Fix strong-mode warnings.

lib/parser.dart

 // Copyright (c) 2013, 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.
 
 /// Contains the top-level function to parse source maps version 3.
 library source_maps.parser;
 
 import 'dart:collection';
 import 'dart:convert';
 
@@ skipping 164 matching lines @@
 
     // Indices associated with file urls that will be part of the source map. We
     // use a linked hash-map so that `_urls.keys[_urls[u]] == u`
     var urls = new LinkedHashMap<String, int>();
 
     // Indices associated with identifiers that will be part of the source map.
     // We use a linked hash-map so that `_names.keys[_names[n]] == n`
     var names = new LinkedHashMap<String, int>();
 
     var lineNum;
-    var targetEntries;
+    List<TargetEntry> targetEntries;
     for (var sourceEntry in sourceEntries) {
       if (lineNum == null || sourceEntry.target.line > lineNum) {
         lineNum = sourceEntry.target.line;
         targetEntries = <TargetEntry>[];
         lines.add(new TargetLineEntry(lineNum, targetEntries));
       }
 
       if (sourceEntry.source == null) {
         targetEntries.add(new TargetEntry(sourceEntry.target.column));
       } else {
         var sourceUrl = sourceEntry.source.sourceUrl;
         var urlId = urls.putIfAbsent(
             sourceUrl == null ? '' : sourceUrl.toString(), () => urls.length);
         var srcNameId = sourceEntry.identifierName == null ? null :
             names.putIfAbsent(sourceEntry.identifierName, () => names.length);
         targetEntries.add(new TargetEntry(
             sourceEntry.target.column,
             urlId,
             sourceEntry.source.line,
             sourceEntry.source.column,
             srcNameId));
       }
     }
     return new SingleMapping._(
         fileUrl, urls.keys.toList(), names.keys.toList(), lines);
   }
 
   SingleMapping.fromJson(Map map, {mapUrl})
       : targetUrl = map['file'],
-        urls = map['sources'],
-        names = map['names'],
+        urls = map['sources'] as List<String>,

[Siggi Cherem (dart-lang), 2016/03/24 01:15:02]

+leafp - would this cause a runtime check failure?

Json decoders allocate generic lists and maps with dynamic type arguments (since
we don't know what the List contains until you parse the contents).

[Leaf, 2016/03/24 03:23:41]

Yep.  If map['sources'] returns something with reified type List<dynamic>, this
cast will fail in ddc.  If copying the list doesn't matter (that is, you're not
relying on mutations to the original list showing up in your new list), then you
can do a new List<String>.from(...) here.  Otherwise... it gets a bit tricky. 
I'm starting to wonder whether we should write delegating wrappers for common
types like this that do type checks on reads.  That doesn't handle any identity
issues, but it at least allows sharing the underlying mutable state.

[nweiz, 2016/03/24 19:07:54]

Good catch, done.

@leafp: That would also be nice for just avoiding the overhead of copying. I've
filed https://github.com/dart-lang/collection/issues/25 to track it.

[Siggi Cherem (dart-lang), 2016/03/24 19:36:19]

+1 - it would be good to avoid coping.

+        names = map['names'] as List<String>,
         sourceRoot = map['sourceRoot'],
         lines = <TargetLineEntry>[],
         _mapUrl = mapUrl is String ? Uri.parse(mapUrl) : mapUrl {
     int line = 0;
     int column = 0;
     int srcUrlId = 0;
     int srcLine = 0;
     int srcColumn = 0;
     int srcNameId = 0;
     var tokenizer = new _MappingTokenizer(map['mappings']);
@@ skipping 295 matching lines @@
   static const _TokenKind EOF = const _TokenKind(isEof: true);
   static const _TokenKind VALUE = const _TokenKind();
   final bool isNewLine;
   final bool isNewSegment;
   final bool isEof;
   bool get isValue => !isNewLine && !isNewSegment && !isEof;
 
   const _TokenKind(
       {this.isNewLine: false, this.isNewSegment: false, this.isEof: false});
 }