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

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

 // Copyright (c) 2016, 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 fasta.body_builder;
 
 import '../fasta_codes.dart'
     show FastaMessage, codeExpectedButGot, codeExpectedFunctionBody;
 
 import '../parser/parser.dart' show FormalParameterType, MemberKind, optional;
@@ skipping 462 matching lines @@
   void handleNoInitializers() {
     debugEvent("NoInitializers");
   }
 
   @override
   void endInitializers(int count, Token beginToken, Token endToken) {
     debugEvent("Initializers");
   }
 
   @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) {
       Iterator<FormalParameterBuilder> formalBuilders =
           builder.formals.skip(formals.required.length).iterator;
       for (VariableDeclaration parameter in formals.optional.formals) {
         bool hasMore = formalBuilders.moveNext();
         assert(hasMore);
         VariableDeclaration realParameter = formalBuilders.current.target;
         Expression initializer =
@@ skipping 2689 matching lines @@
     if (starToken == null) {
       return AsyncMarker.Async;
     } else {
       assert(identical(starToken.stringValue, "*"));
       return AsyncMarker.AsyncStar;
     }
   } else {
     return internalError("Unknown async modifier: $asyncToken");
   }
 }