Fix for rust 1.57

Some options aren't available for const yet in rust 1.57

src/rust/iced-x86/src/formatter/fast.rs

@@ -29,7 +29,8 @@ use crate::*;
 use alloc::boxed::Box;
 use alloc::vec::Vec;
 use core::marker::PhantomData;
-use core::{mem, ptr, slice};
+use core::{mem, ptr};
+use std::slice;
 
 // full fmt'd str = "prefixes mnemonic op0<decorators1>, op1, op2, op3, op4<decorators2>"
 // prefixes = "es xacquire xrelease lock notrack repe repne "
@@ -114,7 +115,7 @@ impl<const SIZE: usize> FastString<SIZE> {
 		let required_size = 1 + SIZE;
 		assert!(len_data.len() >= required_size);
 		assert!(len_data[0] as usize <= SIZE);
-		let len_data = unsafe { &*(len_data.as_ptr() as *const FastStringRepr<SIZE>) };
+		let len_data: &'static FastStringRepr<SIZE> = unsafe { mem::transmute(len_data.as_ptr()) };
 		Self::new(len_data)
 	}
 
@@ -131,7 +132,7 @@ impl<const SIZE: usize> FastString<SIZE> {
 	}
 
 	#[allow(dead_code)]
-	const fn get_slice(self) -> &'static [u8] {
+	fn get_slice(self) -> &'static [u8] {
 		unsafe { slice::from_raw_parts(self.utf8_data(), self.len()) }
 	}
 }