memory_encryption: rewrite const_fn calls to re-use old feature

Author: zyuiop

Cargo.toml

@@ -24,7 +24,7 @@ bit_field = "0.10.1"
 bitflags = "2.3.2"
 volatile = "0.4.4"
 rustversion = "1.0.5"
-const_fn = "0.4.11"
+const_fn = { optional = true, version = "0.4.11" }
 
 [features]
 default = ["nightly", "instructions"]
@@ -33,7 +33,6 @@ memory_encryption = []
 nightly = ["const_fn", "step_trait", "abi_x86_interrupt", "asm_const"]
 abi_x86_interrupt = []
 # deprecated, no longer needed
-const_fn = []
 asm_const = []
 step_trait = []
 doc_auto_cfg = []

src/addr.rs

@@ -5,7 +5,6 @@ use crate::structures::mem_encrypt::ENC_BIT_MASK;
 use crate::structures::paging::page_table::PageTableLevel;
 use crate::structures::paging::{PageOffset, PageTableIndex};
 use bit_field::BitField;
-use const_fn::const_fn;
 use core::convert::TryFrom;
 use core::fmt;
 #[cfg(feature = "step_trait")]
@@ -446,7 +445,7 @@ impl PhysAddr {
     /// If the `memory_encryption` feature is available and has been enabled, this function also
     /// panics fails if the encryption bit is manually set in the address.
     #[inline]
-    #[const_fn(cfg(not(feature = "memory_encryption")))]
+    #[cfg_attr(all(not(feature = "memory_encryption"), feature = "const_fn"), const_fn::const_fn)]
     pub const fn new(addr: u64) -> Self {
         // TODO: Replace with .ok().expect(msg) when that works on stable.
         match Self::try_new(addr) {
@@ -471,7 +470,7 @@ impl PhysAddr {
     /// If the `memory_encryption` feature is available and has been enabled, this also fails if the
     /// encryption bit is manually set in the address.
     #[inline]
-    #[const_fn(cfg(not(feature = "memory_encryption")))]
+    #[cfg_attr(all(not(feature = "memory_encryption"), feature = "const_fn"), const_fn::const_fn)]
     pub const fn try_new(addr: u64) -> Result<Self, PhysAddrNotValid> {
         let p = Self::new_truncate(addr);
         if p.0 == addr {

src/structures/paging/page_table.rs

@@ -3,7 +3,6 @@
 use super::{PageSize, PhysFrame, Size4KiB};
 use crate::addr::PhysAddr;
 use bitflags::bitflags;
-use const_fn::const_fn;
 use core::fmt;
 #[cfg(feature = "step_trait")]
 use core::iter::Step;
@@ -53,7 +52,7 @@ impl PageTableEntry {
 
     /// Returns the flags of this entry.
     #[inline]
-    #[const_fn(cfg(not(feature = "memory_encryption")))]
+    #[cfg_attr(all(not(feature = "memory_encryption"), feature = "const_fn"), const_fn::const_fn)]
     pub const fn flags(&self) -> PageTableFlags {
         PageTableFlags::from_bits_retain(self.entry & !Self::physical_address_mask())
     }