Elements. Migrate CreateFile.

Change-Id: Ia12f6d090b9895e48998da1f589eb55126e2f16c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/391541
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Keerti Parthasarathy <[email protected]>

Author: scheglov

pkg/analysis_server/analyzer_use_new_elements.txt

@@ -314,6 +314,7 @@ lib/src/services/correction/dart/create_class.dart
 lib/src/services/correction/dart/create_constructor.dart
 lib/src/services/correction/dart/create_constructor_for_final_fields.dart
 lib/src/services/correction/dart/create_field.dart
+lib/src/services/correction/dart/create_file.dart
 lib/src/services/correction/dart/create_function.dart
 lib/src/services/correction/dart/create_getter.dart
 lib/src/services/correction/dart/create_local_variable.dart

pkg/analysis_server/lib/src/services/correction/dart/create_file.dart

@@ -51,8 +51,9 @@ class CreateFile extends ResolvedCorrectionProducer {
         if (source != null) {
           var pathContext = resourceProvider.pathContext;
           var relativePath = pathContext.relative(
-              unitResult.libraryElement.source.fullName,
-              from: pathContext.dirname(source.fullName));
+            unitResult.libraryElement2.firstFragment.source.fullName,
+            from: pathContext.dirname(source.fullName),
+          );
 
           // URIs always use forward slashes regardless of platform.
           var relativeUri = pathContext.split(relativePath).join('/');