1 files changed, 133 insertions, 0 deletions
diff --git a/src/tools/clippy/tests/ui/unit_arg.rs b/src/tools/clippy/tests/ui/unit_arg.rs
new file mode 100644
index 000000000..38be87bdd
--- /dev/null
+++ b/src/tools/clippy/tests/ui/unit_arg.rs
@@ -0,0 +1,133 @@
+#![warn(clippy::unit_arg)]
+#![allow(
+    clippy::no_effect,
+    unused_must_use,
+    unused_variables,
+    clippy::unused_unit,
+    clippy::unnecessary_wraps,
+    clippy::or_fun_call,
+    clippy::needless_question_mark,
+    clippy::self_named_constructors,
+    clippy::let_unit_value
+)]
+
+use std::fmt::Debug;
+
+fn foo<T: Debug>(t: T) {
+    println!("{:?}", t);
+}
+
+fn foo3<T1: Debug, T2: Debug, T3: Debug>(t1: T1, t2: T2, t3: T3) {
+    println!("{:?}, {:?}, {:?}", t1, t2, t3);
+}
+
+struct Bar;
+
+impl Bar {
+    fn bar<T: Debug>(&self, t: T) {
+        println!("{:?}", t);
+    }
+}
+
+fn baz<T: Debug>(t: T) {
+    foo(t);
+}
+
+trait Tr {
+    type Args;
+    fn do_it(args: Self::Args);
+}
+
+struct A;
+impl Tr for A {
+    type Args = ();
+    fn do_it(_: Self::Args) {}
+}
+
+struct B;
+impl Tr for B {
+    type Args = <A as Tr>::Args;
+
+    fn do_it(args: Self::Args) {
+        A::do_it(args)
+    }
+}
+
+fn bad() {
+    foo({
+        1;
+    });
+    foo(foo(1));
+    foo({
+        foo(1);
+        foo(2);
+    });
+    let b = Bar;
+    b.bar({
+        1;
+    });
+    taking_multiple_units(foo(0), foo(1));
+    taking_multiple_units(foo(0), {
+        foo(1);
+        foo(2);
+    });
+    taking_multiple_units(
+        {
+            foo(0);
+            foo(1);
+        },
+        {
+            foo(2);
+            foo(3);
+        },
+    );
+    // here Some(foo(2)) isn't the top level statement expression, wrap the suggestion in a block
+    None.or(Some(foo(2)));
+    // in this case, the suggestion can be inlined, no need for a surrounding block
+    // foo(()); foo(()) instead of { foo(()); foo(()) }
+    foo(foo(()));
+}
+
+fn ok() {
+    foo(());
+    foo(1);
+    foo({ 1 });
+    foo3("a", 3, vec![3]);
+    let b = Bar;
+    b.bar({ 1 });
+    b.bar(());
+    question_mark();
+    let named_unit_arg = ();
+    foo(named_unit_arg);
+    baz(());
+    B::do_it(());
+}
+
+fn question_mark() -> Result<(), ()> {
+    Ok(Ok(())?)?;
+    Ok(Ok(()))??;
+    Ok(())
+}
+
+#[allow(dead_code)]
+mod issue_2945 {
+    fn unit_fn() -> Result<(), i32> {
+        Ok(())
+    }
+
+    fn fallible() -> Result<(), i32> {
+        Ok(unit_fn()?)
+    }
+}
+
+#[allow(dead_code)]
+fn returning_expr() -> Option<()> {
+    Some(foo(1))
+}
+
+fn taking_multiple_units(a: (), b: ()) {}
+
+fn main() {
+    bad();
+    ok();
+}