Add msrv tests

Author: Centri3

tests/ui/manual_try_fold.rs

@@ -82,3 +82,19 @@ fn main() {
         [1, 2, 3].iter().try_fold(0i32, |sum, i| sum.checked_add(*i)).unwrap();
     }
 }
+
+#[clippy::msrv = "1.26.0"]
+fn msrv_too_low() {
+    [1, 2, 3]
+        .iter()
+        .fold(Some(0i32), |sum, i| sum?.checked_add(*i))
+        .unwrap();
+}
+
+#[clippy::msrv = "1.27.0"]
+fn msrv_juust_right() {
+    [1, 2, 3]
+        .iter()
+        .fold(Some(0i32), |sum, i| sum?.checked_add(*i))
+        .unwrap();
+}

tests/ui/manual_try_fold.stderr

@@ -18,5 +18,11 @@ error: you seem to be using `Iterator::fold` on a type that implements `Try`
 LL |         .fold(NotOptionButWorse(0i32), |sum, i| NotOptionButWorse(0i32));
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `try_fold` instead: `try_fold(0i32, |sum, i|, ...)`
 
-error: aborting due to 3 previous errors
+error: you seem to be using `Iterator::fold` on a type that implements `Try`
+  --> $DIR/manual_try_fold.rs:98:10
+   |
+LL |         .fold(Some(0i32), |sum, i| sum?.checked_add(*i))
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `try_fold` instead: `try_fold(0i32, |sum, i|, ...)`
+
+error: aborting due to 4 previous errors