Clear 'referenceMap' before summarizing a new unit.

pkg/analyzer/test/src/summary/summary_test.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 analyzer.test.src.summary.summary_test;
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_engine_io.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ skipping 1985 matching lines @@
         expectedTargetUnit: 1);
   }
 
   test_type_reference_to_nonexistent_file_via_prefix() {
     UnlinkedTypeRef typeRef = serializeTypeText('p.C',
         otherDeclarations: 'import "foo.dart" as p;', allowErrors: true);
     checkUnresolvedTypeRef(typeRef, 'p', 'C');
   }
 
   test_type_reference_to_part() {
-    addNamedSource('/a.dart', 'part of foo; class C {}');
-    checkTypeRef(
-        serializeTypeText('C',
-            otherDeclarations: 'library foo; part "a.dart";'),
-        null,
-        null,
-        'C',
+    addNamedSource('/a.dart', 'part of foo; class C { C(); }');
+    serializeLibraryText('library foo; part "a.dart"; C c;');
+    UnlinkedClass classA = findClass('C', unit: unlinkedUnits[1]);
+    checkTypeRef(classA.executables.single.returnType, null, null, 'C',
         expectedKind: PrelinkedReferenceKind.classOrEnum,
-        expectedTargetUnit: 1);
+        expectedTargetUnit: 1,
+        prelinkedSourceUnit: prelinked.units[1],
+        unlinkedSourceUnit: unlinkedUnits[1]);
   }
 
   test_type_reference_to_typedef() {
     checkTypeRef(serializeTypeText('F', otherDeclarations: 'typedef void F();'),
         null, null, 'F',
         expectedKind: PrelinkedReferenceKind.typedef);
   }
 
   test_type_unit_counts_unreferenced_units() {
     addNamedSource('/a.dart', 'library a; part "b.dart"; part "c.dart";');
@@ skipping 131 matching lines @@
         serializeClassText('class C { static int i; }').fields[0];
     expect(variable.isStatic, isTrue);
   }
 
   test_variable_type() {
     UnlinkedVariable variable =
         serializeVariableText('int i;', variableName: 'i');
     checkTypeRef(variable.type, 'dart:core', 'dart:core', 'int');
   }
 }