Fix summarization of closures in toplevel variable declarations in part files.

We were forgetting to include the unitNum, so it was defaulting to zero,
which worked for non-part files but not for part files.

R=scheglov@google.com

Review URL: https://codereview.chromium.org/2416863003 .

pkg/analyzer/lib/src/summary/link.dart

@@ -1216,14 +1216,19 @@ class CompilationUnitElementInBuildUnit extends CompilationUnitElementForLink {
           // TODO(paulberry): implement other cases as necessary
           throw new UnimplementedError('${element._unlinkedExecutable.kind}');
       }
-      return addRawReference(element.name,
+      if (enclosingClass == null) {
-          numTypeParameters: element.typeParameters.length,
+        return addRawReference(element.name,
-          containingReference:
+            numTypeParameters: element.typeParameters.length,
-              enclosingClass != null ? addReference(enclosingClass) : null,
+            dependency:
-          dependency: enclosingClass != null
+                library.addDependency(element.library as LibraryElementForLink),
-              ? null
+            unitNum: element.compilationUnit.unitNum,
-              : library.addDependency(element.library as LibraryElementForLink),
+            kind: kind);
-          kind: kind);
+      } else {
+        return addRawReference(element.name,
+            numTypeParameters: element.typeParameters.length,
+            containingReference: addReference(enclosingClass),
+            kind: kind);
+      }
     } else if (element is FunctionElementForLink_Initializer) {
       return addRawReference('',
           containingReference: addReference(element.enclosingElement),
@@ -1231,6 +1236,7 @@ class CompilationUnitElementInBuildUnit extends CompilationUnitElementForLink {
     } else if (element is TopLevelVariableElementForLink) {
       return addRawReference(element.name,
           dependency: library.addDependency(element.library),
+          unitNum: element.compilationUnit.unitNum,
           kind: ReferenceKind.topLevelPropertyAccessor);
     } else if (element is FieldElementForLink_ClassField) {
       ClassElementForLink_Class enclosingClass = element.enclosingElement;

pkg/analyzer/test/src/summary/resynthesize_common.dart

@@ -1635,6 +1635,14 @@ f() {
 ''');
   }
 
+  test_closure_in_variable_declaration_in_part() {
+    addSource('/a.dart', 'part of lib; final f = (int i) => i.toDouble();');
+    checkLibrary('''
+library lib;
+part "a.dart";
+''');
+  }
+
   test_const_invalid_field_const() {
     variablesWithNotConstInitializers.add('f');
     checkLibrary(