error: incorrect function inside `extern` block --> $DIR/issue-91370-foreign-fn-block-impl.rs:5:8 | LL | extern { | ------ `extern` blocks define existing foreign functions and functions inside of them cannot have a body LL | LL | fn f() { | ________^___- | | | | | cannot have a body LL | | LL | | LL | | impl Copy for u8 {} 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