assignment_to_const

Constant variables can't be assigned a value after initialization.

The analyzer produces this diagnostic when it finds an assignment to a top-level variable, a static field, or a local variable that has the const modifier. The value of a compile-time constant can't be changed at runtime.

The following code produces this diagnostic because c is being assigned a value even though it has the const modifier:

const c = 0;

void f() {
  c = 1;
  print(c);
}

If the variable must be assignable, then remove the const modifier:

var c = 0;

void f() {
  c = 1;
  print(c);
}

If the constant shouldn't be changed, then either remove the assignment or use a local variable in place of references to the constant:

const c = 0;

void f() {
  var v = 1;
  print(v);
}

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.