Use generic NonZero internally.

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -5,7 +5,7 @@
 //! to be const-safe.
 
 use std::fmt::Write;
-use std::num::NonZeroUsize;
+use std::num::NonZero;
 
 use either::{Left, Right};
 
@@ -782,7 +782,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
     fn visit_union(
         &mut self,
         op: &OpTy<'tcx, M::Provenance>,
-        _fields: NonZeroUsize,
+        _fields: NonZero<usize>,
     ) -> InterpResult<'tcx> {
         // Special check for CTFE validation, preventing `UnsafeCell` inside unions in immutable memory.
         if self.ctfe_mode.is_some_and(|c| !c.allow_immutable_unsafe_cell()) {

compiler/rustc_const_eval/src/interpret/visitor.rs

@@ -7,7 +7,7 @@ use rustc_middle::ty;
 use rustc_target::abi::FieldIdx;
 use rustc_target::abi::{FieldsShape, VariantIdx, Variants};
 
-use std::num::NonZeroUsize;
+use std::num::NonZero;
 
 use super::{InterpCx, MPlaceTy, Machine, Projectable};
 
@@ -43,7 +43,7 @@ pub trait ValueVisitor<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>>: Sized {
     }
     /// Visits the given value as a union. No automatic recursion can happen here.
     #[inline(always)]
-    fn visit_union(&mut self, _v: &Self::V, _fields: NonZeroUsize) -> InterpResult<'tcx> {
+    fn visit_union(&mut self, _v: &Self::V, _fields: NonZero<usize>) -> InterpResult<'tcx> {
         Ok(())
     }
     /// Visits the given value as the pointer of a `Box`. There is nothing to recurse into.

compiler/rustc_const_eval/src/lib.rs

@@ -11,6 +11,7 @@ Rust MIR: a lowered representation of Rust.
 #![feature(assert_matches)]
 #![feature(box_patterns)]
 #![feature(decl_macro)]
+#![feature(generic_nonzero)]
 #![feature(let_chains)]
 #![feature(slice_ptr_get)]
 #![feature(never_type)]