1 files changed, 22 insertions, 0 deletions
diff --git a/src/tools/clippy/tests/ui/unnecessary_first_then_check.rs b/src/tools/clippy/tests/ui/unnecessary_first_then_check.rs
new file mode 100644
index 00000000000..762b9599928
--- /dev/null
+++ b/src/tools/clippy/tests/ui/unnecessary_first_then_check.rs
@@ -0,0 +1,22 @@
+#![warn(clippy::unnecessary_first_then_check)]
+#![allow(clippy::useless_vec, clippy::const_is_empty)]
+
+fn main() {
+    let s = [1, 2, 3];
+    let _: bool = s.first().is_some();
+    let _: bool = s.first().is_none();
+
+    let v = vec![1, 2, 3];
+    let _: bool = v.first().is_some();
+
+    let n = [[1, 2, 3], [4, 5, 6]];
+    let _: bool = n[0].first().is_some();
+    let _: bool = n[0].first().is_none();
+
+    struct Foo {
+        bar: &'static [i32],
+    }
+    let f = [Foo { bar: &[] }];
+    let _: bool = f[0].bar.first().is_some();
+    let _: bool = f[0].bar.first().is_none();
+}