void_checks

Assignment to a variable of type 'void'.

The analyzer produces this diagnostic when a value is assigned to a variable of type void.

It isn't possible to access the value of such a variable, so the assignment has no value.

The following code produces this diagnostic because the field value has the type void, but a value is being assigned to it:

class A<T> {
  T? value;
}

void f(A<void> a) {
  a.value = 1;
}

The following code produces this diagnostic because the type of the parameter p in the method m is void, but a value is being assigned to it in the invocation:

class A<T> {
  void m(T p) { }
}

void f(A<void> a) {
  a.m(1);
}

If the type of the variable is incorrect, then change the type of the variable:

class A<T> {
  T? value;
}

void f(A<int> a) {
  a.value = 1;
}

If the type of the variable is correct, then remove the assignment:

class A<T> {
  T? value;
}

void f(A<void> a) {}

Unless stated otherwise, the documentation on this site reflects Dart 3.8.1. Page last updated on 2025-05-08. View source or report an issue.