Move a number of packages and some of pub over to using source_span.

pkg/string_scanner/lib/src/string_scanner.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 string_scanner.string_scanner;
 
-import 'package:source_maps/source_maps.dart';
+import 'package:source_span/source_span.dart';
 
 import 'exception.dart';
 import 'utils.dart';
 
 /// When compiled to JS, forward slashes are always escaped in [RegExp.pattern].
 ///
 /// See issue 17998.
 final _slashAutoEscape = new RegExp("/").pattern == "\\/";
 
 /// A class that scans through a string using [Pattern]s.
@@ skipping 27 matching lines @@
   /// The portion of the string that hasn't yet been scanned.
   String get rest => string.substring(position);
 
   /// Whether the scanner has completely consumed [string].
   bool get isDone => position == string.length;
 
   /// Creates a new [StringScanner] that starts scanning from [position].
   ///
   /// [position] defaults to 0, the beginning of the string. [sourceUrl] is the
   /// URL of the source of the string being scanned, if available. It can be
-  /// either a [String] or a [Uri].
+  /// a [String], a [Uri], or `null`.
   StringScanner(this.string, {sourceUrl, int position})
       : sourceUrl = sourceUrl is String ? Uri.parse(sourceUrl) : sourceUrl {
     if (position != null) this.position = position;
   }
 
   /// Consumes a single character and returns its character code.
   ///
   /// This throws a [FormatException] if the string has been fully consumed. It
   /// doesn't affect [lastMatch].
   int readChar() {
@@ skipping 80 matching lines @@
   /// It's an error to pass [match] at the same time as [position] or [length].
   void error(String message, {Match match, int position, int length}) {
     validateErrorArgs(string, match, position, length);
 
     if (match == null && position == null && length == null) match = lastMatch;
     if (position == null) {
       position = match == null ? this.position : match.start;
     }
     if (length == null) length = match == null ? 1 : match.end - match.start;
 
-    var url = sourceUrl == null ? null : sourceUrl.toString();
-    var sourceFile = new SourceFile.text(url, string);
+    var sourceFile = new SourceFile(string, url: sourceUrl);
     var span = sourceFile.span(position, position + length);
-    throw new StringScannerException(message, string, sourceUrl, span);
+    throw new StringScannerException(message, span, string);
   }
 
   // TODO(nweiz): Make this handle long lines more gracefully.
   /// Throws a [FormatException] describing that [name] is expected at the
   /// current position in the string.
   void _fail(String name) {
     error("expected $name.", position: this.position, length: 0);
   }
 }