Don't lint functions with "box" in their name

clippy_lints/src/unnecessary_box_returns.rs

@@ -3,6 +3,7 @@ use rustc_errors::Applicability;
 use rustc_hir::{def_id::LocalDefId, FnDecl, FnRetTy, ImplItemKind, Item, ItemKind, Node, TraitItem, TraitItemKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
+use rustc_span::Symbol;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -46,12 +47,17 @@ impl UnnecessaryBoxReturns {
         }
     }
 
-    fn check_fn_decl(&mut self, cx: &LateContext<'_>, decl: &FnDecl<'_>, def_id: LocalDefId) {
+    fn check_fn_item(&mut self, cx: &LateContext<'_>, decl: &FnDecl<'_>, def_id: LocalDefId, name: Symbol) {
         // we don't want to tell someone to break an exported function if they ask us not to
         if self.avoid_breaking_exported_api && cx.effective_visibilities.is_exported(def_id) {
             return;
         }
 
+        // functions which contain the word "box" are exempt from this lint
+        if name.as_str().contains("box") {
+            return;
+        }
+
         let FnRetTy::Return(return_ty_hir) = &decl.output else { return };
 
         let return_ty = cx
@@ -91,7 +97,7 @@ impl UnnecessaryBoxReturns {
 impl LateLintPass<'_> for UnnecessaryBoxReturns {
     fn check_trait_item(&mut self, cx: &LateContext<'_>, item: &TraitItem<'_>) {
         let TraitItemKind::Fn(signature, _) = &item.kind else { return };
-        self.check_fn_decl(cx, signature.decl, item.owner_id.def_id);
+        self.check_fn_item(cx, signature.decl, item.owner_id.def_id, item.ident.name);
     }
 
     fn check_impl_item(&mut self, cx: &LateContext<'_>, item: &rustc_hir::ImplItem<'_>) {
@@ -104,11 +110,11 @@ impl LateLintPass<'_> for UnnecessaryBoxReturns {
         }
 
         let ImplItemKind::Fn(signature, ..) = &item.kind else { return };
-        self.check_fn_decl(cx, signature.decl, item.owner_id.def_id);
+        self.check_fn_item(cx, signature.decl, item.owner_id.def_id, item.ident.name);
     }
 
     fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
         let ItemKind::Fn(signature, ..) = &item.kind else { return };
-        self.check_fn_decl(cx, signature.decl, item.owner_id.def_id);
+        self.check_fn_item(cx, signature.decl, item.owner_id.def_id, item.ident.name);
     }
 }

tests/ui/unnecessary_box_returns.rs

@@ -22,25 +22,30 @@ impl Foo {
 }
 
 // lint
-fn boxed_usize() -> Box<usize> {
+fn bxed_usize() -> Box<usize> {
     Box::new(5)
 }
 
 // lint
-fn _boxed_foo() -> Box<Foo> {
+fn _bxed_foo() -> Box<Foo> {
     Box::new(Foo {})
 }
 
 // don't lint: this is exported
-pub fn boxed_foo() -> Box<Foo> {
+pub fn bxed_foo() -> Box<Foo> {
     Box::new(Foo {})
 }
 
 // don't lint: str is unsized
-fn boxed_str() -> Box<str> {
+fn bxed_str() -> Box<str> {
     "Hello, world!".to_string().into_boxed_str()
 }
 
+// don't lint: function contains the word, "box"
+fn boxed_usize() -> Box<usize> {
+    Box::new(7)
+}
+
 // don't lint: this has an unspecified return type
 fn default() {}
 

tests/ui/unnecessary_box_returns.stderr

@@ -16,18 +16,18 @@ LL |     fn baz(&self) -> Box<usize> {
    = help: changing this also requires a change to the return expressions in this function
 
 error: boxed return of the sized type `usize`
-  --> $DIR/unnecessary_box_returns.rs:25:21
+  --> $DIR/unnecessary_box_returns.rs:25:20
    |
-LL | fn boxed_usize() -> Box<usize> {
+LL | fn bxed_usize() -> Box<usize> {
-   |                     ^^^^^^^^^^ help: try: `usize`
+   |                    ^^^^^^^^^^ help: try: `usize`
    |
    = help: changing this also requires a change to the return expressions in this function
 
 error: boxed return of the sized type `Foo`
-  --> $DIR/unnecessary_box_returns.rs:30:20
+  --> $DIR/unnecessary_box_returns.rs:30:19
    |
-LL | fn _boxed_foo() -> Box<Foo> {
+LL | fn _bxed_foo() -> Box<Foo> {
-   |                    ^^^^^^^^ help: try: `Foo`
+   |                   ^^^^^^^^ help: try: `Foo`
    |
    = help: changing this also requires a change to the return expressions in this function