error: `tee` must have exactly 1 input(s), actually has 0.
 --> tests/compile-fail/surface_degenerate_tee.rs:5:9
  |
5 |         tee();
  |         ^^^^^

warning: `tee` should have at least 2 output(s), actually has 0.
 --> tests/compile-fail/surface_degenerate_tee.rs:5:9
  |
5 |         tee();
  |         ^^^^^