[useless_conversion]: fix FP in macro and add test

tests/ui/crashes/ice-11065.rs

@@ -0,0 +1,19 @@
+#![warn(clippy::useless_conversion)]
+
+use std::iter::FromIterator;
+use std::option::IntoIter as OptionIter;
+
+fn eq<T: Eq>(a: T, b: T) -> bool {
+    a == b
+}
+
+macro_rules! tests {
+    ($($expr:expr, $ty:ty, ($($test:expr),*);)+) => (pub fn main() {$({
+        const C: $ty = $expr;
+        assert!(eq(C($($test),*), $expr($($test),*)));
+    })+})
+}
+
+tests! {
+    FromIterator::from_iter, fn(OptionIter<i32>) -> Vec<i32>, (Some(5).into_iter());
+}