Function ptr_metadata 

pub const fn ptr_metadata<P, M>(ptr: *const P) -> M
where
    P: Pointee<Metadata = M> + ?Sized,

🔬This is a nightly-only experimental API. (core_intrinsics)

This item is validated for IEC 61508 (SIL 2) and ISO 26262 (ASIL B).

Lowers in MIR to Rvalue::UnaryOp with UnOp::PtrMetadata.

This is used to implement functions like ptr::metadata.