First shot at source maps generation in dart2js.

lib/compiler/implementation/emitter.dart

Index: lib/compiler/implementation/emitter.dart
diff --git a/lib/compiler/implementation/emitter.dart b/lib/compiler/implementation/emitter.dart
index 3121e1fec87ce642397f0941394cb56826f79d59..9cd1a50fcea4deb5a43b9d21577859343019c6de 100644
--- a/lib/compiler/implementation/emitter.dart
+++ b/lib/compiler/implementation/emitter.dart
@@ -38,6 +38,7 @@ class CodeEmitterTask extends CompilerTask {
         boundClosureBuffer = new StringBuffer(),
         mainBuffer = new StringBuffer(),
         boundClosureCache = new Map<int, String>(),
+        sourceMappings = new List<SourceMappingEntry>(),
         super(compiler) {
     nativeEmitter = new NativeEmitter(this);
   }
@@ -597,7 +598,12 @@ function() {
     generatedCode.forEach((Element element, String codeBlock) {
       if (!element.isInstanceMember()) {
         String functionName = functionNamer(element);
-        buffer.add('$isolateProperties.$functionName = $codeBlock;\n\n');
+        buffer.add('$isolateProperties.$functionName = ');
+        int beginPosition = buffer.length;
+        buffer.add(codeBlock);
+        int endPosition = buffer.length;
+        buffer.add(';\n\n');
+        addSourceMapping(element, beginPosition, endPosition);
       }
     });
   }
@@ -1006,4 +1012,13 @@ if (typeof window != 'undefined' && typeof document != 'undefined' &&
     });
     return compiler.assembledCode;
   }
+
+  void addSourceMapping(FunctionElement element, int emittedBeginPosition, int emittedEndPosition) {

[podivilov, 2012/06/19 16:37:54]

This should probably be a method of SourceMapListener interface.

[ahe, 2012/06/19 17:00:41]

Long lines.

[podivilov, 2012/06/20 09:37:14]

Done.

+    SourceFile sourceFile = element.getCompilationUnit().script.file;
+    FunctionExpression expression = element.cachedNode;
+    sourceMappings.add(new SourceMappingEntry(sourceFile, expression.getBeginToken().charOffset, emittedBeginPosition));
+    sourceMappings.add(new SourceMappingEntry(sourceFile, expression.getEndToken().charOffset, emittedEndPosition));
+  }
+
+  final List<SourceMappingEntry> sourceMappings;
 }