Revision control
Copy as Markdown
Other Tools
macro_rules! if_downcast_into {
($in_ty:ty, $out_ty:ty, $val:ident, $body:expr) => ({
if std::any::TypeId::of::<$in_ty>() == std::any::TypeId::of::<$out_ty>() {
// Store the value in an `Option` so we can `take`
// it after casting to `&mut dyn Any`.
let mut slot = Some($val);
// Re-write the `$val` ident with the downcasted value.
let $val = (&mut slot as &mut dyn std::any::Any)
.downcast_mut::<Option<$out_ty>>()
.unwrap()
.take()
.unwrap();
// Run the $body in scope of the replaced val.
$body
}
})
}