Add run-rustfix to unit_arg test

tests/ui/unit_arg.fixed

@@ -0,0 +1,53 @@
+// run-rustfix
+#![warn(clippy::unit_arg)]
+#![allow(clippy::no_effect, unused_must_use)]
+
+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 bad() {
+    foo(());
+    foo(());
+    foo(());
+    foo(());
+    foo3((), 2, 2);
+    let b = Bar;
+    b.bar(());
+}
+
+fn ok() {
+    foo(());
+    foo(1);
+    foo({ 1 });
+    foo3("a", 3, vec![3]);
+    let b = Bar;
+    b.bar({ 1 });
+    b.bar(());
+    question_mark();
+}
+
+fn question_mark() -> Result<(), ()> {
+    Ok(Ok(())?)?;
+    Ok(Ok(()))??;
+    Ok(())
+}
+
+fn main() {
+    bad();
+    ok();
+}

tests/ui/unit_arg.rs

@@ -1,5 +1,6 @@
+// run-rustfix
 #![warn(clippy::unit_arg)]
-#![allow(clippy::no_effect)]
+#![allow(clippy::no_effect, unused_must_use)]
 
 use std::fmt::Debug;
 

tests/ui/unit_arg.stderr

@@ -1,5 +1,5 @@
 error: passing a unit value to a function
-  --> $DIR/unit_arg.rs:23:9
+  --> $DIR/unit_arg.rs:24:9
    |
 LL |     foo({});
    |         ^^
@@ -11,7 +11,7 @@ LL |     foo(());
    |         ^^
 
 error: passing a unit value to a function
-  --> $DIR/unit_arg.rs:24:9
+  --> $DIR/unit_arg.rs:25:9
    |
 LL |       foo({
    |  _________^
@@ -24,7 +24,7 @@ LL |     foo(());
    |         ^^
 
 error: passing a unit value to a function
-  --> $DIR/unit_arg.rs:27:9
+  --> $DIR/unit_arg.rs:28:9
    |
 LL |     foo(foo(1));
    |         ^^^^^^
@@ -34,7 +34,7 @@ LL |     foo(());
    |         ^^
 
 error: passing a unit value to a function
-  --> $DIR/unit_arg.rs:28:9
+  --> $DIR/unit_arg.rs:29:9
    |
 LL |       foo({
    |  _________^
@@ -48,7 +48,7 @@ LL |     foo(());
    |         ^^
 
 error: passing a unit value to a function
-  --> $DIR/unit_arg.rs:32:10
+  --> $DIR/unit_arg.rs:33:10
    |
 LL |     foo3({}, 2, 2);
    |          ^^
@@ -58,7 +58,7 @@ LL |     foo3((), 2, 2);
    |          ^^
 
 error: passing a unit value to a function
-  --> $DIR/unit_arg.rs:34:11
+  --> $DIR/unit_arg.rs:35:11
    |
 LL |       b.bar({
    |  ___________^