undefined_class

Undefined class '{0}'.

The analyzer produces this diagnostic when it encounters an identifier that appears to be the name of a class but either isn't defined or isn't visible in the scope in which it's being referenced.

The following code produces this diagnostic because Piont isn't defined:

class Point {}

void f(Piont p) {}

If the identifier isn't defined, then either define it or replace it with the name of a class that is defined. The example above can be corrected by fixing the spelling of the class:

class Point {}

void f(Point p) {}

If the class is defined but isn't visible, then you probably need to add an import.

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.