Fix referencing prefixed types from parts.

pkg/analyzer/lib/src/summary/summarize_elements.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 serialization.elements;
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/type.dart';
 import 'package:analyzer/src/generated/resolver.dart';
@@ skipping 656 matching lines @@
         b.reference = referenceMap.putIfAbsent(element, () {
           assert(unlinkedReferences.length == prelinkedReferences.length);
           CompilationUnitElement unitElement =
               element.getAncestor((Element e) => e is CompilationUnitElement);
           int unit = dependentLibrary.units.indexOf(unitElement);
           assert(unit != -1);
           int numTypeParameters = 0;
           if (element is TypeParameterizedElement) {
             numTypeParameters = element.typeParameters.length;
           }
-          int index = unlinkedReferences.length;
           // Figure out a prefix that may be used to refer to the given type.
           // TODO(paulberry): to avoid subtle relinking inconsistencies we
           // should use the actual prefix from the AST (a given type may be
           // reachable via multiple prefixes), but sadly, this information is
           // not recorded in the element model.
           int prefixReference = 0;
           PrefixElement prefix = prefixMap[element];
           if (prefix != null) {
             prefixReference = serializePrefix(prefix);
           }
+          int index = unlinkedReferences.length;
           unlinkedReferences.add(encodeUnlinkedReference(
               name: element.name, prefixReference: prefixReference));
           prelinkedReferences.add(encodePrelinkedReference(
               dependency: serializeDependency(dependentLibrary),
               kind: element is FunctionTypeAliasElement
                   ? PrelinkedReferenceKind.typedef
                   : PrelinkedReferenceKind.classOrEnum,
               unit: unit,
               numTypeParameters: numTypeParameters));
           return index;
@@ skipping 46 matching lines @@
     b.nameOffset = variable.nameOffset;
     b.type = serializeTypeRef(variable.type, variable);
     b.isStatic = variable.isStatic && variable.enclosingElement is ClassElement;
     b.isFinal = variable.isFinal;
     b.isConst = variable.isConst;
     b.hasImplicitType = variable.hasImplicitType;
     b.documentationComment = serializeDocumentation(variable);
     return b;
   }
 }