Auto merge of #9082 - Alexendoo:let_unit_allow, r=xFrednet

Fix direct `#[allow]` attributes in `let_unit_value`

Fixes part of #9080

Not sure why it doesn't work when the lint is emitted at the statement, but switching it to the local works fine

changelog: Fix direct `#[allow]` attributes in [`let_unit_value`]

clippy_lints/src/unit_types/let_unit_value.rs

@@ -4,18 +4,17 @@
 use core::ops::ControlFlow;
 use rustc_errors::Applicability;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::{Expr, ExprKind, PatKind, Stmt, StmtKind};
+use rustc_hir::{Expr, ExprKind, Local, PatKind};
 use rustc_lint::{LateContext, LintContext};
 use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::{self, Ty, TypeFoldable, TypeSuperFoldable, TypeVisitor};
 
 use super::LET_UNIT_VALUE;
 
-pub(super) fn check(cx: &LateContext<'_>, stmt: &Stmt<'_>) {
-    if let StmtKind::Local(local) = stmt.kind
-        && let Some(init) = local.init
+pub(super) fn check(cx: &LateContext<'_>, local: &Local<'_>) {
+    if let Some(init) = local.init
         && !local.pat.span.from_expansion()
-        && !in_external_macro(cx.sess(), stmt.span)
+        && !in_external_macro(cx.sess(), local.span)
         && cx.typeck_results().pat_ty(local.pat).is_unit()
     {
         let needs_inferred = for_each_value_source(init, &mut |e| if needs_inferred_result_ty(cx, e) {
@@ -29,7 +28,7 @@ pub(super) fn check(cx: &LateContext<'_>, stmt: &Stmt<'_>) {
                 span_lint_and_then(
                     cx,
                     LET_UNIT_VALUE,
-                    stmt.span,
+                    local.span,
                     "this let-binding has unit value",
                     |diag| {
                             diag.span_suggestion(
@@ -45,15 +44,15 @@ pub(super) fn check(cx: &LateContext<'_>, stmt: &Stmt<'_>) {
             span_lint_and_then(
                 cx,
                 LET_UNIT_VALUE,
-                stmt.span,
+                local.span,
                 "this let-binding has unit value",
                 |diag| {
                     if let Some(expr) = &local.init {
                         let snip = snippet_with_macro_callsite(cx, expr.span, "()");
                         diag.span_suggestion(
-                            stmt.span,
+                            local.span,
                             "omit the `let` binding",
-                            format!("{};", snip),
+                            format!("{snip};"),
                             Applicability::MachineApplicable, // snippet
                         );
                     }

clippy_lints/src/unit_types/mod.rs

@@ -3,7 +3,7 @@
 mod unit_cmp;
 mod utils;
 
-use rustc_hir::{Expr, Stmt};
+use rustc_hir::{Expr, Local};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
@@ -99,8 +99,8 @@
 declare_lint_pass!(UnitTypes => [LET_UNIT_VALUE, UNIT_CMP, UNIT_ARG]);
 
 impl LateLintPass<'_> for UnitTypes {
-    fn check_stmt(&mut self, cx: &LateContext<'_>, stmt: &Stmt<'_>) {
-        let_unit_value::check(cx, stmt);
+    fn check_local(&mut self, cx: &LateContext<'_>, local: &Local<'_>) {
+        let_unit_value::check(cx, local);
     }
 
     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {

tests/ui/let_unit.fixed

@@ -1,8 +1,9 @@
 // run-rustfix
 
+#![feature(lint_reasons)]
 #![warn(clippy::let_unit_value)]
 #![allow(clippy::no_effect)]
-#![allow(unused_variables)]
+#![allow(unused)]
 
 macro_rules! let_and_return {
     ($n:expr) => {{
@@ -113,3 +114,12 @@ fn _returns_generic() {
         Some(_) => (),
     };
 }
+
+fn attributes() {
+    fn f() {}
+
+    #[allow(clippy::let_unit_value)]
+    let _ = f();
+    #[expect(clippy::let_unit_value)]
+    let _ = f();
+}

tests/ui/let_unit.rs

@@ -1,8 +1,9 @@
 // run-rustfix
 
+#![feature(lint_reasons)]
 #![warn(clippy::let_unit_value)]
 #![allow(clippy::no_effect)]
-#![allow(unused_variables)]
+#![allow(unused)]
 
 macro_rules! let_and_return {
     ($n:expr) => {{
@@ -113,3 +114,12 @@ fn f4<T>(mut x: Vec<T>) -> T {
         Some(_) => (),
     };
 }
+
+fn attributes() {
+    fn f() {}
+
+    #[allow(clippy::let_unit_value)]
+    let _ = f();
+    #[expect(clippy::let_unit_value)]
+    let _ = f();
+}

tests/ui/let_unit.stderr

@@ -1,5 +1,5 @@
 error: this let-binding has unit value
-  --> $DIR/let_unit.rs:14:5
+  --> $DIR/let_unit.rs:15:5
    |
 LL |     let _x = println!("x");
    |     ^^^^^^^^^^^^^^^^^^^^^^^ help: omit the `let` binding: `println!("x");`
@@ -7,13 +7,13 @@ LL |     let _x = println!("x");
    = note: `-D clippy::let-unit-value` implied by `-D warnings`
 
 error: this let-binding has unit value
-  --> $DIR/let_unit.rs:18:9
+  --> $DIR/let_unit.rs:19:9
    |
 LL |         let _a = ();
    |         ^^^^^^^^^^^^ help: omit the `let` binding: `();`
 
 error: this let-binding has unit value
-  --> $DIR/let_unit.rs:53:5
+  --> $DIR/let_unit.rs:54:5
    |
 LL | /     let _ = v
 LL | |         .into_iter()
@@ -36,7 +36,7 @@ LL +         .unwrap();
    |
 
 error: this let-binding has unit value
-  --> $DIR/let_unit.rs:80:5
+  --> $DIR/let_unit.rs:81:5
    |
 LL |     let x: () = f(); // Lint.
    |     ^^^^-^^^^^^^^^^^
@@ -44,7 +44,7 @@ LL |     let x: () = f(); // Lint.
    |         help: use a wild (`_`) binding: `_`
 
 error: this let-binding has unit value
-  --> $DIR/let_unit.rs:83:5
+  --> $DIR/let_unit.rs:84:5
    |
 LL |     let x: () = f2(0i32); // Lint.
    |     ^^^^-^^^^^^^^^^^^^^^^
@@ -52,31 +52,31 @@ LL |     let x: () = f2(0i32); // Lint.
    |         help: use a wild (`_`) binding: `_`
 
 error: this let-binding has unit value
-  --> $DIR/let_unit.rs:85:5
+  --> $DIR/let_unit.rs:86:5
    |
 LL |     let _: () = f3(()); // Lint
    |     ^^^^^^^^^^^^^^^^^^^ help: omit the `let` binding: `f3(());`
 
 error: this let-binding has unit value
-  --> $DIR/let_unit.rs:86:5
+  --> $DIR/let_unit.rs:87:5
    |
 LL |     let x: () = f3(()); // Lint
    |     ^^^^^^^^^^^^^^^^^^^ help: omit the `let` binding: `f3(());`
 
 error: this let-binding has unit value
-  --> $DIR/let_unit.rs:88:5
+  --> $DIR/let_unit.rs:89:5
    |
 LL |     let _: () = f4(vec![()]); // Lint
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^ help: omit the `let` binding: `f4(vec![()]);`
 
 error: this let-binding has unit value
-  --> $DIR/let_unit.rs:89:5
+  --> $DIR/let_unit.rs:90:5
    |
 LL |     let x: () = f4(vec![()]); // Lint
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^ help: omit the `let` binding: `f4(vec![()]);`
 
 error: this let-binding has unit value
-  --> $DIR/let_unit.rs:98:5
+  --> $DIR/let_unit.rs:99:5
    |
 LL |     let x: () = if true { f() } else { f2(0) }; // Lint
    |     ^^^^-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -84,7 +84,7 @@ 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:109:5
+  --> $DIR/let_unit.rs:110:5
    |
 LL | /     let _: () = match Some(0) {
 LL | |         None => f2(1),