Extension type. Report when the representation type is a bottom type.

See 3ecf3a729a

Change-Id: If58e262fb913a11edd8f0ecf3f2dcba6879ee65b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/331086
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

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

@@ -683,6 +683,8 @@ CompileTimeErrorCode.EXTENSION_TYPE_INHERITED_MEMBER_CONFLICT:
   status: noFix
 CompileTimeErrorCode.EXTENSION_TYPE_REPRESENTATION_DEPENDS_ON_ITSELF:
   status: noFix
+CompileTimeErrorCode.EXTENSION_TYPE_REPRESENTATION_TYPE_BOTTOM:
+  status: noFix
 CompileTimeErrorCode.EXTENSION_TYPE_WITH_ABSTRACT_MEMBER:
   status: needsFix
   notes: |-

pkg/analyzer/lib/src/error/codes.g.dart

@@ -1731,6 +1731,14 @@ class CompileTimeErrorCode extends AnalyzerErrorCode {
     correctionMessage: "Try specifying a different type.",
   );
 
+  ///  No parameters.
+  static const CompileTimeErrorCode EXTENSION_TYPE_REPRESENTATION_TYPE_BOTTOM =
+      CompileTimeErrorCode(
+    'EXTENSION_TYPE_REPRESENTATION_TYPE_BOTTOM',
+    "The representation type can't be a bottom type.",
+    correctionMessage: "Try specifying a different type.",
+  );
+
   ///  Parameters:
   ///  0: the name of the abstract method
   ///  1: the name of the enclosing extension type

pkg/analyzer/lib/src/error/error_code_values.g.dart

@@ -208,6 +208,7 @@ const List<ErrorCode> errorCodeValues = [
   CompileTimeErrorCode.EXTENSION_TYPE_IMPLEMENTS_REPRESENTATION_NOT_SUPERTYPE,
   CompileTimeErrorCode.EXTENSION_TYPE_INHERITED_MEMBER_CONFLICT,
   CompileTimeErrorCode.EXTENSION_TYPE_REPRESENTATION_DEPENDS_ON_ITSELF,
+  CompileTimeErrorCode.EXTENSION_TYPE_REPRESENTATION_TYPE_BOTTOM,
   CompileTimeErrorCode.EXTENSION_TYPE_WITH_ABSTRACT_MEMBER,
   CompileTimeErrorCode.EXTERNAL_FIELD_CONSTRUCTOR_INITIALIZER,
   CompileTimeErrorCode.EXTERNAL_FIELD_INITIALIZER,

pkg/analyzer/lib/src/generated/error_verifier.dart

@@ -714,6 +714,7 @@ class ErrorVerifier extends RecursiveAstVisitor<void>
       _checkForNonCovariantTypeParameterPositionInRepresentationType(
           node, element);
       _checkForExtensionTypeRepresentationDependsOnItself(node, element);
+      _checkForExtensionTypeRepresentationTypeBottom(node, element);
       _checkForExtensionTypeImplementsDeferred(node);
       _checkForExtensionTypeImplementsItself(node, element);
       _checkForExtensionTypeMemberConflicts(
@@ -2965,6 +2966,19 @@ class ErrorVerifier extends RecursiveAstVisitor<void>
     }
   }
 
+  void _checkForExtensionTypeRepresentationTypeBottom(
+    ExtensionTypeDeclarationImpl node,
+    ExtensionTypeElementImpl element,
+  ) {
+    final representationType = element.representation.type;
+    if (typeSystem.isBottom(representationType)) {
+      errorReporter.reportErrorForNode(
+        CompileTimeErrorCode.EXTENSION_TYPE_REPRESENTATION_TYPE_BOTTOM,
+        node.representation.fieldType,
+      );
+    }
+  }
+
   void _checkForExtensionTypeWithAbstractMember(
     ExtensionTypeDeclarationImpl node,
   ) {

pkg/analyzer/messages.yaml

@@ -5165,6 +5165,10 @@ CompileTimeErrorCode:
     problemMessage: "The extension type representation can't depend on itself."
     correctionMessage: Try specifying a different type.
     comment: No parameters.
+  EXTENSION_TYPE_REPRESENTATION_TYPE_BOTTOM:
+    problemMessage: "The representation type can't be a bottom type."
+    correctionMessage: Try specifying a different type.
+    comment: No parameters.
   EXTENSION_TYPE_WITH_ABSTRACT_MEMBER:
     problemMessage: "'{0}' must have a method body because '{1}' is an extension type."
     correctionMessage: "Try adding a body to '{0}'."

pkg/analyzer/test/src/diagnostics/conflicting_generic_interfaces_test.dart

@@ -224,6 +224,8 @@ class B implements I<num> {}
 extension type C(Never it) implements A, B {}
 ''', [
       error(CompileTimeErrorCode.CONFLICTING_GENERIC_INTERFACES, 87, 1),
+      error(CompileTimeErrorCode.EXTENSION_TYPE_REPRESENTATION_TYPE_BOTTOM, 89,
+          5),
     ]);
   }
 

pkg/analyzer/test/src/diagnostics/extension_type_representation_type_bottom_test.dart

@@ -0,0 +1,27 @@
+// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analyzer/src/error/codes.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import '../dart/resolution/context_collection_resolution.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(ExtensionTypeRepresentationTypeBottomTest);
+  });
+}
+
+@reflectiveTest
+class ExtensionTypeRepresentationTypeBottomTest
+    extends PubPackageResolutionTest {
+  test_never() async {
+    await assertErrorsInCode('''
+extension type A(Never it) {}
+''', [
+      error(CompileTimeErrorCode.EXTENSION_TYPE_REPRESENTATION_TYPE_BOTTOM, 17,
+          5),
+    ]);
+  }
+}

pkg/analyzer/test/src/diagnostics/test_all.dart

@@ -277,6 +277,8 @@ import 'extension_type_inherited_member_conflict_test.dart'
     as extension_type_inherited_member_conflict;
 import 'extension_type_representation_depends_on_itself_test.dart'
     as extension_type_representation_depends_on_itself;
+import 'extension_type_representation_type_bottom_test.dart'
+    as extension_type_representation_type_bottom;
 import 'extension_type_with_abstract_member_test.dart'
     as extension_type_with_abstract_member;
 import 'external_field_constructor_initializer_test.dart'
@@ -1097,6 +1099,7 @@ main() {
     extension_type_implements_representation_not_supertype.main();
     extension_type_inherited_member_conflict.main();
     extension_type_representation_depends_on_itself.main();
+    extension_type_representation_type_bottom.main();
     extension_type_with_abstract_member.main();
     external_field_constructor_initializer.main();
     external_field_initializer.main();

tests/language/extension_type/extension_type_representation_type_test.dart

@@ -15,6 +15,8 @@ import "dart:async" show FutureOr;
 extension type V01(dynamic _) {}
 extension type V02(void _) {}
 extension type V03(Never _) {}
+//                 ^^^^^
+// [analyzer] COMPILE_TIME_ERROR.EXTENSION_TYPE_REPRESENTATION_TYPE_BOTTOM
 extension type V04(Null _) {}
 extension type V05(Function _) {}
 extension type V06(Record _) {}