Report CompileTimeErrorCode.DUPLICATE_PART when not only URI, but even Source is the same.

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 1492 matching lines @@
       CompilationUnit partUnit = partUnits[i];
       Source partSource = partUnit.element.source;
       partUnitMap[partSource] = partUnit;
     }
     //
     // Update "part" directives.
     //
     LibraryIdentifier libraryNameNode = null;
     String partsLibraryName = _UNKNOWN_LIBRARY_NAME;
     bool hasPartDirective = false;
-    Set<String> seenPartUris = new Set<String>();
+    Set<Source> seenPartSources = new Set<Source>();
     FunctionElement entryPoint =
         _findEntryPoint(definingCompilationUnitElement);
     List<Directive> directivesToResolve = <Directive>[];
     List<CompilationUnitElementImpl> sourcedCompilationUnits =
         <CompilationUnitElementImpl>[];
     NodeList<Directive> directives = definingCompilationUnit.directives;
     int directiveLength = directives.length;
     for (int i = 0; i < directiveLength; i++) {
       Directive directive = directives[i];
       if (directive is LibraryDirective) {
         libraryNameNode = directive.name;
         directivesToResolve.add(directive);
       } else if (directive is PartDirective) {
         StringLiteral partUri = directive.uri;
         Source partSource = directive.uriSource;
         hasPartDirective = true;
         CompilationUnit partUnit = partUnitMap[partSource];
         if (partUnit != null) {
           CompilationUnitElementImpl partElement = partUnit.element;
           partElement.uriOffset = partUri.offset;
           partElement.uriEnd = partUri.end;
           partElement.uri = directive.uriContent;
           //
-          // Validate that the part URI is unique in the library.
+          // Validate that the part source is unique in the library.
           //
-          if (!seenPartUris.add(directive.uriContent)) {
+          if (!seenPartSources.add(partSource)) {
             errors.add(new AnalysisError(
                 librarySource,
                 partUri.offset,
                 partUri.length,
                 CompileTimeErrorCode.DUPLICATE_PART,
                 [directive.uriContent]));

[Brian Wilkerson, 2016/10/06 22:14:11]

We should either restore the argument to the message (my preference) or remove
it here.

           }
           //
           // Validate that the part contains a part-of directive with the same
           // name as the library.
           //
           if (context.exists(partSource)) {
             String partLibraryName =
                 _getPartLibraryName(partSource, partUnit, directivesToResolve);
             if (partLibraryName == null) {
               errors.add(new AnalysisError(
@@ skipping 4888 matching lines @@
 
   @override
   bool moveNext() {
     if (_newSources.isEmpty) {
       return false;
     }
     currentTarget = _newSources.removeLast();
     return true;
   }
 }