Stop concatenating prefixes and identifiers when performing lookup (issue 26069)

pkg/analyzer/lib/src/dart/ast/ast.dart

 // Copyright (c) 2014, 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.dart.ast.ast;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 8186 matching lines @@
 
   /**
    * Initialize a newly created prefixed identifier.
    */
   PrefixedIdentifierImpl(
       SimpleIdentifier prefix, this.period, SimpleIdentifier identifier) {
     _prefix = _becomeParentOf(prefix);
     _identifier = _becomeParentOf(identifier);
   }
 
+  /**
+   * Initialize a newly created prefixed identifier that does not take ownership
+   * of the components. The resulting node is only for temporary use, such as by
+   * resolution.
+   */
+  PrefixedIdentifierImpl.temp(this._prefix, this._identifier) : period = null;
+
   @override
   Token get beginToken => _prefix.beginToken;
 
   @override
   Element get bestElement {
     if (_identifier == null) {
       return null;
     }
     return _identifier.bestElement;
   }
@@ skipping 2755 matching lines @@
 
   @override
   dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
       visitor.visitYieldStatement(this);
 
   @override
   void visitChildren(AstVisitor visitor) {
     _expression?.accept(visitor);
   }
 }