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use core::{any::TypeId, convert, marker::PhantomData};
use crate::CastIdentityBorrowed;
/// Specialized behavior runner (Owned -> Borrowed)
#[derive(Debug)]
pub struct SpecializerBorrowedReturn<T, U, F>(T, F, PhantomData<fn(T) -> U>);
impl<T, U, F> SpecializerBorrowedReturn<T, U, F>
where
F: FnOnce(T) -> U,
T: 'static,
U: CastIdentityBorrowed<U>,
{
/// Create a new specializer with a fallback function.
#[inline(always)]
pub const fn new(params: T, f: F) -> Self {
Self(params, f, PhantomData)
}
/// Specialize on the parameter and the return type of the closure.
///
/// ```rust
/// use specializer::{CastIdentityBorrowed, SpecializerBorrowedReturn};
///
/// fn specialized<'a, T, U>(a: T, b: &'a u32) -> Option<&'a U>
/// where
/// T: 'static,
/// U: 'static,
/// {
/// SpecializerBorrowedReturn::new(a, |_ty| None)
/// .specialize(|int: i32| -> Option<&i32> { Some(&42) })
/// .specialize(|int: u32| -> Option<&u32> { Some(b) })
/// .run()
/// }
///
/// assert_eq!(specialized::<i32, i32>(3, &5), Some(&42));
/// assert_eq!(specialized::<u32, u32>(3, &5), Some(&5));
/// assert_eq!(specialized::<(), u32>((), &5), None);
/// ```
#[inline]
pub fn specialize<P, R>(
self,
f: impl FnOnce(P) -> R,
) -> SpecializerBorrowedReturn<T, U, impl FnOnce(T) -> U>
where
P: 'static,
R: CastIdentityBorrowed<U>,
{
let SpecializerBorrowedReturn(ty, fallback, phantom_data) = self;
let f = |t: T| -> U {
if <R as CastIdentityBorrowed<U>>::is_same()
&& TypeId::of::<T>() == TypeId::of::<P>()
{
let param = crate::cast_identity::<T, P>(t).unwrap();
return crate::cast_identity_borrowed::<R, U>(f(param))
.unwrap();
}
fallback(t)
};
SpecializerBorrowedReturn(ty, f, phantom_data)
}
/// Specialize on the parameter and the return type of the closure, mapping
/// both.
///
/// ```rust
/// use std::convert;
///
/// use specializer::SpecializerBorrowedReturn;
///
/// fn specialized<'a, T, U>(a: T, b: &'a U) -> &'a U
/// where
/// T: 'static + Clone,
/// U: 'static + From<T> + From<u8>,
/// {
/// let to = |ty: T| -> &U { b };
///
/// SpecializerBorrowedReturn::new(a, to)
/// .specialize(|int: i32| -> &i32 { &42 })
/// .specialize_map(
/// |int: u8| int * 3,
/// to,
/// convert::identity::<&U>,
/// )
/// .run()
/// }
///
/// assert_eq!(specialized::<u8, i32>(3, &5), &mut 5);
/// assert_eq!(specialized::<i32, i32>(3, &5), &mut 42);
/// assert_eq!(specialized::<i16, i32>(3, &5), &mut 5);
/// ```
#[inline]
pub fn specialize_map<P, R>(
self,
p: impl FnOnce(P) -> P,
f: impl FnOnce(T) -> U,
r: impl FnOnce(R) -> R,
) -> SpecializerBorrowedReturn<T, U, impl FnOnce(T) -> U>
where
P: 'static,
R: CastIdentityBorrowed<U>,
U: CastIdentityBorrowed<R>,
{
let SpecializerBorrowedReturn(ty, fallback, phantom_data) = self;
let f = |t: T| -> U {
if <U as CastIdentityBorrowed<R>>::is_same()
&& TypeId::of::<T>() == TypeId::of::<P>()
{
let param = crate::cast_identity::<T, P>(t).unwrap();
let param = crate::cast_identity::<P, T>(p(param)).unwrap();
let ret =
crate::cast_identity_borrowed::<U, R>(f(param)).unwrap();
return crate::cast_identity_borrowed::<R, U>(r(ret)).unwrap();
}
fallback(t)
};
SpecializerBorrowedReturn(ty, f, phantom_data)
}
/// Specialize on the parameter of the closure.
///
/// ```rust
/// use specializer::{CastIdentityBorrowed, SpecializerBorrowedReturn};
///
/// fn specialized<'a, T, U>(a: T, b: &'a U) -> Option<&'a U>
/// where
/// T: 'static,
/// U: 'static,
/// {
/// SpecializerBorrowedReturn::new(a, |_ty| None)
/// .specialize_param(|int: u32| Some(b))
/// .run()
/// }
///
/// assert_eq!(specialized::<i32, i32>(3, &5), None);
/// assert_eq!(specialized::<u32, u32>(3, &5), Some(&5));
/// ```
#[inline]
pub fn specialize_param<P>(
self,
f: impl FnOnce(P) -> U,
) -> SpecializerBorrowedReturn<T, U, impl FnOnce(T) -> U>
where
P: 'static,
{
self.specialize::<P, U>(f)
}
/// Specialize on the return type of the closure.
///
/// ```rust
/// use specializer::{CastIdentityBorrowed, SpecializerBorrowedReturn};
///
/// fn specialized<'a, U>(a: i32, b: &'a u32) -> Option<&'a U>
/// where
/// U: 'static,
/// {
/// SpecializerBorrowedReturn::new(a, |_ty| None)
/// .specialize_return(|int| -> Option<&i32> { Some(&42) })
/// .specialize_return(|int| -> Option<&u32> { Some(b) })
/// .run()
/// }
///
/// assert_eq!(specialized(3, &5), Some(&42i32));
/// assert_eq!(specialized(3, &5), Some(&5u32));
/// assert_eq!(specialized::<u8>(3, &5), None);
/// ```
#[inline]
pub fn specialize_return<R>(
self,
f: impl FnOnce(T) -> R,
) -> SpecializerBorrowedReturn<T, U, impl FnOnce(T) -> U>
where
R: CastIdentityBorrowed<U>,
{
self.specialize::<T, R>(f)
}
/// Specialize on the parameter and the return type of the closure, mapping
/// the parameter.
///
/// ```rust
/// use std::convert;
///
/// use specializer::SpecializerBorrowedReturn;
///
/// fn specialized<'a, T, U>(a: T, b: &'a U) -> &'a U
/// where
/// T: 'static + Clone,
/// U: 'static + From<T> + From<u8>,
/// {
/// let to = |ty: T| -> &U { b };
///
/// SpecializerBorrowedReturn::new(a, to)
/// .specialize(|int: i32| -> &i32 { &42 })
/// .specialize_map_param(|int: u8| int * 3, to)
/// .run()
/// }
///
/// let value = 3;
///
/// assert_eq!(specialized::<u8, i32>(3, &5), &mut 5);
/// assert_eq!(specialized::<i32, i32>(3, &5), &mut 42);
/// assert_eq!(specialized::<i16, i32>(3, &5), &mut 5);
/// ```
#[inline]
pub fn specialize_map_param<P>(
self,
p: impl FnOnce(P) -> P,
f: impl FnOnce(T) -> U,
) -> SpecializerBorrowedReturn<T, U, impl FnOnce(T) -> U>
where
P: 'static,
{
self.specialize_map::<P, U>(p, f, convert::identity)
}
/// Specialize on the parameter and the return type of the closure, mapping
/// the parameter.
///
/// ```rust
/// use std::convert;
///
/// use specializer::SpecializerBorrowedReturn;
///
/// fn specialized<'a, U>(a: i8, b: &'a i32, c: &'a U) -> &'a U
/// where
/// U: 'static,
/// {
/// let to = |ty: i8| -> &U { c };
///
/// SpecializerBorrowedReturn::new(a, to)
/// .specialize_return(|int| -> &i8 { &16 })
/// .specialize_map_return(
/// to,
/// |ty| -> &i32 { b },
/// )
/// .specialize_map_return(
/// |ty| -> &U { c },
/// |ty| -> &i16 { &15 },
/// )
/// .run()
/// }
///
/// let value = 3;
///
/// assert_eq!(specialized::<i8>(value, &5, &42), &16);
/// assert_eq!(specialized::<i64>(value, &5, &42), &42);
/// assert_eq!(specialized::<i32>(value, &5, &42), &5);
/// assert_eq!(specialized::<i16>(value, &5, &42), &15);
/// ```
#[inline]
pub fn specialize_map_return<R>(
self,
f: impl FnOnce(T) -> U,
r: impl FnOnce(R) -> R,
) -> SpecializerBorrowedReturn<T, U, impl FnOnce(T) -> U>
where
R: CastIdentityBorrowed<U>,
U: CastIdentityBorrowed<R>,
{
self.specialize_map::<T, R>(convert::identity, f, r)
}
/// Run the specializer.
#[inline]
pub fn run(self) -> U {
(self.1)(self.0)
}
}