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

pkg/front_end/lib/src/fasta/source/stack_listener.dart

Index: pkg/front_end/lib/src/fasta/source/stack_listener.dart
diff --git a/pkg/front_end/lib/src/fasta/source/stack_listener.dart b/pkg/front_end/lib/src/fasta/source/stack_listener.dart
index c133b207ab13676aa3108f8596bc63df7bffbfff..7a2f9189bac922f8e7e26d5040a911105adb593d 100644
--- a/pkg/front_end/lib/src/fasta/source/stack_listener.dart
+++ b/pkg/front_end/lib/src/fasta/source/stack_listener.dart
@@ -12,7 +12,7 @@ import '../parser/identifier_context.dart' show IdentifierContext;
 
 import '../scanner.dart' show BeginGroupToken, Token;
 
-import 'package:kernel/ast.dart' show AsyncMarker;
+import 'package:kernel/ast.dart' show AsyncMarker, FunctionNode;
 
 import '../errors.dart' show inputError, internalError;
 
@@ -60,8 +60,8 @@ abstract class StackListener extends Listener {
 
   // TODO(ahe): This doesn't belong here. Only implemented by body_builder.dart
   // and ast_builder.dart.
-  void finishFunction(
-      covariant formals, AsyncMarker asyncModifier, covariant body) {
+  void finishFunction(FunctionNode function, covariant formals,
+      AsyncMarker asyncModifier, covariant body) {
     return internalError("Unsupported operation");
   }