| error: incorrect function inside `extern` block | 
 |   --> $DIR/issue-91370-foreign-fn-block-impl.rs:5:8 | 
 |    | | 
 | LL |   extern "C" { | 
 |    |   ---------- `extern` blocks define existing foreign functions and functions inside of them cannot have a body | 
 | LL | | 
 | LL |       fn f() { | 
 |    |  ________^___- | 
 |    | |        | | 
 |    | |        cannot have a body | 
 | ...  | | 
 | LL | |     } | 
 |    | |_____- help: remove the invalid body: `;` | 
 |    | | 
 |    = help: you might have meant to write a function accessible through FFI, which can be done by writing `extern fn` outside of the `extern` block | 
 |    = note: for more information, visit https://doc.rust-lang.org/std/keyword.extern.html | 
 |  | 
 | error: aborting due to 1 previous error | 
 |  |