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//! Closure type (equivalent to `&mut dyn FnMut(A) -> R`) that's `repr(C)`.
use std::marker::PhantomData;
#[repr(C)]
pub struct Closure<'a, A, R> {
call: unsafe extern "C" fn(*mut Env, A) -> R,
env: *mut Env,
// Prevent Send and Sync impls. `!Send`/`!Sync` is the usual way of doing
// this, but that requires unstable features. rust-analyzer uses this code
// and avoids unstable features.
//
// The `'a` lifetime parameter represents the lifetime of `Env`.
_marker: PhantomData<*mut &'a mut ()>,
}
struct Env;
impl<'a, A, R, F: FnMut(A) -> R> From<&'a mut F> for Closure<'a, A, R> {
fn from(f: &'a mut F) -> Self {
unsafe extern "C" fn call<A, R, F: FnMut(A) -> R>(env: *mut Env, arg: A) -> R {
(*(env as *mut _ as *mut F))(arg)
}
Closure { call: call::<A, R, F>, env: f as *mut _ as *mut Env, _marker: PhantomData }
}
}
impl<'a, A, R> Closure<'a, A, R> {
pub fn call(&mut self, arg: A) -> R {
unsafe { (self.call)(self.env, arg) }
}
}
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