skip let _: ()

clippy_lints/src/unit_types/let_unit_value.rs

@@ -24,7 +24,12 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
         && cx.typeck_results().pat_ty(local.pat).is_unit()
     {
         // skip `let awa = ()`
-        if let ExprKind::Tup(elements) = init.kind && elements.is_empty() {
+        if let ExprKind::Tup([]) = init.kind {
+            return;
+        }
+
+        // skip `let _: () = { ... }`
+        if let Some(ty) = local.ty && let TyKind::Tup([]) = ty.kind {
             return;
         }
 
@@ -43,7 +48,7 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
                     |diag| {
                         diag.span_suggestion(
                             local.pat.span,
-                            "use a wild (`_`) binding",
+                            "use a wildcard binding",
                             "_",
                             Applicability::MaybeIncorrect, // snippet
                         );

tests/ui/let_unit.fixed

@@ -17,14 +17,14 @@ fn main() {
     if true {
         // do not lint this, since () is explicit
         let _a = ();
+        let () = dummy();
+        let () = ();
+        () = dummy();
+        () = ();
+        let _a: () = ();
+        let _a: () = dummy();
     }
 
-    // do not lint this, since () is explicit
-    let () = dummy();
-    let () = ();
-    () = dummy();
-    () = ();
-
     consume_units_with_for_loop(); // should be fine as well
 
     multiline_sugg();
@@ -86,13 +86,13 @@ fn _returns_generic() {
     }
 
     let _: () = f(); // Ok
-    let _: () = f(); // Lint.
+    let x: () = f(); // Lint.
 
     let _: () = f2(0i32); // Ok
-    let _: () = f2(0i32); // Lint.
+    let x: () = f2(0i32); // Lint.
 
-    f3(()); // Lint
-    f3(()); // Lint
+    let _: () = f3(()); // Lint
+    let x: () = f3(()); // Lint
 
     // Should lint:
     // fn f4<T>(mut x: Vec<T>) -> T {
@@ -108,7 +108,7 @@ fn _returns_generic() {
     };
 
     let _: () = if true { f() } else { f2(0) }; // Ok
-    let _: () = if true { f() } else { f2(0) }; // Lint
+    let x: () = if true { f() } else { f2(0) }; // Lint
 
     // Ok
     let _: () = match Some(0) {
@@ -119,7 +119,7 @@ fn _returns_generic() {
     };
 
     // Lint
-    match Some(0) {
+    let _: () = match Some(0) {
         None => f2(1),
         Some(0) => f(),
         Some(1) => f2(3),
@@ -166,7 +166,7 @@ fn _returns_generic() {
         {
             let _: () = x;
             let _: () = y;
-            z;
+            let _: () = z;
             let _: () = x1;
             let _: () = x2;
             let _: () = opt;

tests/ui/let_unit.rs

@@ -17,14 +17,14 @@ fn main() {
     if true {
         // do not lint this, since () is explicit
         let _a = ();
+        let () = dummy();
+        let () = ();
+        () = dummy();
+        () = ();
+        let _a: () = ();
+        let _a: () = dummy();
     }
 
-    // do not lint this, since () is explicit
-    let () = dummy();
-    let () = ();
-    () = dummy();
-    () = ();
-
     consume_units_with_for_loop(); // should be fine as well
 
     multiline_sugg();

tests/ui/let_unit.stderr

@@ -29,68 +29,5 @@ LL +         .next()
 LL +         .unwrap();
    |
 
-error: this let-binding has unit value
-  --> $DIR/let_unit.rs:89:5
-   |
-LL |     let x: () = f(); // Lint.
-   |     ^^^^-^^^^^^^^^^^
-   |         |
-   |         help: use a wild (`_`) binding: `_`
-
-error: this let-binding has unit value
-  --> $DIR/let_unit.rs:92:5
-   |
-LL |     let x: () = f2(0i32); // Lint.
-   |     ^^^^-^^^^^^^^^^^^^^^^
-   |         |
-   |         help: use a wild (`_`) binding: `_`
-
-error: this let-binding has unit value
-  --> $DIR/let_unit.rs:94:5
-   |
-LL |     let _: () = f3(()); // Lint
-   |     ^^^^^^^^^^^^^^^^^^^ help: omit the `let` binding: `f3(());`
-
-error: this let-binding has unit value
-  --> $DIR/let_unit.rs:95:5
-   |
-LL |     let x: () = f3(()); // Lint
-   |     ^^^^^^^^^^^^^^^^^^^ help: omit the `let` binding: `f3(());`
-
-error: this let-binding has unit value
-  --> $DIR/let_unit.rs:111:5
-   |
-LL |     let x: () = if true { f() } else { f2(0) }; // Lint
-   |     ^^^^-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |         |
-   |         help: use a wild (`_`) binding: `_`
-
-error: this let-binding has unit value
-  --> $DIR/let_unit.rs:122:5
-   |
-LL | /     let _: () = match Some(0) {
-LL | |         None => f2(1),
-LL | |         Some(0) => f(),
-LL | |         Some(1) => f2(3),
-LL | |         Some(_) => (),
-LL | |     };
-   | |______^
-   |
-help: omit the `let` binding
-   |
-LL ~     match Some(0) {
-LL +         None => f2(1),
-LL +         Some(0) => f(),
-LL +         Some(1) => f2(3),
-LL +         Some(_) => (),
-LL +     };
-   |
-
-error: this let-binding has unit value
-  --> $DIR/let_unit.rs:169:13
-   |
-LL |             let _: () = z;
-   |             ^^^^^^^^^^^^^^ help: omit the `let` binding: `z;`
-
-error: aborting due to 9 previous errors
+error: aborting due to 2 previous errors