Remove IdFunctor trait.

It's defined in `rustc_data_structures` but is only used in
`rustc_type_ir`. The code is shorter and easier to read if we remove
this layer of abstraction and just do the things directly where they are
needed.

compiler/rustc_data_structures/src/functor.rs

@@ -1,116 +0,0 @@
-use rustc_index::{Idx, IndexVec};
-use std::{mem, rc::Rc, sync::Arc};
-
-pub trait IdFunctor: Sized {
-    type Inner;
-
-    fn try_map_id<F, E>(self, f: F) -> Result<Self, E>
-    where
-        F: FnMut(Self::Inner) -> Result<Self::Inner, E>;
-}
-
-impl<T> IdFunctor for Box<T> {
-    type Inner = T;
-
-    #[inline]
-    fn try_map_id<F, E>(self, mut f: F) -> Result<Self, E>
-    where
-        F: FnMut(Self::Inner) -> Result<Self::Inner, E>,
-    {
-        let raw = Box::into_raw(self);
-        Ok(unsafe {
-            // SAFETY: The raw pointer points to a valid value of type `T`.
-            let value = raw.read();
-            // SAFETY: Converts `Box<T>` to `Box<MaybeUninit<T>>` which is the
-            // inverse of `Box::assume_init()` and should be safe.
-            let raw: Box<mem::MaybeUninit<T>> = Box::from_raw(raw.cast());
-            // SAFETY: Write the mapped value back into the `Box`.
-            Box::write(raw, f(value)?)
-        })
-    }
-}
-
-impl<T> IdFunctor for Vec<T> {
-    type Inner = T;
-
-    #[inline]
-    fn try_map_id<F, E>(self, f: F) -> Result<Self, E>
-    where
-        F: FnMut(Self::Inner) -> Result<Self::Inner, E>,
-    {
-        self.into_iter().map(f).collect()
-    }
-}
-
-impl<T> IdFunctor for Box<[T]> {
-    type Inner = T;
-
-    #[inline]
-    fn try_map_id<F, E>(self, f: F) -> Result<Self, E>
-    where
-        F: FnMut(Self::Inner) -> Result<Self::Inner, E>,
-    {
-        Vec::from(self).try_map_id(f).map(Into::into)
-    }
-}
-
-impl<I: Idx, T> IdFunctor for IndexVec<I, T> {
-    type Inner = T;
-
-    #[inline]
-    fn try_map_id<F, E>(self, f: F) -> Result<Self, E>
-    where
-        F: FnMut(Self::Inner) -> Result<Self::Inner, E>,
-    {
-        self.raw.try_map_id(f).map(IndexVec::from_raw)
-    }
-}
-
-macro_rules! rc {
-    ($($rc:ident),+) => {$(
-        impl<T: Clone> IdFunctor for $rc<T> {
-            type Inner = T;
-
-            #[inline]
-            fn try_map_id<F, E>(mut self, mut f: F) -> Result<Self, E>
-            where
-                F: FnMut(Self::Inner) -> Result<Self::Inner, E>,
-            {
-                // We merely want to replace the contained `T`, if at all possible,
-                // so that we don't needlessly allocate a new `$rc` or indeed clone
-                // the contained type.
-                unsafe {
-                    // First step is to ensure that we have a unique reference to
-                    // the contained type, which `$rc::make_mut` will accomplish (by
-                    // allocating a new `$rc` and cloning the `T` only if required).
-                    // This is done *before* casting to `$rc<ManuallyDrop<T>>` so that
-                    // panicking during `make_mut` does not leak the `T`.
-                    $rc::make_mut(&mut self);
-
-                    // Casting to `$rc<ManuallyDrop<T>>` is safe because `ManuallyDrop`
-                    // is `repr(transparent)`.
-                    let ptr = $rc::into_raw(self).cast::<mem::ManuallyDrop<T>>();
-                    let mut unique = $rc::from_raw(ptr);
-
-                    // Call to `$rc::make_mut` above guarantees that `unique` is the
-                    // sole reference to the contained value, so we can avoid doing
-                    // a checked `get_mut` here.
-                    let slot = $rc::get_mut_unchecked(&mut unique);
-
-                    // Semantically move the contained type out from `unique`, fold
-                    // it, then move the folded value back into `unique`. Should
-                    // folding fail, `ManuallyDrop` ensures that the "moved-out"
-                    // value is not re-dropped.
-                    let owned = mem::ManuallyDrop::take(slot);
-                    let folded = f(owned)?;
-                    *slot = mem::ManuallyDrop::new(folded);
-
-                    // Cast back to `$rc<T>`.
-                    Ok($rc::from_raw($rc::into_raw(unique).cast()))
-                }
-            }
-        }
-    )+};
-}
-
-rc! { Rc, Arc }

compiler/rustc_data_structures/src/lib.rs

@@ -18,14 +18,12 @@
 #![feature(min_specialization)]
 #![feature(never_type)]
 #![feature(type_alias_impl_trait)]
-#![feature(new_uninit)]
 #![feature(lazy_cell)]
 #![feature(rustc_attrs)]
 #![feature(negative_impls)]
 #![feature(test)]
 #![feature(thread_id_value)]
 #![feature(allocator_api)]
-#![feature(get_mut_unchecked)]
 #![feature(lint_reasons)]
 #![feature(unwrap_infallible)]
 #![feature(strict_provenance)]
@@ -61,7 +59,6 @@ pub mod binary_search_util;
 pub mod captures;
 pub mod flat_map_in_place;
 pub mod flock;
-pub mod functor;
 pub mod fx;
 pub mod graph;
 pub mod intern;