rust: pin-init: rewrite the `#[pinned_drop]` attribute macro using `syn`

Rewrite the attribute macro for implementing `PinnedDrop` using `syn`.
Otherwise no functional changes intended aside from improved error
messages on syntactic and semantical errors. For example:

When missing the `drop` function in the implementation, the old error
was:

    error: no rules expected `)`
     --> tests/ui/compile-fail/pinned_drop/no_fn.rs:6:1
      |
    6 | #[pinned_drop]
      | ^^^^^^^^^^^^^^ no rules expected this token in macro call
      |
    note: while trying to match keyword `fn`
     --> src/macros.rs
      |
      |             fn drop($($sig:tt)*) {
      |             ^^
      = note: this error originates in the attribute macro `pinned_drop` (in Nightly builds, run with -Z macro-backtrace for more info)

And the new one is:

    error[E0046]: not all trait items implemented, missing: `drop`
     --> tests/ui/compile-fail/pinned_drop/no_fn.rs:7:1
      |
    7 | impl PinnedDrop for Foo {}
      | ^^^^^^^^^^^^^^^^^^^^^^^ missing `drop` in implementation
      |
      = help: implement the missing item: `fn drop(self: Pin<&mut Self>, _: OnlyCallFromDrop) { todo!() }`

Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <lossin@kernel.org>

1 files changed, 0 insertions, 28 deletions

diff --git a/rust/pin-init/src/macros.rs b/rust/pin-init/src/macros.rs
index 53ed5ce860fc..b80c95612fd6 100644
--- a/rust/pin-init/src/macros.rs
+++ b/rust/pin-init/src/macros.rs
@@ -503,34 +503,6 @@ pub use ::macros::paste;
 #[cfg(not(kernel))]
 pub use ::paste::paste;
 
-/// Creates a `unsafe impl<...> PinnedDrop for $type` block.
-///
-/// See [`PinnedDrop`] for more information.
-///
-/// [`PinnedDrop`]: crate::PinnedDrop
-#[doc(hidden)]
-#[macro_export]
-macro_rules! __pinned_drop {
-    (
-        @impl_sig($($impl_sig:tt)*),
-        @impl_body(
-            $(#[$($attr:tt)*])*
-            fn drop($($sig:tt)*) {
-                $($inner:tt)*
-            }
-        ),
-    ) => {
-        // SAFETY: TODO.
-        unsafe $($impl_sig)* {
-            // Inherit all attributes and the type/ident tokens for the signature.
-            $(#[$($attr)*])*
-            fn drop($($sig)*, _: $crate::__internal::OnlyCallFromDrop) {
-                $($inner)*
-            }
-        }
-    }
-}
-
 /// This macro first parses the struct definition such that it separates pinned and not pinned
 /// fields. Afterwards it declares the struct and implement the `PinData` trait safely.
 #[doc(hidden)]