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.