Add regression test for rust-lang#58311

src/test/ui/dropck/dropck_fn_type.rs

@@ -0,0 +1,18 @@
+// run-pass
+//! Regression test for #58311, regarding the usage of Fn types in drop impls
+
+#[allow(dead_code)]
+struct S<F: Fn() -> [u8; 1]>(F);
+
+impl<F: Fn() -> [u8; 1]> Drop for S<F> {
+    fn drop(&mut self) {}
+}
+
+#[allow(dead_code)]
+struct P<A, F: FnOnce() -> [A; 10]>(F);
+
+impl<A, F: FnOnce() -> [A; 10]> Drop for P<A, F> {
+    fn drop(&mut self) {}
+}
+
+fn main() {}