anchor.diff:    return uri;
   }
   
  -/// Adjusts the source paths in [sourceMap] to be relative paths,and returns
  +/// Adjusts the source uris in [sourceMap] to be relative uris, and returns
   /// the new map.
  -///
  -/// Relative paths are in terms of URIs ('/'), not local OS paths (e.g.,
  -/// windows '\').
   ///
   /// Source uris show up in two forms, absolute `file:` uris and custom
   /// [multiRootScheme] uris (also "absolute" uris, but always relative to some
  
positive.code:         // `/packages` path, we do that by stripping the `/lib` prefix and
          // relying on the `multiRootOutputPath` to be set to the proper
          // packages dir (so /packages/<package>).
          if (shortPath.startsWith('/lib')) {
            assert(multiRootOutputPath.startsWith('/packages'));
            shortPath = shortPath.substring(4);
          }
          var multiRootPath = "${multiRootOutputPath ?? ''}$shortPath";
  
negative.code: ///   to the [multiRootOutputPath], and assert that [multiRootOutputPath]
  ///   starts with `/packages` (more explanation inline).
  ///
  // TODO(#40251): Remove this logic from dev_compiler itself, push it to the
  // invokers of dev_compiler which have more knowledge about how they want
  // source paths to look.
  Map placeSourceMap(Map sourceMap, String sourceMapPath, String multiRootScheme,
      {String multiRootOutputPath, String sourceMapBase}) {
    var map = Map.from(sourceMap);
  