedVariablesBulkTest);
     defineReflectiveTests(PreferTypingUninitializedVariablesInFileTest);
     defineReflectiveTests(PreferTypingUninitializedVariablesLintTest);
+    defineReflectiveTests(RepresentationFieldModifierTest);
     defineReflectiveTests(SpecifyNonObviousLocalVariableTypesBulkTest);
     defineReflectiveTests(SpecifyNonObviousLocalVariableTypesInFileTest);
     defineReflectiveTests(SpecifyNonObviousLocalVariableTypesLintTest);
@@ -453,6 +454,21 @@ void f() {
   }
 }
 
+@reflectiveTest
+class RepresentationFieldModifierTest extends FixProcessorTest {
+  @override
+  FixKind get kind => DartFixKind.addTypeAnnotation;
+
+  Future<void> test_var() async {
+    await resolveTestCode('''
+extension type E(var v);
+''');
+    await assertHasFix('''
+extension type E(Object? v);
+''');
+  }
+}
+
 @reflectiveTest
 class SpecifyNonObviousLocalVariableTypesBulkTest extends BulkFixProcessorTest {
   @override

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

@@ -154,8 +154,12 @@ abstract class BulkFixProcessorTest extends AbstractSingleUnitTest {
     expect(resultCode, normalizeSource(expectedCode));
   }
 
-  Future<void> assertHasFix(String expected, {bool isParse = false}) async {
-    change = await _computeSourceChange(isParse: isParse);
+  Future<void> assertHasFix(
+    String expected, {
+    List<String>? codes,
+    bool isParse = false,
+  }) async {
+    change = await _computeSourceChange(codes: codes, isParse: isParse);
 
     // apply to "file"
     var fileEdits = change.edits;
@@ -184,11 +188,15 @@ abstract class BulkFixProcessorTest extends AbstractSingleUnitTest {
   }
 
   /// Computes fixes for the specified [testUnit].
-  Future<BulkFixProcessor> computeFixes({bool isParse = false}) async {
+  Future<BulkFixProcessor> computeFixes({
+    List<String>? codes,
+    bool isParse = false,
+  }) async {
     var analysisContext = contextFor(testFile);
     var processor = BulkFixProcessor(
       TestInstrumentationService(),
       await workspace,
+      codes: codes,
     );
     if (isParse) {
       await processor.fixErrorsUsingParsedResult([analysisContext]);
@@ -214,8 +222,11 @@ abstract class BulkFixProcessorTest extends AbstractSingleUnitTest {
   }
 
   /// Returns the source change for computed fixes in the specified [testUnit].
-  Future<SourceChange> _computeSourceChange({bool isParse = false}) async {
-    processor = await computeFixes(isParse: isParse);
+  Future<SourceChange> _computeSourceChange({
+    List<String>? codes,
+    bool isParse = false,
+  }) async {
+    processor = await computeFixes(codes: codes, isParse: isParse);
     return processor.builder.sourceChange;
   }