Cache PrefixElement(s) in LibraryElementImpl.

pkg/analyzer/lib/src/dart/element/element.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.element.element;
 
 import 'dart:collection';
 import 'dart:math' show min;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 3732 matching lines @@
       if (_unlinkedImport.isImplicit) {
         return -1;
       }
       return _unlinkedImport.offset;
     }
     return super.nameOffset;
   }
 
   PrefixElement get prefix {
     if (_unlinkedImport != null) {
-      if (_unlinkedImport.prefixReference != 0) {
+      if (_unlinkedImport.prefixReference != 0 && _prefix == null) {
         LibraryElementImpl library = enclosingElement as LibraryElementImpl;
         _prefix = new PrefixElementImpl.forSerialized(_unlinkedImport, library);
       }
     }
     return _prefix;
   }
 
   void set prefix(PrefixElement prefix) {
     assert(_unlinkedImport == null);
     _prefix = prefix;
@@ skipping 205 matching lines @@
    */
   Namespace _exportNamespace;
 
   /**
    * The public [Namespace] of this library, `null` if it has not been
    * computed yet.
    */
   Namespace _publicNamespace;
 
   /**
+   * The cached list of prefixes.
+   */
+  List<PrefixElement> _prefixes;
+
+  /**
    * Initialize a newly created library element in the given [context] to have
    * the given [name] and [offset].
    */
   LibraryElementImpl(this.context, String name, int offset, this.nameLength)
       : resynthesizerContext = null,
         _unlinkedDefiningUnit = null,
         super(name, offset);
 
   /**
    * Initialize a newly created library element in the given [context] to have
@@ skipping 162 matching lines @@
    * given list of [imports].
    */
   void set imports(List<ImportElement> imports) {
     for (ImportElement importElement in imports) {
       (importElement as ImportElementImpl).enclosingElement = this;
       PrefixElementImpl prefix = importElement.prefix as PrefixElementImpl;
       if (prefix != null) {
         prefix.enclosingElement = this;
       }
     }
     this._imports = imports;

[Brian Wilkerson, 2016/05/21 15:22:05]

We should flush _prefixes here.

[scheglov, 2016/05/22 01:53:38]

Done.

   }
 
   @override
   bool get isBrowserApplication =>
       entryPoint != null && isOrImportsBrowserLibrary;
 
   @override
   bool get isDartAsync => name == "dart.async";
 
   @override
@@ skipping 152 matching lines @@
     for (CompilationUnitElement compilationUnit in parts) {
       assert((compilationUnit as CompilationUnitElementImpl).librarySource ==
           source);
       (compilationUnit as CompilationUnitElementImpl).enclosingElement = this;
     }
     this._parts = parts;
   }
 
   @override
   List<PrefixElement> get prefixes {
-    HashSet<PrefixElement> prefixes = new HashSet<PrefixElement>();
-    for (ImportElement element in _imports) {
-      PrefixElement prefix = element.prefix;
-      if (prefix != null) {
-        prefixes.add(prefix);
+    if (_prefixes == null) {
+      HashSet<PrefixElement> prefixes = new HashSet<PrefixElement>();
+      for (ImportElement element in _imports) {
+        PrefixElement prefix = element.prefix;
+        if (prefix != null) {
+          prefixes.add(prefix);
+        }
       }
+      _prefixes = prefixes.toList();
     }
-    return new List.from(prefixes);
+    return _prefixes;
   }
 
   @override
   Namespace get publicNamespace {
     if (resynthesizerContext != null) {
       _publicNamespace ??= resynthesizerContext.buildPublicNamespace();
     }
     return _publicNamespace;
   }
 
@@ skipping 2195 matching lines @@
 
   @override
   void visitElement(Element element) {
     int offset = element.nameOffset;
     if (offset != -1) {
       map[offset] = element;
     }
     super.visitElement(element);
   }
 }