Rollup merge of #139909 - oli-obk:or-patterns, r=BoxyUwU

implement or-patterns for pattern types

These are necessary to represent `NonZeroI32`, as the range for that is `..0 | 1..`. The `rustc_scalar_layout_range_*` attributes avoided this by just implementing wraparound and having a single `1..=-1` range effectively. See https://rust-lang.zulipchat.com/#narrow/channel/481660-t-lang.2Fpattern-types/topic/.60or.20pattern.60.20representation.20in.20type.20system/with/504217694 for some background discussion

cc https://github.com/rust-lang/rust/issues/123646

r? `@BoxyUwU`

1 files changed, 10 insertions, 5 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics.rs b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
index 40c63f2b250..97d066ffe3f 100644
--- a/compiler/rustc_const_eval/src/interpret/intrinsics.rs
+++ b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
@@ -61,16 +61,21 @@ pub(crate) fn eval_nullary_intrinsic<'tcx>(
             ensure_monomorphic_enough(tcx, tp_ty)?;
             ConstValue::from_u128(tcx.type_id_hash(tp_ty).as_u128())
         }
-        sym::variant_count => match tp_ty.kind() {
+        sym::variant_count => match match tp_ty.kind() {
+            // Pattern types have the same number of variants as their base type.
+            // Even if we restrict e.g. which variants are valid, the variants are essentially just uninhabited.
+            // And `Result<(), !>` still has two variants according to `variant_count`.
+            ty::Pat(base, _) => *base,
+            _ => tp_ty,
+        }
+        .kind()
+        {
             // Correctly handles non-monomorphic calls, so there is no need for ensure_monomorphic_enough.
             ty::Adt(adt, _) => ConstValue::from_target_usize(adt.variants().len() as u64, &tcx),
             ty::Alias(..) | ty::Param(_) | ty::Placeholder(_) | ty::Infer(_) => {
                 throw_inval!(TooGeneric)
             }
-            ty::Pat(_, pat) => match **pat {
-                ty::PatternKind::Range { .. } => ConstValue::from_target_usize(0u64, &tcx),
-                // Future pattern kinds may have more variants
-            },
+            ty::Pat(..) => unreachable!(),
             ty::Bound(_, _) => bug!("bound ty during ctfe"),
             ty::Bool
             | ty::Char