1 files changed, 100 insertions, 0 deletions
diff --git a/src/tools/clippy/tests/ui/manual_try_fold.rs b/src/tools/clippy/tests/ui/manual_try_fold.rs
new file mode 100644
index 00000000000..4521e9fa1a5
--- /dev/null
+++ b/src/tools/clippy/tests/ui/manual_try_fold.rs
@@ -0,0 +1,100 @@
+//@aux-build:proc_macros.rs:proc-macro
+#![allow(clippy::unnecessary_fold, unused)]
+#![warn(clippy::manual_try_fold)]
+#![feature(try_trait_v2)]
+
+use std::ops::ControlFlow;
+use std::ops::FromResidual;
+use std::ops::Try;
+
+#[macro_use]
+extern crate proc_macros;
+
+// Test custom `Try` with more than 1 argument
+struct NotOption(i32, i32);
+
+impl<R> FromResidual<R> for NotOption {
+    fn from_residual(_: R) -> Self {
+        todo!()
+    }
+}
+
+impl Try for NotOption {
+    type Output = ();
+    type Residual = ();
+
+    fn from_output(_: Self::Output) -> Self {
+        todo!()
+    }
+
+    fn branch(self) -> ControlFlow<Self::Residual, Self::Output> {
+        todo!()
+    }
+}
+
+// Test custom `Try` with only 1 argument
+#[derive(Default)]
+struct NotOptionButWorse(i32);
+
+impl<R> FromResidual<R> for NotOptionButWorse {
+    fn from_residual(_: R) -> Self {
+        todo!()
+    }
+}
+
+impl Try for NotOptionButWorse {
+    type Output = ();
+    type Residual = ();
+
+    fn from_output(_: Self::Output) -> Self {
+        todo!()
+    }
+
+    fn branch(self) -> ControlFlow<Self::Residual, Self::Output> {
+        todo!()
+    }
+}
+
+fn main() {
+    [1, 2, 3]
+        .iter()
+        .fold(Some(0i32), |sum, i| sum?.checked_add(*i))
+        .unwrap();
+    [1, 2, 3]
+        .iter()
+        .fold(NotOption(0i32, 0i32), |sum, i| NotOption(0i32, 0i32));
+    [1, 2, 3]
+        .iter()
+        .fold(NotOptionButWorse(0i32), |sum, i| NotOptionButWorse(0i32));
+    // Do not lint
+    [1, 2, 3].iter().try_fold(0i32, |sum, i| sum.checked_add(*i)).unwrap();
+    [1, 2, 3].iter().fold(0i32, |sum, i| sum + i);
+    [1, 2, 3]
+        .iter()
+        .fold(NotOptionButWorse::default(), |sum, i| NotOptionButWorse::default());
+    external! {
+        [1, 2, 3].iter().fold(Some(0i32), |sum, i| sum?.checked_add(*i)).unwrap();
+        [1, 2, 3].iter().try_fold(0i32, |sum, i| sum.checked_add(*i)).unwrap();
+    }
+    with_span! {
+        span
+        [1, 2, 3].iter().fold(Some(0i32), |sum, i| sum?.checked_add(*i)).unwrap();
+        [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();
+}