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

pkg/analyzer/lib/src/fasta/ast_builder.dart

Index: pkg/analyzer/lib/src/fasta/ast_builder.dart
diff --git a/pkg/analyzer/lib/src/fasta/ast_builder.dart b/pkg/analyzer/lib/src/fasta/ast_builder.dart
index 8baab7cbe24322f052c5fe9e8a7ebca8114b13fd..0a37fa0bab12e468b46f67f3be770320200105c8 100644
--- a/pkg/analyzer/lib/src/fasta/ast_builder.dart
+++ b/pkg/analyzer/lib/src/fasta/ast_builder.dart
@@ -35,6 +35,7 @@ import 'element_store.dart'
         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 {
@@ -292,7 +293,8 @@ class AstBuilder extends ScopeListener {
     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) {