1 files changed, 95 insertions, 0 deletions
diff --git a/src/tools/clippy/tests/ui/let_underscore_must_use.rs b/src/tools/clippy/tests/ui/let_underscore_must_use.rs
new file mode 100644
index 000000000..1edb77c74
--- /dev/null
+++ b/src/tools/clippy/tests/ui/let_underscore_must_use.rs
@@ -0,0 +1,95 @@
+#![warn(clippy::let_underscore_must_use)]
+#![allow(clippy::unnecessary_wraps)]
+
+// Debug implementations can fire this lint,
+// so we shouldn't lint external macros
+#[derive(Debug)]
+struct Foo {
+    field: i32,
+}
+
+#[must_use]
+fn f() -> u32 {
+    0
+}
+
+fn g() -> Result<u32, u32> {
+    Ok(0)
+}
+
+#[must_use]
+fn l<T>(x: T) -> T {
+    x
+}
+
+fn h() -> u32 {
+    0
+}
+
+struct S;
+
+impl S {
+    #[must_use]
+    pub fn f(&self) -> u32 {
+        0
+    }
+
+    pub fn g(&self) -> Result<u32, u32> {
+        Ok(0)
+    }
+
+    fn k(&self) -> u32 {
+        0
+    }
+
+    #[must_use]
+    fn h() -> u32 {
+        0
+    }
+
+    fn p() -> Result<u32, u32> {
+        Ok(0)
+    }
+}
+
+trait Trait {
+    #[must_use]
+    fn a() -> u32;
+}
+
+impl Trait for S {
+    fn a() -> u32 {
+        0
+    }
+}
+
+fn main() {
+    let _ = f();
+    let _ = g();
+    let _ = h();
+    let _ = l(0_u32);
+
+    let s = S {};
+
+    let _ = s.f();
+    let _ = s.g();
+    let _ = s.k();
+
+    let _ = S::h();
+    let _ = S::p();
+
+    let _ = S::a();
+
+    let _ = if true { Ok(()) } else { Err(()) };
+
+    let a = Result::<(), ()>::Ok(());
+
+    let _ = a.is_ok();
+
+    let _ = a.map(|_| ());
+
+    let _ = a;
+
+    #[allow(clippy::let_underscore_must_use)]
+    let _ = a;
+}