Add a test for #71202

Closes #71202

Author: osa1

src/test/ui/const-generics/issue-71202.rs

@@ -0,0 +1,33 @@
+// check-pass
+
+#![feature(const_generics)]
+#![allow(incomplete_features, const_evaluatable_unchecked)]
+
+use std::marker::PhantomData;
+
+struct DataHolder<T> {
+    item: T,
+}
+
+impl<T: Copy> DataHolder<T> {
+    const ITEM_IS_COPY: [(); 1 - {
+        trait NotCopy {
+            const VALUE: bool = false;
+        }
+
+        impl<__Type: ?Sized> NotCopy for __Type {}
+
+        struct IsCopy<__Type: ?Sized>(PhantomData<__Type>);
+
+        impl<__Type> IsCopy<__Type>
+        where
+            __Type: Sized + Copy,
+        {
+            const VALUE: bool = true;
+        }
+
+        <IsCopy<T>>::VALUE
+    } as usize] = [];
+}
+
+fn main() {}