Fn is assumed when reference is passed as Pattern · Issue #79359 · rust-lang/rust (original) (raw)

Sorry, I don't exactly understand why this happened, so I can't provide much more detail.

error[E0277]: expected a `std::ops::Fn<(char,)>` closure, found `char`
  --> hglfgp_glsl/src/lib.rs:21:42
   |
21 |     s.chars().filter(|c| !(" \n\t".contains(c))).collect::<String>()
   |                                             ^ expected an `Fn<(char,)>` closure, found `char`

The correct solution to fix this was to change |c| to |&c|, however the error message did not indicate what was wrong at all.
Please inform me if I need to change the format of this issue.