Better DDC sourcemap generation for lambdas

pkg/analyzer/lib/src/dart/ast/ast.dart

Index: pkg/analyzer/lib/src/dart/ast/ast.dart
diff --git a/pkg/analyzer/lib/src/dart/ast/ast.dart b/pkg/analyzer/lib/src/dart/ast/ast.dart
index 656b1c2edf45728f52417a3e76b25d498819e789..e6467df20dd6d881b5e41801f0419b6d1bb16b5a 100644
--- a/pkg/analyzer/lib/src/dart/ast/ast.dart
+++ b/pkg/analyzer/lib/src/dart/ast/ast.dart
@@ -518,6 +518,15 @@ class AsExpressionImpl extends ExpressionImpl implements AsExpression {
   }
 
   @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