add regression test for rust-lang#74255

Author: lcnr

src/test/ui/const-generics/issues/issue-74255.rs

@@ -0,0 +1,18 @@
+// check-pass
+#![feature(const_generics)]
+#![allow(dead_code, incomplete_features)]
+
+#[derive(PartialEq, Eq)]
+enum IceEnum {
+    Variant
+}
+
+struct IceStruct;
+
+impl IceStruct {
+    fn ice_struct_fn<const I: IceEnum>() {}
+}
+
+fn main() {
+    IceStruct::ice_struct_fn::<{IceEnum::Variant}>();
+}