tests/ui/proc-macro/signature.stderr

   1 error[E0277]: expected a `Fn<(proc_macro::TokenStream,)>` closure, found `unsafe extern "C" fn(i32, u32) -> u32 {foo}`
   2   --> $DIR/signature.rs:10:1
   3    |
   4 LL | / pub unsafe extern "C" fn foo(a: i32, b: u32) -> u32 {
   5 LL | |
   6 LL | |     loop {}
   7 LL | | }
   8    | | ^
   9    | | |
  10    | |_call the function in a closure: `|| unsafe { /* code */ }`
  11    |   required by a bound introduced by this call
  12    |
  13    = help: the trait `Fn<(proc_macro::TokenStream,)>` is not implemented for fn item `unsafe extern "C" fn(i32, u32) -> u32 {foo}`
  14    = note: unsafe function cannot be called generically without an unsafe block
  15 note: required by a bound in `ProcMacro::custom_derive`
  16   --> $SRC_DIR/proc_macro/src/bridge/client.rs:LL:COL
  17
  18 error: aborting due to previous error
  19
  20 For more information about this error, try `rustc --explain E0277`.