error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
  --> $DIR/issue-66286.rs:8:26
   |
LL | pub extern "C" fn foo(_: Vec(u32)) -> u32 {
   |                          ^^^^^^^^ only `Fn` traits may use parentheses
   |
help: use angle brackets instead
   |
LL - pub extern "C" fn foo(_: Vec(u32)) -> u32 {
LL + pub extern "C" fn foo(_: Vec<u32>) -> u32 {
   |

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0214`.