Rollup merge of #73778 - nbdd0121:const_likely, r=oli-obk

[rust.git] / src / libcore / intrinsics.rs

diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs
index da174299fb9af4f8bc4c3778b725c0e259009e2e..57ffed19c0085d29c7c7441f672f6a7103e3f12a 100644 (file)
--- a/src/libcore/intrinsics.rs
+++ b/src/libcore/intrinsics.rs
@@ -1919,6 +1919,15 @@
     #[rustc_const_unstable(feature = "const_discriminant", issue = "69821")]
     pub fn discriminant_value<T>(v: &T) -> <T as DiscriminantKind>::Discriminant;
 
+    /// Returns the number of variants of the type `T` cast to a `usize`;
+    /// if `T` has no variants, returns 0. Uninhabited variants will be counted.
+    ///
+    /// The to-be-stabilized version of this intrinsic is
+    /// [`std::mem::variant_count`](../../std/mem/fn.variant_count.html)
+    #[rustc_const_unstable(feature = "variant_count", issue = "73662")]
+    #[cfg(not(bootstrap))]
+    pub fn variant_count<T>() -> usize;
+
     /// Rust's "try catch" construct which invokes the function pointer `try_fn`
     /// with the data pointer `data`.
     ///
@@ -1962,6 +1971,12 @@
     pub fn ptr_guaranteed_ne<T>(ptr: *const T, other: *const T) -> bool;
 }
 
+#[rustc_const_unstable(feature = "variant_count", issue = "73662")]
+#[cfg(bootstrap)]
+pub const fn variant_count<T>() -> usize {
+    0
+}
+
 // Some functions are defined here because they accidentally got made
 // available in this module on stable. See <https://github.com/rust-lang/rust/issues/15702>.
 // (`transmute` also falls into this category, but it cannot be wrapped due to the