1 files changed, 147 insertions, 0 deletions
diff --git a/src/tools/clippy/tests/ui/manual_split_once.rs b/src/tools/clippy/tests/ui/manual_split_once.rs
new file mode 100644
index 000000000..ee2848a25
--- /dev/null
+++ b/src/tools/clippy/tests/ui/manual_split_once.rs
@@ -0,0 +1,147 @@
+// run-rustfix
+
+#![feature(custom_inner_attributes)]
+#![warn(clippy::manual_split_once)]
+#![allow(unused, clippy::iter_skip_next, clippy::iter_nth_zero)]
+
+extern crate itertools;
+
+#[allow(unused_imports)]
+use itertools::Itertools;
+
+fn main() {
+    let _ = "key=value".splitn(2, '=').nth(2);
+    let _ = "key=value".splitn(2, '=').nth(1).unwrap();
+    let _ = "key=value".splitn(2, '=').skip(1).next().unwrap();
+    let (_, _) = "key=value".splitn(2, '=').next_tuple().unwrap();
+
+    let s = String::from("key=value");
+    let _ = s.splitn(2, '=').nth(1).unwrap();
+
+    let s = Box::<str>::from("key=value");
+    let _ = s.splitn(2, '=').nth(1).unwrap();
+
+    let s = &"key=value";
+    let _ = s.splitn(2, '=').skip(1).next().unwrap();
+
+    fn _f(s: &str) -> Option<&str> {
+        let _ = s.splitn(2, '=').nth(1)?;
+        let _ = s.splitn(2, '=').skip(1).next()?;
+        let _ = s.rsplitn(2, '=').nth(1)?;
+        let _ = s.rsplitn(2, '=').skip(1).next()?;
+        None
+    }
+
+    // Don't lint, slices don't have `split_once`
+    let _ = [0, 1, 2].splitn(2, |&x| x == 1).nth(1).unwrap();
+
+    // `rsplitn` gives the results in the reverse order of `rsplit_once`
+    let _ = "key=value".rsplitn(2, '=').nth(1).unwrap();
+    let (_, _) = "key=value".rsplitn(2, '=').next_tuple().unwrap();
+    let _ = s.rsplitn(2, '=').nth(1);
+}
+
+fn indirect() -> Option<()> {
+    let mut iter = "a.b.c".splitn(2, '.');
+    let l = iter.next().unwrap();
+    let r = iter.next().unwrap();
+
+    let mut iter = "a.b.c".splitn(2, '.');
+    let l = iter.next()?;
+    let r = iter.next()?;
+
+    let mut iter = "a.b.c".rsplitn(2, '.');
+    let r = iter.next().unwrap();
+    let l = iter.next().unwrap();
+
+    let mut iter = "a.b.c".rsplitn(2, '.');
+    let r = iter.next()?;
+    let l = iter.next()?;
+
+    // could lint, currently doesn't
+
+    let mut iter = "a.b.c".splitn(2, '.');
+    let other = 1;
+    let l = iter.next()?;
+    let r = iter.next()?;
+
+    let mut iter = "a.b.c".splitn(2, '.');
+    let mut mut_binding = iter.next()?;
+    let r = iter.next()?;
+
+    let mut iter = "a.b.c".splitn(2, '.');
+    let tuple = (iter.next()?, iter.next()?);
+
+    // should not lint
+
+    let mut missing_unwrap = "a.b.c".splitn(2, '.');
+    let l = missing_unwrap.next();
+    let r = missing_unwrap.next();
+
+    let mut mixed_unrap = "a.b.c".splitn(2, '.');
+    let unwrap = mixed_unrap.next().unwrap();
+    let question_mark = mixed_unrap.next()?;
+
+    let mut iter = "a.b.c".splitn(2, '.');
+    let same_name = iter.next()?;
+    let same_name = iter.next()?;
+
+    let mut iter = "a.b.c".splitn(2, '.');
+    let shadows_existing = "d";
+    let shadows_existing = iter.next()?;
+    let r = iter.next()?;
+
+    let mut iter = "a.b.c".splitn(2, '.');
+    let becomes_shadowed = iter.next()?;
+    let becomes_shadowed = "d";
+    let r = iter.next()?;
+
+    let mut iter = "a.b.c".splitn(2, '.');
+    let l = iter.next()?;
+    let r = iter.next()?;
+    let third_usage = iter.next()?;
+
+    let mut n_three = "a.b.c".splitn(3, '.');
+    let l = n_three.next()?;
+    let r = n_three.next()?;
+
+    let mut iter = "a.b.c".splitn(2, '.');
+    {
+        let in_block = iter.next()?;
+    }
+    let r = iter.next()?;
+
+    let mut lacks_binding = "a.b.c".splitn(2, '.');
+    let _ = lacks_binding.next()?;
+    let r = lacks_binding.next()?;
+
+    let mut mapped = "a.b.c".splitn(2, '.').map(|_| "~");
+    let l = iter.next()?;
+    let r = iter.next()?;
+
+    let mut assigned = "";
+    let mut iter = "a.b.c".splitn(2, '.');
+    let l = iter.next()?;
+    assigned = iter.next()?;
+
+    None
+}
+
+fn _msrv_1_51() {
+    #![clippy::msrv = "1.51"]
+    // `str::split_once` was stabilized in 1.52. Do not lint this
+    let _ = "key=value".splitn(2, '=').nth(1).unwrap();
+
+    let mut iter = "a.b.c".splitn(2, '.');
+    let a = iter.next().unwrap();
+    let b = iter.next().unwrap();
+}
+
+fn _msrv_1_52() {
+    #![clippy::msrv = "1.52"]
+    let _ = "key=value".splitn(2, '=').nth(1).unwrap();
+
+    let mut iter = "a.b.c".splitn(2, '.');
+    let a = iter.next().unwrap();
+    let b = iter.next().unwrap();
+}