Handle 'part of' declarations with URI correctly in Fasta.

pkg/front_end/lib/src/fasta/source/outline_builder.dart

 // Copyright (c) 2016, 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 fasta.outline_builder;
 
 import 'package:kernel/ast.dart' show AsyncMarker, ProcedureKind;
 
 import '../parser/parser.dart' show FormalParameterType, optional;
 
@@ skipping 558 matching lines @@
 
   @override
   void endTypeVariable(Token token, Token extendsOrSuper) {
     debugEvent("endTypeVariable");
     TypeBuilder bound = pop();
     String name = pop();
     push(library.addTypeVariable(name, bound, token.charOffset));
   }
 
   @override
-  void endPartOf(Token partKeyword, Token semicolon) {
+  void endPartOf(Token partKeyword, Token semicolon, bool hasName) {
     debugEvent("endPartOf");
-    String name = pop();
+    String name = hasName ? pop() : null;

[Paul Berry, 2017/03/14 14:48:23]

I see what you're doing here, but IMHO it's a little hard to follow.  Consider
doing this instead:

String containingLib = pop();
List<MetadataBuilder> metadata = pop();
if (hasName) {
  library.addPartOf(metadata, containingLib, null);
} else {
  library.addPartOf(metadata, null, containingLib);
}

[ahe, 2017/03/15 14:05:36]

Honestly, I wasn't super happy with it either :-)

+    String uri = hasName ? null : pop();
     List<MetadataBuilder> metadata = pop();
-    library.addPartOf(metadata, name);
+    library.addPartOf(metadata, name, uri);
   }
 
   @override
   void endConstructorReference(
       Token start, Token periodBeforeName, Token endToken) {
     debugEvent("ConstructorReference");
     String suffix = popIfNotNull(periodBeforeName);
     List<TypeBuilder> typeArguments = pop();
     String name = pop();
     push(library.addConstructorReference(
@@ skipping 106 matching lines @@
   Link<Token> handleMemberName(Link<Token> identifiers) {
     if (!isDartLibrary || identifiers.isEmpty) return identifiers;
     return removeNativeClause(identifiers);
   }
 
   @override
   void debugEvent(String name) {
     // printEvent(name);
   }
 }