re-land fix #27110 with proper DDC side of changes

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

Index: pkg/analyzer/lib/src/task/strong/ast_properties.dart
diff --git a/pkg/analyzer/lib/src/task/strong/ast_properties.dart b/pkg/analyzer/lib/src/task/strong/ast_properties.dart
index 52f27f1cef073a1a4c08ca0044870dd352dad34a..0f93adafca085809e4b0c8e0414bb1eabc547188 100644
--- a/pkg/analyzer/lib/src/task/strong/ast_properties.dart
+++ b/pkg/analyzer/lib/src/task/strong/ast_properties.dart
@@ -10,6 +10,7 @@
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/element/type.dart';
 
+const String _implicitAssignmentCast = '_implicitAssignmentCast';
 const String _implicitCast = '_implicitCast';
 const String _hasImplicitCasts = '_hasImplicitCasts';
 const String _isDynamicInvoke = '_isDynamicInvoke';
@@ -37,6 +38,17 @@ void setImplicitCast(Expression node, DartType type) {
   node.setProperty(_implicitCast, type);
 }
 
+/// 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);
+}
+
+/// Sets the result of [getImplicitAssignmentCast] for this node.
+void setImplicitAssignmentCast(Expression node, DartType type) {
+  node.setProperty(_implicitAssignmentCast, type);
+}
+
 /// True if this node is a dynamic operation that requires dispatch and/or
 /// checking at runtime.
 bool isDynamicInvoke(Expression node) {