variable_type_mismatch

A value of type '{0}' can't be assigned to a const variable of type '{1}'.

The analyzer produces this diagnostic when the evaluation of a constant expression would result in a CastException.

The following code produces this diagnostic because the value of x is an int, which can't be assigned to y because an int isn't a String:

const dynamic x = 0;
const String y = x;

If the declaration of the constant is correct, then change the value being assigned to be of the correct type:

const dynamic x = 0;
const String y = '$x';

If the assigned value is correct, then change the declaration to have the correct type:

const int x = 0;
const int y = x;

Unless stated otherwise, the documentation on this site reflects Dart 3.8.0. Page last updated on 2025-05-08. View source or report an issue.