1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288
/// Implements [`Tag`] for a given type.
///
/// You can use `impl_tag` on structs and enums.
/// You need to specify the type and all its possible values,
/// which can only be paths with optional fields.
///
/// [`Tag`]: crate::tagged_ptr::Tag
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// #![feature(macro_metavar_expr)]
/// use rustc_data_structures::{impl_tag, tagged_ptr::Tag};
///
/// #[derive(Copy, Clone, PartialEq, Debug)]
/// enum SomeTag {
/// A,
/// B,
/// X { v: bool },
/// Y(bool, bool),
/// }
///
/// impl_tag! {
/// // The type for which the `Tag` will be implemented
/// impl Tag for SomeTag;
/// // You need to specify all possible tag values:
/// SomeTag::A, // 0
/// SomeTag::B, // 1
/// // For variants with fields, you need to specify the fields:
/// SomeTag::X { v: true }, // 2
/// SomeTag::X { v: false }, // 3
/// // For tuple variants use named syntax:
/// SomeTag::Y { 0: true, 1: true }, // 4
/// SomeTag::Y { 0: false, 1: true }, // 5
/// SomeTag::Y { 0: true, 1: false }, // 6
/// SomeTag::Y { 0: false, 1: false }, // 7
/// }
///
/// // Tag values are assigned in order:
/// assert_eq!(SomeTag::A.into_usize(), 0);
/// assert_eq!(SomeTag::X { v: false }.into_usize(), 3);
/// assert_eq!(SomeTag::Y(false, true).into_usize(), 5);
///
/// assert_eq!(unsafe { SomeTag::from_usize(1) }, SomeTag::B);
/// assert_eq!(unsafe { SomeTag::from_usize(2) }, SomeTag::X { v: true });
/// assert_eq!(unsafe { SomeTag::from_usize(7) }, SomeTag::Y(false, false));
/// ```
///
/// Structs are supported:
///
/// ```
/// #![feature(macro_metavar_expr)]
/// # use rustc_data_structures::impl_tag;
/// #[derive(Copy, Clone)]
/// struct Flags { a: bool, b: bool }
///
/// impl_tag! {
/// impl Tag for Flags;
/// Flags { a: true, b: true },
/// Flags { a: false, b: true },
/// Flags { a: true, b: false },
/// Flags { a: false, b: false },
/// }
/// ```
///
/// Not specifying all values results in a compile error:
///
/// ```compile_fail,E0004
/// #![feature(macro_metavar_expr)]
/// # use rustc_data_structures::impl_tag;
/// #[derive(Copy, Clone)]
/// enum E {
/// A,
/// B,
/// }
///
/// impl_tag! {
/// impl Tag for E;
/// E::A,
/// }
/// ```
#[cfg(bootstrap)]
#[macro_export]
macro_rules! impl_tag {
(
impl Tag for $Self:ty;
$(
$($path:ident)::* $( { $( $fields:tt )* })?,
)*
) => {
// Safety:
// `bits_for_tags` is called on the same `${index()}`-es as
// `into_usize` returns, thus `BITS` constant is correct.
unsafe impl $crate::tagged_ptr::Tag for $Self {
const BITS: u32 = $crate::tagged_ptr::bits_for_tags(&[
$(
${index()},
$( ${ignore(path)} )*
)*
]);
#[inline]
fn into_usize(self) -> usize {
// This forbids use of repeating patterns (`Enum::V`&`Enum::V`, etc)
// (or at least it should, see <https://github.com/rust-lang/rust/issues/110613>)
#[forbid(unreachable_patterns)]
match self {
// `match` is doing heavy lifting here, by requiring exhaustiveness
$(
$($path)::* $( { $( $fields )* } )? => ${index()},
)*
}
}
#[inline]
unsafe fn from_usize(tag: usize) -> Self {
match tag {
$(
${index()} => $($path)::* $( { $( $fields )* } )?,
)*
// Safety:
// `into_usize` only returns `${index()}` of the same
// repetition as we are filtering above, thus if this is
// reached, the safety contract of this function was
// already breached.
_ => unsafe {
debug_assert!(
false,
"invalid tag: {tag}\
(this is a bug in the caller of `from_usize`)"
);
std::hint::unreachable_unchecked()
},
}
}
}
};
}
/// Implements [`Tag`] for a given type.
///
/// You can use `impl_tag` on structs and enums.
/// You need to specify the type and all its possible values,
/// which can only be paths with optional fields.
///
/// [`Tag`]: crate::tagged_ptr::Tag
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// #![feature(macro_metavar_expr)]
/// use rustc_data_structures::{impl_tag, tagged_ptr::Tag};
///
/// #[derive(Copy, Clone, PartialEq, Debug)]
/// enum SomeTag {
/// A,
/// B,
/// X { v: bool },
/// Y(bool, bool),
/// }
///
/// impl_tag! {
/// // The type for which the `Tag` will be implemented
/// impl Tag for SomeTag;
/// // You need to specify all possible tag values:
/// SomeTag::A, // 0
/// SomeTag::B, // 1
/// // For variants with fields, you need to specify the fields:
/// SomeTag::X { v: true }, // 2
/// SomeTag::X { v: false }, // 3
/// // For tuple variants use named syntax:
/// SomeTag::Y { 0: true, 1: true }, // 4
/// SomeTag::Y { 0: false, 1: true }, // 5
/// SomeTag::Y { 0: true, 1: false }, // 6
/// SomeTag::Y { 0: false, 1: false }, // 7
/// }
///
/// // Tag values are assigned in order:
/// assert_eq!(SomeTag::A.into_usize(), 0);
/// assert_eq!(SomeTag::X { v: false }.into_usize(), 3);
/// assert_eq!(SomeTag::Y(false, true).into_usize(), 5);
///
/// assert_eq!(unsafe { SomeTag::from_usize(1) }, SomeTag::B);
/// assert_eq!(unsafe { SomeTag::from_usize(2) }, SomeTag::X { v: true });
/// assert_eq!(unsafe { SomeTag::from_usize(7) }, SomeTag::Y(false, false));
/// ```
///
/// Structs are supported:
///
/// ```
/// #![feature(macro_metavar_expr)]
/// # use rustc_data_structures::impl_tag;
/// #[derive(Copy, Clone)]
/// struct Flags { a: bool, b: bool }
///
/// impl_tag! {
/// impl Tag for Flags;
/// Flags { a: true, b: true },
/// Flags { a: false, b: true },
/// Flags { a: true, b: false },
/// Flags { a: false, b: false },
/// }
/// ```
///
/// Not specifying all values results in a compile error:
///
/// ```compile_fail,E0004
/// #![feature(macro_metavar_expr)]
/// # use rustc_data_structures::impl_tag;
/// #[derive(Copy, Clone)]
/// enum E {
/// A,
/// B,
/// }
///
/// impl_tag! {
/// impl Tag for E;
/// E::A,
/// }
/// ```
#[cfg(not(bootstrap))]
#[macro_export]
macro_rules! impl_tag {
(
impl Tag for $Self:ty;
$(
$($path:ident)::* $( { $( $fields:tt )* })?,
)*
) => {
// Safety:
// `bits_for_tags` is called on the same `${index()}`-es as
// `into_usize` returns, thus `BITS` constant is correct.
unsafe impl $crate::tagged_ptr::Tag for $Self {
const BITS: u32 = $crate::tagged_ptr::bits_for_tags(&[
$(
${index()},
$( ${ignore($path)} )*
)*
]);
#[inline]
fn into_usize(self) -> usize {
// This forbids use of repeating patterns (`Enum::V`&`Enum::V`, etc)
// (or at least it should, see <https://github.com/rust-lang/rust/issues/110613>)
#[forbid(unreachable_patterns)]
match self {
// `match` is doing heavy lifting here, by requiring exhaustiveness
$(
$($path)::* $( { $( $fields )* } )? => ${index()},
)*
}
}
#[inline]
unsafe fn from_usize(tag: usize) -> Self {
match tag {
$(
${index()} => $($path)::* $( { $( $fields )* } )?,
)*
// Safety:
// `into_usize` only returns `${index()}` of the same
// repetition as we are filtering above, thus if this is
// reached, the safety contract of this function was
// already breached.
_ => unsafe {
debug_assert!(
false,
"invalid tag: {tag}\
(this is a bug in the caller of `from_usize`)"
);
std::hint::unreachable_unchecked()
},
}
}
}
};
}
#[cfg(test)]
mod tests;