First shot at source maps generation in dart2js.

lib/compiler/implementation/compiler.dart

 // Copyright (c) 2012, 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.
 
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
 final bool REPORT_EXCESS_RESOLUTION = false;
@@ skipping 43 matching lines @@
 class JavaScriptBackend extends Backend {
   SsaBuilderTask builder;
   SsaOptimizerTask optimizer;
   SsaCodeGeneratorTask generator;
   CodeEmitterTask emitter;
 
   List<CompilerTask> get tasks() {
     return <CompilerTask>[builder, optimizer, generator, emitter];
   }
 
-  JavaScriptBackend(Compiler compiler)
-      : emitter = new CodeEmitterTask(compiler),
+  JavaScriptBackend(Compiler compiler, [bool generateSourceMap = false])

[ahe, 2012/06/20 11:56:59]

Prefer no optional arguments to a method (or constructor in this case) that is
basically used once.

[podivilov, 2012/06/20 14:15:15]

Done.

+      : emitter = new CodeEmitterTask(compiler, generateSourceMap),
         super(compiler) {
     builder = new SsaBuilderTask(this);
     optimizer = new SsaOptimizerTask(this);
     generator = new SsaCodeGeneratorTask(this);
   }
 
   void enqueueHelpers(Enqueuer world) {
     enqueueAllTopLevelFunctions(compiler.jsHelperLibrary, world);
     enqueueAllTopLevelFunctions(compiler.interceptorsLibrary, world);
     for (var helper in [const SourceString('Closure'),
@@ skipping 109 matching lines @@
   static final int PHASE_SCANNING = 0;
   static final int PHASE_RESOLVING = 1;
   static final int PHASE_COMPILING = 2;
   static final int PHASE_RECOMPILING = 3;
   int phase;
 
   Compiler([this.tracer = const Tracer(),
             this.enableTypeAssertions = false,
             this.enableUserAssertions = false,
             bool emitJavascript = true,
-            validateUnparse = false])
+            validateUnparse = false,
+            generateSourceMap = false])

[ahe, 2012/06/20 11:56:59]

I think the default should be true.

[podivilov, 2012/06/20 14:15:15]

Done.

       : libraries = new Map<String, LibraryElement>(),
         world = new World(),
         progress = new Stopwatch.start() {
     namer = new Namer(this);
     constantHandler = new ConstantHandler(this);
     scanner = new ScannerTask(this);
     dietParser = new DietParserTask(this);
     parser = new ParserTask(this);
     validator = new TreeValidatorTask(this);
     unparseValidator = new UnparseValidator(this, validateUnparse);
     resolver = new ResolverTask(this);
     checker = new TypeCheckerTask(this);
     backend = emitJavascript ?
-        new JavaScriptBackend(this) : new dart_backend.DartBackend(this);
+        new JavaScriptBackend(this, generateSourceMap) :
+        new dart_backend.DartBackend(this);
     enqueuer = new EnqueueTask(this);
     tasks = [scanner, dietParser, parser, resolver, checker,
              unparseValidator, constantHandler, enqueuer];
     tasks.addAll(backend.tasks);
   }
 
   Universe get resolverWorld() => enqueuer.resolution.universe;
   Universe get codegenWorld() => enqueuer.codegen.universe;
 
   int getNextFreeClassId() => nextFreeClassId++;
@@ skipping 544 matching lines @@
     // invariant that endOffset > beginOffset, but for EOF the
     // charoffset of the next token may be [beginOffset]. This can
     // also happen for synthetized tokens that are produced during
     // error handling.
     final endOffset =
       Math.max((end.next !== null) ? end.next.charOffset : 0, beginOffset + 1);
     assert(endOffset > beginOffset);
     return f(beginOffset, endOffset);
   }
 }