Better DDC sourcemap generation for lambdas

pkg/analyzer/lib/src/dart/ast/ast.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 analyzer.src.dart.ast.ast;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/syntactic_entity.dart';
@@ skipping 500 matching lines @@
   /**
    * Initialize a newly created as expression.
    */
   AsExpressionImpl(
       ExpressionImpl expression, this.asOperator, TypeAnnotationImpl type) {
     _expression = _becomeParentOf(expression);
     _type = _becomeParentOf(type);
   }
 
   @override
+  get length {

[Brian Wilkerson, 2017/04/11 19:07:51]

I think this is the wrong approach to fixing the problem, and that the synthetic
tokens are being created incorrectly and that that's what needs to be changed. A
synthetic token should have an offset that is equal to the end of the preceding
token and a length of zero. If you point me to the code that is creating these
tokens I'll be happy to take a look at it. (Making this change seems likely to
break server when dealing with invalid code that he parser has recovered from.)

[Alan Knight, 2017/04/11 20:32:06]

Per Jennifer, it doesn't seem like mapping these is even necessary, so I'll just
take this out of the CL.

These are being created in
pkg/dev_compiler/lib/src/compiler/reify_coercions.dart in the method
castExpression in CoercionReifier.

+    if (endToken.isSynthetic) {
+      return _expression.length;
+    } else {
+      return super.length;
+    }
+  }
+
+  @override
   Token get beginToken => _expression.beginToken;
 
   @override
   Iterable<SyntacticEntity> get childEntities =>
       new ChildEntities()..add(_expression)..add(asOperator)..add(_type);
 
   @override
   Token get endToken => _type.endToken;
 
   @override
@@ skipping 10954 matching lines @@
 
   @override
   dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
       visitor.visitYieldStatement(this);
 
   @override
   void visitChildren(AstVisitor visitor) {
     _expression?.accept(visitor);
   }
 }