Don't attempt to record reference to a named parameter of a synthetic function.

pkg/analyzer/test/src/dart/analysis/index_test.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.
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
@@ skipping 796 matching lines @@
     await _indexTestUnit('''
 foo({var p}) {}
 main() {
   foo(p: 1);
 }
 ''');
     Element element = findElement('p');
     assertThat(element)..isReferencedAt('p: 1', true);
   }
 
+  test_isReferencedBy_synthetic_leastUpperBound() async {
+    await _indexTestUnit('''
+int f1({int p}) => 1;
+int f2({int p}) => 2;
+main(bool b) {
+  var f = b ? f1 : f2;
+  f(p: 0);
+}''');
+    // We should not crash because of reference to "p" - a named parameter
+    // of a synthetic LUB FunctionElement created for "f".
+  }
+
   test_isReferencedBy_TopLevelVariableElement() async {
     provider.newFile(
         _p('$testProject/lib.dart'),
         '''
 library lib;
 var V;
 ''');
     await _indexTestUnit('''
 import 'lib.dart' show V; // imp
 import 'lib.dart' as pref;
@@ skipping 404 matching lines @@
   final bool isQualified;
 
   _Relation(this.kind, this.offset, this.length, this.isQualified);
 
   @override
   String toString() {
     return '_Relation{kind: $kind, offset: $offset, length: $length, '
         'isQualified: $isQualified}lified)';
   }
 }