Switch transformers over to source_span

pkg/code_transformers/lib/src/resolver.dart

 // Copyright (c) 2014, 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 code_transformer.src.resolver;
 
 import 'dart:async';
 
 import 'package:analyzer/src/generated/ast.dart' show Expression;
 import 'package:analyzer/src/generated/constant.dart' show EvaluationResult;
 import 'package:analyzer/src/generated/element.dart';
 import 'package:barback/barback.dart';
 import 'package:source_maps/refactor.dart';
-import 'package:source_maps/span.dart' show SourceFile, Span;
+import 'package:source_span/source_span.dart';
 
 
 /// Class for working with a barback based resolved AST.
 abstract class Resolver {
   /// Update the status of all the sources referenced by the entry points and
   /// update the resolved library. If [entryPoints] is omitted, the primary
   /// asset of [transform] is used as the only entry point.
   ///
   /// [release] must be called when done handling this Resolver to allow it
   /// to be used by later phases.
@@ skipping 54 matching lines @@
   ///
   /// Returns null if the library cannot be imported via an absolute URI or
   /// from [from] (if provided).
   Uri getImportUri(LibraryElement lib, {AssetId from});
 
   /// Get the asset ID of the file containing the asset.
   AssetId getSourceAssetId(Element element);
 
   /// Get the source span where the specified element was defined or null if
   /// the element came from the Dart SDK.
-  Span getSourceSpan(Element element);
+  SourceSpan getSourceSpan(Element element);
 
   /// Get a [SourceFile] with the contents of the file that defines [element],
   /// or null if the element came from the Dart SDK.
   SourceFile getSourceFile(Element element);
 
   /// Creates a text edit transaction for the given element if it is able
   /// to be edited, returns null otherwise.
   ///
   /// The transaction contains the entire text of the source file where the
   /// element originated. If the element was from a library part then the
   /// source file is the part file rather than the library.
   TextEditTransaction createTextEditTransaction(Element element);
 }