Invalidate resolution if a unit instantiate a class with the unnamed constructor change.

pkg/analyzer/lib/src/task/dart.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.src.task.dart;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 2588 matching lines @@
   }
 
   bool hasAffectedReferences(ReferencedNames references, Source refLibrary) {
     // Resolution must be performed when a referenced element changes.
     for (String name in references.names) {
       if (isChangedOrClassMember(refLibrary, name)) {
         _log(() => '$refLibrary is affected by $name');
         return true;
       }
     }
+    // Resolution must be performed when the unnamed constructor of
+    // an instantiated class is added/changed/removed.
+    // TODO(scheglov) Use only instantiations with default constructor.
+    for (String name in references.instantiatedNames) {
+      for (ClassElementDelta classDelta in changedClasses.values) {
+        if (classDelta.name == name && classDelta.hasUnnamedConstructorChange) {
+          _log(() =>
+              '$refLibrary is affected by the default constructor of $name');
+          return true;
+        }
+      }
+    }
     return false;
   }
 
   /**
    * Return `true` if the given [name], used in a unit of the [librarySource],
    * is affected by a changed top-level element, excluding classes.
    */
   bool isChanged(Source librarySource, String name) {
     if (_isPrivateName(name)) {
       if (changedPrivateNames[librarySource]?.contains(name) ?? false) {
@@ skipping 3852 matching lines @@
 
   @override
   bool moveNext() {
     if (_newSources.isEmpty) {
       return false;
     }
     currentTarget = _newSources.removeLast();
     return true;
   }
 }