[pointer] Remove Ptr::project method (#2339)

Now that #1122 is complete in #1896, `project` is redundant.

gherrit-pr-id: I15d38f2f1fffad82caa70ea6eb18dffcd6504495

Author: joshlf

src/pointer/ptr.rs

@@ -1077,32 +1077,6 @@ mod _casts {
 mod _project {
     use super::*;
 
-    impl<'a, T: ?Sized, I> Ptr<'a, Initialized<T>, I>
-    where
-        I: Invariants,
-    {
-        /// Projects a field from `self`.
-        ///
-        /// # Safety
-        ///
-        /// `project` has the same safety preconditions as
-        /// `cast_unsized_unchecked`.
-        #[doc(hidden)]
-        #[inline]
-        pub unsafe fn project<W: 'a + ?Sized>(
-            self,
-            projector: impl FnOnce(*mut T) -> *mut W,
-        ) -> Ptr<'a, Initialized<W>, (I::Aliasing, Unknown)> {
-            // TODO(#1122): If `cast_unsized` were able to reason that, when
-            // casting from an `Initialized` pointer, the result is another
-            // `Initialized` pointer, we could remove this method entirely.
-
-            // SAFETY: This method has the same safety preconditions as
-            // `cast_unsized_unchecked`.
-            unsafe { self.cast_unsized_unchecked(projector) }
-        }
-    }
-
     impl<V, T, I> Ptr<'_, V, I>
     where
         V: Validity<Inner = [T]>,

zerocopy-derive/src/enum.rs

@@ -349,7 +349,7 @@ pub(crate) fn derive_is_bit_valid(
             //   subfield pointer just points to a smaller portion of the
             //   overall struct.
             let variants = unsafe {
-                raw_enum.project(|p: *mut ___ZerocopyRawEnum #ty_generics| {
+                raw_enum.cast_unsized_unchecked(|p: *mut ___ZerocopyRawEnum #ty_generics| {
                     core_reexport::ptr::addr_of_mut!((*p).variants)
                 })
             };

zerocopy-derive/src/lib.rs

@@ -571,7 +571,7 @@ fn derive_try_from_bytes_struct(
                         let project = |slf: *mut Self|
                             ::zerocopy::util::macro_util::core_reexport::ptr::addr_of_mut!((*slf).#field_names);
 
-                        candidate.reborrow().project(project)
+                        candidate.reborrow().cast_unsized_unchecked(project)
                     };
 
                     <#field_tys as ::zerocopy::TryFromBytes>::is_bit_valid(field_candidate)
@@ -629,7 +629,7 @@ fn derive_try_from_bytes_union(
                         let project = |slf: *mut Self|
                             ::zerocopy::util::macro_util::core_reexport::ptr::addr_of_mut!((*slf).#field_names);
 
-                        candidate.reborrow().project(project)
+                        candidate.reborrow().cast_unsized_unchecked(project)
                     };
 
                     <#field_tys as ::zerocopy::TryFromBytes>::is_bit_valid(field_candidate)