Test fix for bad typing

Author: kevmoo

pubspec.yaml

@@ -1,5 +1,5 @@
 name: source_gen
-version: 0.5.0+1
+version: 0.5.1-dev
 author: Dart Team <[email protected]>
 description: Automatic sourcecode generation for Dart
 homepage: https://github.com/dart-lang/source_gen

test/json_serializable_test.dart

@@ -115,17 +115,12 @@ void main() {
 const _generator = const JsonSerializableGenerator();
 
 Future<Element> _getClassForCodeString(String name) async {
-  var elements = await _getElementsForCodeString();
-
-  return elements.singleWhere((e) => e.name == name);
-}
-
-Future<List<Element>> _getElementsForCodeString() async {
   if (_compUnit == null) {
     _compUnit = await _getCompilationUnitForString(getPackagePath());
   }
 
-  return getElementsFromLibraryElement(_compUnit.element.library);
+  return getElementsFromLibraryElement(_compUnit.element.library)
+      .singleWhere((e) => e.name == name);
 }
 
 Future<CompilationUnit> _getCompilationUnitForString(String projectPath) async {