Infer AsExpression types.

pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
index 48a7845160516d20b6cb907503d7d3b92afba579..63fb3f22cc4e46ae0068b96b877895caaa7ddedd 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
@@ -30,8 +30,7 @@ class KernelAsExpression extends AsExpression implements KernelExpression {
   @override
   DartType _inferExpression(
       KernelTypeInferrer inferrer, DartType typeContext, bool typeNeeded) {
-    // TODO(scheglov): implement.
-    return typeNeeded ? const DynamicType() : null;
+    return typeNeeded ? type : null;

[Paul Berry, 2017/05/04 17:05:18]

You need to recurse into the subexpression in case it contains anything that
needs to be inferred or promoted.  So this method body should be:

inferrer.inferAsExpression(typeContext, typeNeeded, operand, type);

And TypeInferrerImpl.inferAsExpression should look something like this:

DartType inferAsExpression(...) {
  inferExpression(operand, null, false);
  return typeNeeded ? type : null;
}

[scheglov, 2017/05/04 17:27:32]

Ah, yes.
Of course.

   }
 }