feat: Make generating const function with mutable reference behind a …

…feature flag

Turns out it was just stabilized, and will be on Rust 1.83.0

Cargo.toml

@@ -38,7 +38,8 @@ default = []
 serde = ["bitflags-attr-macros/serde"]
 # Allows to use custom types as parameter for the bitflags macro
 custom-types = ["bitflags-attr-macros/custom-types"]
-
+# Generate as const functions some functions that take `&mut` (Only stable on rust 1.83.0: release date: 28 November, 2024)
+const-mut-ref = ["bitflags-attr-macros/const-mut-ref"]
 
 [workspace]
 members = ["bitflags-attr-macros"]

bitflags-attr-macros/Cargo.toml

@@ -32,3 +32,5 @@ default = []
 serde = []
 # Allows to use custom types as parameter for the bitflags macro
 custom-types = []
+# Generate as const functions some functions that take `&mut` (Only stable on rust 1.83.0: release date: 28 November, 2024)
+const-mut-ref = []

bitflags-attr-macros/src/lib.rs

@@ -133,6 +133,12 @@ fn bitflag_impl(attr: TokenStream, item: TokenStream) -> Result<TokenStream> {
         Ident::new(&ty_name, span)
     };
 
+    let const_mut = if cfg!(feature = "const-mut-ref") {
+        quote!(mut)
+    } else {
+        quote!()
+    };
+
     let number_flags = item.variants.len();
 
     let mut all_flags = Vec::with_capacity(number_flags);
@@ -607,20 +613,20 @@ fn bitflag_impl(attr: TokenStream, item: TokenStream) -> Result<TokenStream> {
             /// Set the flags in `other` in the value.
             #[inline]
             #[doc(alias = "insert")]
-            pub const fn set(&mut self, other: Self) {
+            pub #const_mut fn set(&mut self, other: Self) {
                 self.0 = self.or(other).0
             }
 
             /// Unset the flags in `other` in the value.
             #[inline]
             #[doc(alias = "remove")]
-            pub const fn unset(&mut self, other: Self) {
+            pub #const_mut fn unset(&mut self, other: Self) {
                 self.0 = self.difference(other).0
             }
 
             /// Toggle the flags in `other` in the value.
             #[inline]
-            pub const fn toggle(&mut self, other: Self) {
+            pub #const_mut const fn toggle(&mut self, other: Self) {
                 self.0 = self.xor(other).0
             }
         }