The parameter of synthetic setters should inherit 'covariant'.

pkg/analyzer/test/src/summary/summary_common.dart

 // Copyright (c) 2015, 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.
 
 library analyzer.test.src.summary.summary_common;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/src/dart/scanner/reader.dart';
@@ skipping 7699 matching lines @@
   }
 
   test_field() {
     UnlinkedClass cls = serializeClassText('class C { int i; }');
     UnlinkedVariable variable = findVariable('i', variables: cls.fields);
     expect(variable, isNotNull);
     expect(variable.isConst, isFalse);
     expect(variable.isStatic, isFalse);
     expect(variable.isFinal, isFalse);
     expect(variable.initializer, isNull);
+    expect(variable.inheritsCovariantSlot, isNot(0));
     expect(findExecutable('i', executables: cls.executables), isNull);
     expect(findExecutable('i=', executables: cls.executables), isNull);
     expect(unlinkedUnits[0].publicNamespace.names, hasLength(1));
     expect(unlinkedUnits[0].publicNamespace.names[0].name, 'C');
     expect(unlinkedUnits[0].publicNamespace.names[0].members, isEmpty);
   }
 
   test_field_const() {
     UnlinkedVariable variable =
         serializeClassText('class C { static const int i = 0; }').fields[0];
     expect(variable.isConst, isTrue);
+    expect(variable.inheritsCovariantSlot, 0);
     assertUnlinkedConst(variable.initializer.bodyExpr,
         operators: [UnlinkedExprOperation.pushInt], ints: [0]);
   }
 
   test_field_documented() {
     if (!includeInformative) return;
     String text = '''
 class C {
   /**
    * Docs
    */
   var v;
 }''';
     UnlinkedVariable variable = serializeClassText(text).fields[0];
     expect(variable.documentationComment, isNotNull);
     checkDocumentationComment(variable.documentationComment, text);
   }
 
   test_field_final() {
     UnlinkedVariable variable =
         serializeClassText('class C { final int i = 0; }').fields[0];
     expect(variable.isFinal, isTrue);
+    expect(variable.inheritsCovariantSlot, 0);
     assertUnlinkedConst(variable.initializer.bodyExpr,
         operators: [UnlinkedExprOperation.pushInt], ints: [0]);
   }
 
   test_field_final_notConstExpr() {
     UnlinkedVariable variable = serializeClassText(r'''
 class C {
   final int f = 1 + m();
   static int m() => 42;
 }''').fields[0];
@@ skipping 101 matching lines @@
     UnlinkedVariable v =
         serializeClassText('class C { static var v; }').fields[0];
     expect(v.inferredTypeSlot, 0);
   }
 
   test_field_static() {
     UnlinkedVariable variable =
         serializeClassText('class C { static int i; }').fields[0];
     expect(variable.isStatic, isTrue);
     expect(variable.initializer, isNull);
+    expect(variable.inheritsCovariantSlot, 0);
     expect(unlinkedUnits[0].publicNamespace.names, hasLength(1));
     expect(unlinkedUnits[0].publicNamespace.names[0].name, 'C');
     expect(unlinkedUnits[0].publicNamespace.names[0].members, hasLength(1));
     expect(unlinkedUnits[0].publicNamespace.names[0].members[0].name, 'i');
     expect(unlinkedUnits[0].publicNamespace.names[0].members[0].kind,
         ReferenceKind.propertyAccessor);
     expect(
         unlinkedUnits[0].publicNamespace.names[0].members[0].numTypeParameters,
         0);
     expect(
         unlinkedUnits[0].publicNamespace.names[0].members[0].members, isEmpty);
   }
 
   test_field_static_final() {
     UnlinkedVariable variable =
         serializeClassText('class C { static final int i = 0; }').fields[0];
     expect(variable.isStatic, isTrue);
     expect(variable.isFinal, isTrue);
     expect(variable.initializer.bodyExpr, isNull);
+    expect(variable.inheritsCovariantSlot, 0);
   }
 
   test_field_static_final_untyped() {
     UnlinkedVariable variable =
         serializeClassText('class C { static final x = 0; }').fields[0];
     expect(variable.initializer.bodyExpr, isNotNull);
+    expect(variable.inheritsCovariantSlot, 0);
   }
 
   test_field_untyped() {
     UnlinkedVariable variable =
         serializeClassText('class C { var x = 0; }').fields[0];
     expect(variable.initializer.bodyExpr, isNotNull);
+    expect(variable.inheritsCovariantSlot, isNot(0));
   }
 
   test_fully_linked_references_follow_other_references() {
     if (!strongMode || skipFullyLinkedData) {
       return;
     }
     serializeLibraryText('final x = 0; String y;');
     checkLinkedTypeSlot(
         unlinkedUnits[0].variables[0].inferredTypeSlot, 'dart:core', 'int');
     checkTypeRef(unlinkedUnits[0].variables[1].type, 'dart:core', 'String');
@@ skipping 2693 matching lines @@
  */
 class _PrefixExpectation {
   final ReferenceKind kind;
   final String name;
   final String absoluteUri;
   final int numTypeParameters;
 
   _PrefixExpectation(this.kind, this.name,
       {this.absoluteUri, this.numTypeParameters: 0});
 }