error: Name `f` forms or references an illegal self-referential cycle (1/1).
 --> tests/compile-fail/surface_forwardref_self1.rs:5:13
  |
5 |         f = f -> f;
  |             ^

error: Name `f` forms or references an illegal self-referential cycle (1/1).
 --> tests/compile-fail/surface_forwardref_self1.rs:5:18
  |
5 |         f = f -> f;
  |                  ^