ffi_native_unexpected_number_of_parameters

Unexpected number of Native annotation parameters. Expected {0} but has {1}.

The analyzer produces this diagnostic when the number of parameters in the function type used as a type argument for the @Native annotation doesn't match the number of parameters in the function being annotated.

The following code produces this diagnostic because the function type used as a type argument for the @Native annotation (Void Function(Double)) has one argument and the type of the annotated function (void f(double, double)) has two arguments:

import 'dart:ffi';

@Native<Void Function(Double)>(symbol: 'f')
external void f(double x, double y);

If the annotated function is correct, then update the function type in the @Native annotation to match:

import 'dart:ffi';

@Native<Void Function(Double, Double)>(symbol: 'f')
external void f(double x, double y);

If the function type in the @Native annotation is correct, then update the annotated function to match:

import 'dart:ffi';

@Native<Void Function(Double)>(symbol: 'f')
external void f(double x);

Unless stated otherwise, the documentation on this site reflects Dart 3.7.3. Page last updated on 2025-05-08. View source or report an issue.