clean-up

clippy_lints/src/unit_types/let_unit_value.rs

@@ -89,15 +89,30 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, format_args: &FormatArgsStorag
                         walk_body(&mut visitor, body);
 
                         let mut has_in_format_capture = false;
-                        suggestions.extend(visitor.spans.iter().filter_map(|span| match span {
+                        suggestions.extend(visitor.spans.into_iter().filter_map(|span| match span {
                             MaybeInFormatCapture::Yes => {
                                 has_in_format_capture = true;
                                 None
                             },
-                            MaybeInFormatCapture::No(span) => Some((*span, "()".to_string())),
+                            MaybeInFormatCapture::No(span) => Some((span, "()".to_string())),
                         }));
 
                         if has_in_format_capture {
+                            // In a case like this:
+                            // ```
+                            // let unit = returns_unit();
+                            // eprintln!("{unit}");
+                            // ```
+                            // we can't remove the `unit` binding and replace its uses with a `()`,
+                            // because the `eprintln!` would break.
+                            //
+                            // So do the following instead:
+                            // ```
+                            // let unit = ();
+                            // returns_unit();
+                            // eprintln!("{unit}");
+                            // ```
+                            // TODO: find a less awkward way to do this
                             suggestions.push((
                                 init.span,
                                 format!("();\n{}", reindent_multiline(&snip, false, indent_of(cx, local.span))),
@@ -132,6 +147,12 @@ struct UnitVariableCollector<'a, 'tcx> {
     macro_call: Option<&'a FormatArgs>,
 }
 
+/// Whether the unit variable is captured in a `format!`:
+///
+/// ```ignore
+/// let unit = ();
+/// eprintln!("{unit}");
+/// ```
 enum MaybeInFormatCapture {
     Yes,
     No(Span),

tests/ui/let_unit.fixed

@@ -1,5 +1,5 @@
 #![warn(clippy::let_unit_value)]
-#![allow(unused, clippy::no_effect, clippy::needless_late_init, path_statements)]
+#![allow(clippy::no_effect, clippy::needless_late_init, path_statements)]
 
 macro_rules! let_and_return {
     ($n:expr) => {{
@@ -15,12 +15,12 @@ fn main() {
     if true {
         // do not lint this, since () is explicit
         let _a = ();
-        let () = dummy();
+        let () = returns_unit();
         let () = ();
-        () = dummy();
+        () = returns_unit();
         () = ();
         let _a: () = ();
-        let _a: () = dummy();
+        let _a: () = returns_unit();
     }
 
     consume_units_with_for_loop(); // should be fine as well
@@ -30,7 +30,7 @@ fn main() {
     let_and_return!(()) // should be fine
 }
 
-fn dummy() {}
+fn returns_unit() {}
 
 // Related to issue #1964
 fn consume_units_with_for_loop() {
@@ -181,8 +181,6 @@ async fn issue10433() {
 pub async fn issue11502(a: ()) {}
 
 pub fn issue12594() {
-    fn returns_unit() {}
-
     fn returns_result<T>(res: T) -> Result<T, ()> {
         Ok(res)
     }
@@ -200,11 +198,10 @@ pub fn issue12594() {
 }
 
 fn issue15061() {
-    fn return_unit() {}
     fn do_something(x: ()) {}
 
     let res = ();
-    return_unit();
+    returns_unit();
     //~^ let_unit_value
     do_something(());
     println!("{res:?}");

tests/ui/let_unit.rs

@@ -1,5 +1,5 @@
 #![warn(clippy::let_unit_value)]
-#![allow(unused, clippy::no_effect, clippy::needless_late_init, path_statements)]
+#![allow(clippy::no_effect, clippy::needless_late_init, path_statements)]
 
 macro_rules! let_and_return {
     ($n:expr) => {{
@@ -15,12 +15,12 @@ fn main() {
     if true {
         // do not lint this, since () is explicit
         let _a = ();
-        let () = dummy();
+        let () = returns_unit();
         let () = ();
-        () = dummy();
+        () = returns_unit();
         () = ();
         let _a: () = ();
-        let _a: () = dummy();
+        let _a: () = returns_unit();
     }
 
     consume_units_with_for_loop(); // should be fine as well
@@ -30,7 +30,7 @@ fn main() {
     let_and_return!(()) // should be fine
 }
 
-fn dummy() {}
+fn returns_unit() {}
 
 // Related to issue #1964
 fn consume_units_with_for_loop() {
@@ -181,8 +181,6 @@ async fn issue10433() {
 pub async fn issue11502(a: ()) {}
 
 pub fn issue12594() {
-    fn returns_unit() {}
-
     fn returns_result<T>(res: T) -> Result<T, ()> {
         Ok(res)
     }
@@ -200,10 +198,9 @@ pub fn issue12594() {
 }
 
 fn issue15061() {
-    fn return_unit() {}
     fn do_something(x: ()) {}
 
-    let res = return_unit();
+    let res = returns_unit();
     //~^ let_unit_value
     do_something(res);
     println!("{res:?}");

tests/ui/let_unit.stderr

@@ -55,7 +55,7 @@ LL +     };
    |
 
 error: this let-binding has unit value
-  --> tests/ui/let_unit.rs:192:9
+  --> tests/ui/let_unit.rs:190:9
    |
 LL |         let res = returns_unit();
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -69,15 +69,15 @@ LL ~         returns_result(()).unwrap();
    |
 
 error: this let-binding has unit value
-  --> tests/ui/let_unit.rs:206:5
+  --> tests/ui/let_unit.rs:203:5
    |
-LL |     let res = return_unit();
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     let res = returns_unit();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 help: replace variable usages with `()`
    |
 LL ~     let res = ();
-LL ~     return_unit();
+LL ~     returns_unit();
 LL |
 LL ~     do_something(());
    |