Handle clash of prefix/non-prefix imports.

sdk/lib/_internal/compiler/implementation/library_loader.dart

 // Copyright (c) 2012, 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.
 
 part of dart2js;
 
 /**
  * [CompilerTask] for loading libraries and setting up the import/export scopes.
  *
  * The library loader uses four different kinds of URIs in different parts of
@@ skipping 503 matching lines @@
   /**
    * Imports the library into the [importingLibrary].
    */
   void importLibrary(Compiler compiler, LibraryElement importingLibrary) {
     assert(invariant(importingLibrary,
                      importedLibrary.exportsHandled,
                      message: 'Exports not handled on $importedLibrary'));
     var combinatorFilter = new CombinatorFilter.fromTag(import);
     if (import != null && import.prefix != null) {
       SourceString prefix = import.prefix.source;
-      Element e = importingLibrary.find(prefix);
-      if (e == null) {
-        e = new PrefixElementX(prefix, importingLibrary.entryCompilationUnit,
-                               import.getBeginToken());
-        importingLibrary.addToScope(e, compiler);
+      Element existingElement = importingLibrary.find(prefix);
+      PrefixElement prefixElement;
+      if (existingElement == null || !existingElement.isPrefix()) {
+        prefixElement = new PrefixElementX(prefix,
+            importingLibrary.entryCompilationUnit, import.getBeginToken());
+      } else {
+        prefixElement = existingElement;
       }
-      if (!identical(e.kind, ElementKind.PREFIX)) {
-        compiler.withCurrentElement(e, () {
-          compiler.reportWarning(e, 'duplicated definition');
-        });
-        compiler.reportFatalError(
-            import.prefix,
-            MessageKind.GENERIC, {'text': 'Error: Duplicate definition.'});
-      }
-      PrefixElement prefixElement = e;
+      importingLibrary.addToScope(prefixElement, compiler);
       importedLibrary.forEachExport((Element element) {
         if (combinatorFilter.exclude(element)) return;
-        // TODO(johnniwinther): Clean-up like [checkDuplicateLibraryName].
-        Element existing =
-            prefixElement.imported.putIfAbsent(element.name, () => element);
-        if (!identical(existing, element)) {
-          compiler.withCurrentElement(existing, () {
-            compiler.reportWarning(existing, 'duplicated import');
-          });
-          compiler.withCurrentElement(element, () {
-            compiler.reportFatalError(
-                element,
-                MessageKind.GENERIC, {'text': 'Error: Duplicated import.'});
-          });
-        }
+        prefixElement.addImport(element, import, compiler);
       });
     } else {
       importedLibrary.forEachExport((Element element) {
         compiler.withCurrentElement(importingLibrary, () {
           if (combinatorFilter.exclude(element)) return;
           importingLibrary.addImport(element, import, compiler);
         });
       });
     }
   }
@@ skipping 352 matching lines @@
   }
 
   /**
    * Registers all top-level entities of [library] as starting point for the
    * fixed-point computation of the import/export scopes.
    */
   void registerLibraryExports(LibraryElement library) {
     nodeMap[library].registerInitialExports();
   }
 }