ErrorResult::handler fix

pkgs/async/lib/src/result/error.dart

@@ -47,10 +47,15 @@ class ErrorResult implements Result<Never> {
   /// has to be a function expecting only one argument, which will be called
   /// with only the error.
   void handle(Function errorHandler) {
-    if (errorHandler is ZoneBinaryCallback) {
+    if (errorHandler is dynamic Function(Object, StackTrace)) {
       errorHandler(error, stackTrace);
+    } else if (errorHandler is dynamic Function(Object)) {
+      errorHandler(error);
     } else {
-      (errorHandler as ZoneUnaryCallback)(error);
+      throw ArgumentError(
+        'is nor Function(Object, StackTrace) neither Function(Object)',
+        'errorHandler',
+      );
     }
   }
 

pkgs/async/test/result/result_test.dart

@@ -281,6 +281,29 @@ void main() {
     expect(called, isTrue);
   });
 
+  test('handle typed binary', () {
+    final result = ErrorResult('error', stack);
+    var called = false;
+    void f(Object error, StackTrace stackTrace) {
+      called = true;
+    }
+
+    result.handle(f);
+    expect(called, isTrue);
+  });
+
+  test('handle typed unary', () {
+    final result = ErrorResult('error', stack);
+    var called = false;
+
+    void f(Object error) {
+      called = true;
+    }
+
+    result.handle(f);
+    expect(called, isTrue);
+  });
+
   test('handle unary and binary', () {
     var result = ErrorResult('error', stack);
     var called = false;