Store actual Reference(s) for additional exports.

pkg/front_end/lib/src/fasta/source/source_library_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.source_library_builder;
 
-import 'package:kernel/ast.dart' show ProcedureKind;
+import 'package:kernel/ast.dart' show ProcedureKind, Reference;
 
 import '../../base/resolve_relative_uri.dart' show resolveRelativeUri;
 
 import '../../scanner/token.dart' show Token;
 
 import '../builder/builder.dart'
     show
         Builder,
         ClassBuilder,
         ConstructorReferenceBuilder,
         FormalParameterBuilder,
         FunctionTypeBuilder,
-        InvalidTypeBuilder,
         LibraryBuilder,
         MemberBuilder,
         MetadataBuilder,
         NamedTypeBuilder,
         PrefixBuilder,
         ProcedureBuilder,
         Scope,
         TypeBuilder,
         TypeDeclarationBuilder,
         TypeVariableBuilder,
@@ skipping 16 matching lines @@
         templateMissingPartOf,
         templatePartOfLibraryNameMismatch,
         templatePartOfUriMismatch,
         templatePartOfUseUri,
         templatePartTwice;
 
 import '../import.dart' show Import;
 
 import '../problems.dart' show unhandled;
 
-import '../util/relativize.dart' show relativizeUri;
-
 import 'source_loader.dart' show SourceLoader;
 
 abstract class SourceLibraryBuilder<T extends TypeBuilder, R>
     extends LibraryBuilder<T, R> {
   final SourceLoader loader;
 
   final DeclarationBuilder<T> libraryDeclaration;
 
   final List<ConstructorReferenceBuilder> constructorReferences =
       <ConstructorReferenceBuilder>[];
@@ skipping 23 matching lines @@
   List<MetadataBuilder> metadata;
 
   /// The current declaration that is being built. When we start parsing a
   /// declaration (class, method, and so on), we don't have enough information
   /// to create a builder and this object records its members and types until,
   /// for example, [addClass] is called.
   DeclarationBuilder<T> currentDeclaration;
 
   bool canAddImplementationBuilders = false;
 
-  /// Exports in addition to the members declared in this library.
-  ///
-  /// See [../dill/dill_library_builder.dart] for additional details on the
-  /// format used.
-  List<List<String>> additionalExports;
+  /// References to nodes exported by the `export` directives, don't conflict
+  /// with each other, and not are hidden by local declarations.
+  List<Reference> additionalExports;
 
   SourceLibraryBuilder(SourceLoader loader, Uri fileUri)
       : this.fromScopes(loader, fileUri, new DeclarationBuilder<T>.library(),
             new Scope.top());
 
   SourceLibraryBuilder.fromScopes(
       this.loader, this.fileUri, this.libraryDeclaration, this.importScope)
       : disableTypeInference = loader.target.disableTypeInference,
         currentDeclaration = libraryDeclaration,
         super(
@@ skipping 399 matching lines @@
       }
       import.finalizeImports(this);
     }
     if (!explicitCoreImport) {
       loader.coreLibrary.exportScope.forEach((String name, Builder member) {
         addToScope(name, member, -1, true);
       });
     }
     exportScope.forEach((String name, Builder member) {
       if (member.parent != this) {
-        additionalExports ??= <List<String>>[];
+        additionalExports ??= <Reference>[];
         Builder parent = member.parent;
         if (parent is LibraryBuilder) {
-          additionalExports.add(<String>[
-            relativizeUri(parent.uri, base: uri.resolve(".")),
-            name
-          ]);
-        } else {
-          InvalidTypeBuilder invalidType = member;
-          String message = invalidType.message.message;
-          additionalExports.add(<String>[null, name, message]);
+          additionalExports.add(member.target.reference);

[scheglov, 2017/08/29 16:56:57]

The specification says that it is an error to re-export two different nodes with
the same name.

18.2 Exports
It is a compile-time error if a name N is re-exported by a library L and N is
introduced into the export namespace of L by more than one export, unless all
exports refer to same declaration for the name N.

I would say that with presence of a compile-time error we are free to do
whatever reasonable thing we decide to do. In this case we should report an
error in L, and skip N from its export namespace.

[ahe, 2017/08/30 14:24:52]

I had more time to think about this. I think it is important for error recovery
that we can serialize errors regarding ambiguous imports and exports. Yes, the
specification doesn't require the behavior of the Dart VM here, but I do think
it is important that we can represent errors at all positions in the kernel AST.

If we agree on the general principle, I don't mind deferring the implementation
of that (possibly leaving it to the kernel team to work out precisely how to
handle these kinds of errors).

         }
       }
     });
   }
 
   @override
   void addToScope(String name, Builder member, int charOffset, bool isImport) {
     Map<String, Builder> map =
         member.isSetter ? importScope.setters : importScope.local;
     Builder existing = map[name];
@@ skipping 135 matching lines @@
   /// synthesize type variables on the factory matching the class'.
   void addFactoryDeclaration(
       ProcedureBuilder procedure, DeclarationBuilder<T> factoryDeclaration) {
     factoryDeclarations[procedure] = factoryDeclaration;
   }
 
   Scope toScope(Scope parent) {
     return new Scope(members, setters, parent, isModifiable: false);
   }
 }