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

pkg/dev_compiler/lib/src/compiler/reify_coercions.dart

Index: pkg/dev_compiler/lib/src/compiler/reify_coercions.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/reify_coercions.dart b/pkg/dev_compiler/lib/src/compiler/reify_coercions.dart
index 595d540c30cb8ebf13f2485d91236cd8f93369ea..77b40eb05eebee79c4131bc8d71894f8bb9d8e1e 100644
--- a/pkg/dev_compiler/lib/src/compiler/reify_coercions.dart
+++ b/pkg/dev_compiler/lib/src/compiler/reify_coercions.dart
@@ -132,9 +132,17 @@ class _TreeCloner extends analyzer.AstCloner {
     if (clone is Expression) {
       ast_properties.setImplicitCast(
           clone, ast_properties.getImplicitCast(node));
+      ast_properties.setImplicitOperationCast(
+          clone, ast_properties.getImplicitOperationCast(node));
       ast_properties.setIsDynamicInvoke(
           clone, ast_properties.isDynamicInvoke(node));
     }
+    if (clone is ClassDeclaration) {
+      ast_properties.setClassCovariantParameters(
+          clone, ast_properties.getClassCovariantParameters(node));
+      ast_properties.setSuperclassCovariantParameters(
+          clone, ast_properties.getSuperclassCovariantParameters(node));
+    }
   }
 
   @override