Vendor things

third-party/vendor/salsa-2022/src/id.rs

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+use std::fmt::Debug;
+use std::hash::Hash;
+use std::num::NonZeroU32;
+
+/// An Id is a newtype'd u32 ranging from `0..Id::MAX_U32`.
+/// The maximum range is smaller than a standard u32 to leave
+/// room for niches; currently there is only one niche, so that
+/// `Option<Id>` is the same size as an `Id`.
+///
+/// You will rarely use the `Id` type directly, though you can.
+/// You are more likely to use types that implement the `AsId` trait,
+/// such as entity keys.
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub struct Id {
+    value: NonZeroU32,
+}
+
+impl Id {
+    pub const MAX_U32: u32 = std::u32::MAX - 0xFF;
+    pub const MAX_USIZE: usize = Self::MAX_U32 as usize;
+
+    /// Create a `salsa::Id` from a u32 value. This value should
+    /// be less than [`Self::MAX_U32`].
+    ///
+    /// In general, you should not need to create salsa ids yourself,
+    /// but it can be useful if you are using the type as a general
+    /// purpose "identifier" internally.
+    #[track_caller]
+    pub const fn from_u32(x: u32) -> Self {
+        Id {
+            value: match NonZeroU32::new(x + 1) {
+                Some(v) => v,
+                None => panic!("given value is too large to be a `salsa::Id`"),
+            },
+        }
+    }
+
+    pub const fn as_u32(self) -> u32 {
+        self.value.get() - 1
+    }
+}
+
+impl From<u32> for Id {
+    fn from(n: u32) -> Self {
+        Id::from_u32(n)
+    }
+}
+
+impl From<usize> for Id {
+    fn from(n: usize) -> Self {
+        assert!(n < Id::MAX_USIZE);
+        Id::from_u32(n as u32)
+    }
+}
+
+impl From<Id> for u32 {
+    fn from(n: Id) -> Self {
+        n.as_u32()
+    }
+}
+
+impl From<Id> for usize {
+    fn from(n: Id) -> usize {
+        n.as_u32() as usize
+    }
+}
+
+/// Trait for types that can be interconverted to a salsa Id;
+pub trait AsId: Sized + Copy + Eq + Hash + Debug {
+    fn as_id(self) -> Id;
+    fn from_id(id: Id) -> Self;
+}
+
+impl AsId for Id {
+    fn as_id(self) -> Id {
+        self
+    }
+
+    fn from_id(id: Id) -> Self {
+        id
+    }
+}
+
+/// As a special case, we permit `()` to be converted to an `Id`.
+/// This is useful for declaring functions with no arguments.
+impl AsId for () {
+    fn as_id(self) -> Id {
+        Id::from_u32(0)
+    }
+
+    fn from_id(id: Id) -> Self {
+        assert_eq!(0, id.as_u32());
+    }
+}