Use declared return type for inference of return and yield statements.

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

Index: pkg/front_end/lib/src/fasta/kernel/body_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index 42d3a59efa81f35d779ece3d562a0f71cce3c456..6a7bece2662e6ff4aebc8bf3d5203c08f06fd902 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -480,12 +480,11 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   }
 
   @override
-  void finishFunction(
-      FormalParameters formals, AsyncMarker asyncModifier, Statement body) {
+  void finishFunction(FunctionNode function, FormalParameters formals,
+      AsyncMarker asyncModifier, Statement body) {

[ahe, 2017/05/24 16:00:21]

You can access FunctionNode like this:

member.target.function

This way, you can probably avoid most of the changes in this CL?

[Paul Berry, 2017/05/24 16:20:16]

Yes, that worked!  Thank you, that makes this CL much less invasive.

     debugEvent("finishFunction");
     typePromoter.finished();
-    // TODO(paulberry): get function return type from the outline.
-    _typeInferrer.inferFunctionBody(null, asyncModifier, body);
+    _typeInferrer.inferFunctionBody(function.returnType, asyncModifier, body);
     KernelFunctionBuilder builder = member;
     builder.body = body;
     if (formals?.optional != null) {