add test for rust-lang#106423

Fixes rust-lang#106423

tests/ui/const-generics/generic_const_exprs/poly-const-uneval-ice-106423.rs

@@ -0,0 +1,57 @@
+// issue: rust-lang/rust#106423
+// ICE collection encountered polymorphic constant: UnevaluatedConst {..}
+//@ edition:2021
+//@ check-pass
+
+#![feature(generic_const_exprs, generic_arg_infer)]
+#![allow(incomplete_features)]
+#![allow(unused)]
+
+use core::mem::MaybeUninit;
+
+pub struct Arr<T, const N: usize> {
+    v: [MaybeUninit<T>; N],
+}
+
+impl<T, const N: usize> Arr<T, N> {
+    const ELEM: MaybeUninit<T> = MaybeUninit::uninit();
+    const INIT: [MaybeUninit<T>; N] = [Self::ELEM; N]; // important for optimization of `new`
+
+    fn new() -> Self {
+        Arr { v: Self::INIT }
+    }
+}
+
+pub struct BaFormatFilter<const N: usize> {}
+
+pub enum DigitalFilter<const N: usize>
+where
+    [(); N * 2 + 1]: Sized,
+    [(); N * 2]: Sized,
+{
+    Ba(BaFormatFilter<{ N * 2 + 1 }>),
+}
+
+pub fn iirfilter_st_copy<const N: usize, const M: usize>(_: [f32; M]) -> DigitalFilter<N>
+where
+    [(); N * 2 + 1]: Sized,
+    [(); N * 2]: Sized,
+{
+    let zpk = zpk2tf_st(&Arr::<f32, { N * 2 }>::new(), &Arr::<f32, { N * 2 }>::new());
+    DigitalFilter::Ba(zpk)
+}
+
+pub fn zpk2tf_st<const N: usize>(
+    _z: &Arr<f32, N>,
+    _p: &Arr<f32, N>,
+) -> BaFormatFilter<{ N + 1 }>
+where
+    [(); N + 1]: Sized,
+{
+    BaFormatFilter {}
+}
+
+
+fn main() {
+    iirfilter_st_copy::<4, 2>([10., 50.,]);
+}