Add a fix when an extension or mixin has a primary constructor

Neither is allowed to have a primary constructor, This adds a fix to
remove the primary constructor.

Closes https://github.com/dart-lang/sdk/issues/63073

Change-Id: I363d2fa02d18e2a63a2bfc8c64a57256f861195d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/500584
Reviewed-by: Keerti Parthasarathy <keertip@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

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

@@ -26,6 +26,15 @@ class RemoveConstructor extends ResolvedCorrectionProducer {
   Future<void> compute(ChangeBuilder builder) async {
     var container = _findContainer();
     if (container == null) {
+      // If there's no container, then it must be a primary constructor.
+      var primary = _findPrimaryConstructor();
+      if (primary != null) {
+        await builder.addDartFileEdit(file, (builder) {
+          builder.addDeletion(
+            range.startEnd(primary.leftParen, primary.rightParen),
+          );
+        });
+      }
       return;
     }
 
@@ -83,6 +92,40 @@ class RemoveConstructor extends ResolvedCorrectionProducer {
     }
     return null;
   }
+
+  _PrimaryConstructor? _findPrimaryConstructor() {
+    switch (node) {
+      case ExtensionDeclaration extension:
+        var leftParen =
+            extension.typeParameters?.endToken.next ?? extension.name?.next;
+        var rightParen = extension.onClause?.onKeyword.previous;
+        if (leftParen != null &&
+            leftParen.type == TokenType.OPEN_PAREN &&
+            rightParen != null &&
+            rightParen.type == TokenType.CLOSE_PAREN) {
+          return _PrimaryConstructor(
+            leftParen: leftParen,
+            rightParen: rightParen,
+          );
+        }
+      case MixinDeclaration mixin:
+        var leftParen = mixin.typeParameters?.endToken.next ?? mixin.name.next;
+        var rightParen =
+            mixin.onClause?.onKeyword.previous ??
+            mixin.implementsClause?.implementsKeyword.previous ??
+            mixin.body.beginToken.previous;
+        if (leftParen != null &&
+            leftParen.type == TokenType.OPEN_PAREN &&
+            rightParen != null &&
+            rightParen.type == TokenType.CLOSE_PAREN) {
+          return _PrimaryConstructor(
+            leftParen: leftParen,
+            rightParen: rightParen,
+          );
+        }
+    }
+    return null;
+  }
 }
 
 class _Container {
@@ -91,3 +134,10 @@ class _Container {
 
   _Container({required this.leftBracket, required this.members});
 }
+
+class _PrimaryConstructor {
+  final Token leftParen;
+  final Token rightParen;
+
+  _PrimaryConstructor({required this.leftParen, required this.rightParen});
+}

pkg/analysis_server/lib/src/services/correction/error_fix_status.yaml

@@ -715,7 +715,7 @@ extension_override_with_cascade:
 extension_override_without_access:
   status: noFix
 extension_primary_constructor:
-  status: needsEvaluation
+  status: hasFix
 extension_type_constructor_with_super_formal_parameter:
   status: needsFix
   notes: |-
@@ -1141,7 +1141,7 @@ mixin_of_type_alias_expands_to_type_parameter:
 mixin_on_type_alias_expands_to_type_parameter:
   status: noFix
 mixin_primary_constructor:
-  status: needsEvaluation
+  status: hasFix
 mixin_subtype_of_base_is_not_base:
   status: hasFix
 mixin_subtype_of_final_is_not_base:

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

@@ -572,6 +572,7 @@ final _builtInNonLintGenerators = <DiagnosticCode, List<ProducerGenerator>>{
   diag.extensionTypeDeclaresInstanceField: [ConvertIntoGetter.new],
   diag.extensionOverrideAccessToStaticMember: [ReplaceWithExtensionName.new],
   diag.extensionOverrideWithCascade: [ReplaceCascadeWithDot.new],
+  diag.extensionPrimaryConstructor: [RemoveConstructor.new],
   diag.extensionTypeWithAbstractMember: [ConvertIntoBlockBody.missingBody],
   diag.extraPositionalArguments: [CreateConstructor.new],
   diag.extraPositionalArgumentsCouldBeNamed: [
@@ -659,6 +660,7 @@ final _builtInNonLintGenerators = <DiagnosticCode, List<ProducerGenerator>>{
   diag.missingRequiredArgument: [AddMissingRequiredArgument.new],
   diag.mixinApplicationNotImplementedInterface: [ExtendClassForMixin.new],
   diag.mixinClassDeclarationExtendsNotObject: [RemoveExtendsClause.new],
+  diag.mixinPrimaryConstructor: [RemoveConstructor.new],
   diag.mixinSubtypeOfBaseIsNotBase: [AddClassModifier.baseModifier],
   diag.mixinSubtypeOfFinalIsNotBase: [AddClassModifier.baseModifier],
   diag.mixinOfDisallowedClass: [RemoveNameFromDeclarationClause.new],

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

@@ -103,6 +103,24 @@ extension E on int {
     await assertHasFix('''
 extension E on int {
 }
+''');
+  }
+
+  Future<void> test_primaryConstructor() async {
+    await resolveTestCode('''
+extension E() on int;
+''');
+    await assertHasFix('''
+extension E on int;
+''');
+  }
+
+  Future<void> test_primaryConstructor_withTypeParameters() async {
+    await resolveTestCode('''
+extension E<T>() on int;
+''');
+    await assertHasFix('''
+extension E<T> on int;
 ''');
   }
 }
@@ -195,6 +213,51 @@ mixin M {
     await assertHasFix('''
 mixin M {
 }
+''');
+  }
+
+  Future<void> test_primaryConstructor_emptyBody() async {
+    await resolveTestCode('''
+mixin M() {}
+''');
+    await assertHasFix('''
+mixin M {}
+''');
+  }
+
+  Future<void> test_primaryConstructor_implements() async {
+    await resolveTestCode('''
+mixin M() implements Object {}
+''');
+    await assertHasFix('''
+mixin M implements Object {}
+''');
+  }
+
+  Future<void> test_primaryConstructor_semicolon() async {
+    await resolveTestCode('''
+mixin M();
+''');
+    await assertHasFix('''
+mixin M;
+''');
+  }
+
+  Future<void> test_primaryConstructor_withOnClause() async {
+    await resolveTestCode('''
+mixin M() on Object {}
+''');
+    await assertHasFix('''
+mixin M on Object {}
+''');
+  }
+
+  Future<void> test_primaryConstructor_withTypeParameters() async {
+    await resolveTestCode('''
+mixin M<T>() {}
+''');
+    await assertHasFix('''
+mixin M<T> {}
 ''');
   }
 }