fix #27259, implement covariance checking for strong mode and DDC

pkg/analyzer/lib/src/task/strong/ast_properties.dart

 // Copyright (c) 2016, 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.
 
 /// Properties that result from Strong Mode analysis on an AST.
 ///
 /// These properties are not public, but provided by use of back-ends such as
 /// Dart Dev Compiler.
 import 'package:analyzer/analyzer.dart';
+import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 
 const String _hasImplicitCasts = '_hasImplicitCasts';
-const String _implicitAssignmentCast = '_implicitAssignmentCast';
+const String _implicitOperationCast = '_implicitAssignmentCast';
 const String _implicitCast = '_implicitCast';
 const String _isDynamicInvoke = '_isDynamicInvoke';
+const String _classCovariantParameters = '_classCovariantParameters';
+const String _superclassCovariantParameters = '_superclassCovariantParameters';
+const String _covariantGenericReturn = '_covariantGenericReturn';
+const String _covariantPrivateFields = '_covariantPrivateFields';
+const String _covariantPrivateMembers = '_covariantPrivateMembers';
 
-/// If this op-assign has an implicit cast on the assignment, returns the type
-/// it is coerced to, otherwise returns null.
-DartType getImplicitAssignmentCast(Expression node) {
-  return node.getProperty/*<DartType>*/(_implicitAssignmentCast);
+/// If this expression needs an implicit cast on a subexpression that cannot be
+/// expressed anywhere else, returns the type it is coerced to.
+///
+/// For example, op-assign can have an implicit cast on the final assignment,
+/// and MethodInvocation calls on functions (`obj.f()` where `obj.f` is an
+/// accessor and not a real method) can need a cast on the function.
+DartType getImplicitOperationCast(Expression node) {
+  return node.getProperty/*<DartType>*/(_implicitOperationCast);
 }
 
 /// If this expression has an implicit cast, returns the type it is coerced to,
 /// otherwise returns null.
 DartType getImplicitCast(Expression node) {
   return node.getProperty/*<DartType>*/(_implicitCast);
 }
 
 /// True if this compilation unit has any implicit casts, otherwise false.
 ///
 /// See also [getImplicitCast].
 bool hasImplicitCasts(CompilationUnit node) {
   return node.getProperty/*<bool>*/(_hasImplicitCasts) ?? false;
 }
 
 /// True if this node is a dynamic operation that requires dispatch and/or
 /// checking at runtime.
 bool isDynamicInvoke(Expression node) {
   return node.getProperty/*<bool>*/(_isDynamicInvoke) ?? false;
 }
 
 /// Sets [hasImplicitCasts] property for this compilation unit.
 void setHasImplicitCasts(CompilationUnit node, bool value) {
   node.setProperty(_hasImplicitCasts, value == true ? true : null);
 }
 
-/// Sets the result of [getImplicitAssignmentCast] for this node.
-void setImplicitAssignmentCast(Expression node, DartType type) {
-  node.setProperty(_implicitAssignmentCast, type);
+/// Sets the result of [getImplicitOperationCast] for this node.
+void setImplicitOperationCast(Expression node, DartType type) {
+  node.setProperty(_implicitOperationCast, type);
 }
 
 /// Sets the result of [getImplicitCast] for this node.
 void setImplicitCast(Expression node, DartType type) {
   node.setProperty(_implicitCast, type);
 }
 
-/// Sets [isDynamicInvoke] property for this expression
+/// Sets [isDynamicInvoke] property for this expression.
 void setIsDynamicInvoke(Expression node, bool value) {
   node.setProperty(_isDynamicInvoke, value == true ? true : null);
 }
+
+/// Returns a list of parameters and method type parameters in this class
+/// declaration that need a check at runtime to ensure soundness.
+Set<Element> getClassCovariantParameters(Declaration node) {
+  return node.getProperty(_classCovariantParameters);
+}
+
+/// Sets [getClassCovariantParameters] property for this class.
+void setClassCovariantParameters(Declaration node, Set<Element> value) {
+  node.setProperty(_classCovariantParameters, value);
+}
+
+/// Returns a list of parameters and method type parameters from mixins and
+/// superclasses of this class that need a stub method to check their type at
+/// runtime for soundness.
+Set<Element> getSuperclassCovariantParameters(Declaration node) {
+  return node.getProperty(_superclassCovariantParameters);
+}
+
+/// Sets [getSuperclassCovariantParameters] property for this class.
+void setSuperclassCovariantParameters(Declaration node, Set<Element> value) {
+  node.setProperty(_superclassCovariantParameters, value);
+}
+
+/// Gets the private setters and methods that are accessed unsafely from
+/// this compilation unit.
+///
+/// These members will require a check.
+Set<ExecutableElement> getCovariantPrivateMembers(CompilationUnit node) {
+  return node.getProperty(_covariantPrivateMembers);
+}
+
+/// Sets [getCovariantPrivateMembers] property for this compilation unit.
+void setCovariantPrivateMembers(
+    CompilationUnit node, Set<ExecutableElement> value) {
+  node.setProperty(_covariantPrivateMembers, value);
+}