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

pkg/analyzer/lib/src/fasta/ast_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.analyzer.ast_builder;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast_factory.dart' show AstFactory;
 import 'package:analyzer/dart/ast/standard_ast_factory.dart' as standard;
 import 'package:analyzer/dart/ast/token.dart' as analyzer show Token;
@@ skipping 17 matching lines @@
 import 'package:front_end/src/fasta/source/scope_listener.dart'
     show JumpTargetKind, NullValue, ScopeListener;
 import 'analyzer.dart' show toKernel;
 import 'element_store.dart'
     show
         AnalyzerLocalVariableElemment,
         AnalyzerParameterElement,
         ElementStore,
         KernelClassElement;
 import 'package:analyzer/src/dart/error/syntactic_errors.dart';
+import 'package:kernel/ast.dart' show FunctionNode;
 import 'token_utils.dart' show toAnalyzerToken, toAnalyzerCommentToken;
 
 class AstBuilder extends ScopeListener {
   final AstFactory ast = standard.astFactory;
 
   final ErrorReporter errorReporter;
   final KernelLibraryBuilder library;
   final Builder member;
   final ElementStore elementStore;
 
@@ skipping 237 matching lines @@
     if (beginToken != null) {
       exitLocalScope();
     }
     Block block = ast.block(
         toAnalyzerToken(beginToken), statements, toAnalyzerToken(endToken));
     analyzer.Token star = pop();
     analyzer.Token asyncKeyword = pop();
     push(ast.blockFunctionBody(asyncKeyword, star, block));
   }
 
-  void finishFunction(formals, asyncModifier, FunctionBody body) {
+  void finishFunction(
+      FunctionNode function, formals, asyncModifier, FunctionBody body) {
     debugEvent("finishFunction");
     Statement bodyStatement;
     if (body is EmptyFunctionBody) {
       bodyStatement = ast.emptyStatement(body.semicolon);
     } else if (body is ExpressionFunctionBody) {
       bodyStatement = ast.returnStatement(null, body.expression, null);
     } else {
       bodyStatement = (body as BlockFunctionBody).block;
     }
     var kernel = toKernel(bodyStatement, elementStore, library.library, scope);
@@ skipping 1794 matching lines @@
       } else if (identical('var', s)) {
         finalConstOrVarKeyword = token;
       } else if (identical('covariant', s)) {
         covariantKeyword = token;
       } else {
         internalError('Unhandled modifier: $s');
       }
     }
   }
 }