Validate native tags

sdk/lib/_internal/compiler/implementation/native_handler.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.
 
 library native;
 
 import 'dart:collection' show Queue;
 import 'dart2jslib.dart';
 import 'dart_types.dart';
 import 'elements/elements.dart';
@@ skipping 519 matching lines @@
         if (name.contains('Error')) return true;
         return false;
       },
       'native exception');
   }
 }
 
 
 class NativeResolutionEnqueuer extends NativeEnqueuerBase {
 
+  Map<String, ClassElement> tagOwner = new Map<String, ClassElement>();
+
   NativeResolutionEnqueuer(Enqueuer world, Compiler compiler)
     : super(world, compiler, compiler.enableNativeLiveTypeAnalysis);
 
+  void processNativeClass(ClassElement classElement) {
+    super.processNativeClass(classElement);
+
+    // Since we map from dispatch tags to classes, a dispatch tag must be used
+    // on only one native class.
+    for (String tag in nativeTagsOfClass(classElement)) {
+      ClassElement owner = tagOwner[tag];
+      if (owner != null) {
+        compiler.reportError(classElement,
+            MessageKind.GENERIC,
+            {'text': "Tag '$tag' already in use by '${owner.name}'"});
+      } else {
+        tagOwner[tag] = classElement;
+      }
+    }
+  }
+
   void logSummary(log(message)) {
     log('Resolved ${registeredClasses.length} native elements used, '
         '${unusedClasses.length} native elements dead.');
   }
 }
 
 
 class NativeCodegenEnqueuer extends NativeEnqueuerBase {
 
   final CodeEmitterTask emitter;
@@ skipping 488 matching lines @@
   Node node = listener.nodes.head;
   if (node != null
       && node.asIdentifier() != null
       && node.asIdentifier().source == 'native') {
     nativeTagInfo = node.asIdentifier().token.next.value;
     listener.popNode();
   }
   return nativeTagInfo;
 }
 
+// The tags string contains comma-separated 'words' which are either dispatch
+// tags (having JavaScript identifier syntax) and directives that begin with
+// `!`.
+List<String> nativeTagsOfClassRaw(ClassElement cls) {
+  String quotedName = cls.nativeTagInfo;
+  return quotedName.substring(1, quotedName.length - 1).split(',');
+}
+
+List<String> nativeTagsOfClass(ClassElement cls) {
+  return nativeTagsOfClassRaw(cls).where((s) => !s.startsWith('!')).toList();
+}
+
+bool nativeTagsForcedNonLeaf(ClassElement cls) =>
+    nativeTagsOfClassRaw(cls).contains('!nonleaf');
+
+
 final RegExp nativeRedirectionRegExp = new RegExp(r'^[a-zA-Z][a-zA-Z_$0-9]*$');
 
 void handleSsaNative(SsaBuilder builder, Expression nativeBody) {
   Compiler compiler = builder.compiler;
   FunctionElement element = builder.work.element;
   NativeEmitter nativeEmitter = builder.nativeEmitter;
   JavaScriptBackend backend = builder.backend;
 
   HInstruction convertDartClosure(Element parameter, FunctionType type) {
     HInstruction local = builder.localsHandler.readLocal(parameter);
@@ skipping 77 matching lines @@
     }
     LiteralString jsCode = nativeBody.asLiteralString();
     builder.push(new HForeign.statement(
         new js.LiteralStatement(jsCode.dartString.slowToString()),
         <HInstruction>[],
         new SideEffects(),
         null,
         backend.dynamicType));
   }
 }