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// Traits where a method is c-variadic are not dyn compatible.
//
// Creating a function pointer from a method on an `&dyn T` value creates a ReifyShim.
// This shim cannot reliably forward C-variadic arguments. Thus the trait as a whole
// is dyn-incompatible to prevent invalid shims from being created.
#![feature(c_variadic)]
#[repr(transparent)]
struct Struct(u64);
trait Trait {
fn get(&self) -> u64;
unsafe extern "C" fn dyn_method_ref(&self, mut ap: ...) -> u64 {
self.get() + unsafe { ap.arg::<u64>() }
}
}
impl Trait for Struct {
fn get(&self) -> u64 {
self.0
}
}
fn main() {
unsafe {
let dyn_object: &dyn Trait = &Struct(64);
//~^ ERROR the trait `Trait` is not dyn compatible
assert_eq!(dyn_object.dyn_method_ref(100), 164);
assert_eq!(
(Trait::dyn_method_ref as unsafe extern "C" fn(_, ...) -> u64)(dyn_object, 100),
164
);
}
}
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