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Lint on trait declarations, not implementations

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This commit is contained in:
Micha White 2023-02-26 12:11:47 -05:00
parent 022f76d432
commit 1b55c81db5
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GPG Key ID: AED94BFA1C301389
3 changed files with 94 additions and 51 deletions
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102
clippy_lints/src/unnecessary_box_returns.rs
View File

@ -1,9 +1,8 @@
use clippy_utils::diagnostics::span_lint_and_then;
use rustc_errors::Applicability;
use rustc_hir::{def_id::LocalDefId, intravisit::FnKind, Body, FnDecl, FnRetTy};
use rustc_hir::{def_id::LocalDefId, FnDecl, FnRetTy, ImplItemKind, Item, ItemKind, Node, TraitItem, TraitItemKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::Span;
declare_clippy_lint! {
/// ### What it does
@ -35,54 +34,63 @@
}
declare_lint_pass!(UnnecessaryBoxReturns => [UNNECESSARY_BOX_RETURNS]);
impl LateLintPass<'_> for UnnecessaryBoxReturns {
fn check_fn(
&mut self,
cx: &LateContext<'_>,
fn_kind: FnKind<'_>,
decl: &FnDecl<'_>,
_: &Body<'_>,
_: Span,
def_id: LocalDefId,
) {
// it's unclear what part of a closure you would span, so for now it's ignored
// if this is changed, please also make sure not to call `hir_ty_to_ty` below
if matches!(fn_kind, FnKind::Closure) {
return;
}
fn check_fn_decl(cx: &LateContext<'_>, decl: &FnDecl<'_>, def_id: LocalDefId) {
let FnRetTy::Return(return_ty_hir) = &decl.output else { return };
let FnRetTy::Return(return_ty_hir) = &decl.output else { return };
let return_ty = cx
.tcx
.erase_late_bound_regions(cx.tcx.fn_sig(def_id).skip_binder())
.output();
let return_ty = cx
.tcx
.erase_late_bound_regions(cx.tcx.fn_sig(def_id).skip_binder())
.output();
if !return_ty.is_box() {
return;
}
if !return_ty.is_box() {
return;
}
let boxed_ty = return_ty.boxed_ty();
let boxed_ty = return_ty.boxed_ty();
// it's sometimes useful to return Box<T> if T is unsized, so don't lint those
if boxed_ty.is_sized(cx.tcx, cx.param_env) {
span_lint_and_then(
cx,
UNNECESSARY_BOX_RETURNS,
return_ty_hir.span,
format!("boxed return of the sized type `{boxed_ty}`").as_str(),
|diagnostic| {
diagnostic.span_suggestion(
return_ty_hir.span,
"try",
boxed_ty.to_string(),
// the return value and function callers also needs to
// be changed, so this can't be MachineApplicable
Applicability::Unspecified,
);
diagnostic.help("changing this also requires a change to the return expressions in this function");
},
);
}
// it's sometimes useful to return Box<T> if T is unsized, so don't lint those
if boxed_ty.is_sized(cx.tcx, cx.param_env) {
span_lint_and_then(
cx,
UNNECESSARY_BOX_RETURNS,
return_ty_hir.span,
format!("boxed return of the sized type `{boxed_ty}`").as_str(),
|diagnostic| {
diagnostic.span_suggestion(
return_ty_hir.span,
"try",
boxed_ty.to_string(),
// the return value and function callers also needs to
// be changed, so this can't be MachineApplicable
Applicability::Unspecified,
);
diagnostic.help("changing this also requires a change to the return expressions in this function");
},
);
}
}
impl LateLintPass<'_> for UnnecessaryBoxReturns {
fn check_trait_item(&mut self, cx: &LateContext<'_>, item: &TraitItem<'_>) {
let TraitItemKind::Fn(signature, _) = &item.kind else { return };
check_fn_decl(cx, signature.decl, item.owner_id.def_id);
}
fn check_impl_item(&mut self, cx: &LateContext<'_>, item: &rustc_hir::ImplItem<'_>) {
// Ignore implementations of traits, because the lint should be on the
// trait, not on the implmentation of it.
let Node::Item(parent) = cx.tcx.hir().get_parent(item.hir_id()) else { return };
let ItemKind::Impl(parent) = parent.kind else { return };
if parent.of_trait.is_some() {
return;
}
let ImplItemKind::Fn(signature, ..) = &item.kind else { return };
check_fn_decl(cx, signature.decl, item.owner_id.def_id);
}
fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
let ItemKind::Fn(signature, ..) = &item.kind else { return };
check_fn_decl(cx, signature.decl, item.owner_id.def_id);
}
}

19
tests/ui/unnecessary_box_returns.rs
View File

@ -1,7 +1,26 @@
#![warn(clippy::unnecessary_box_returns)]
trait Bar {
// lint
fn baz(&self) -> Box<usize>;
}
struct Foo {}
impl Bar for Foo {
// don't lint: this is a problem with the trait, not the implementation
fn baz(&self) -> Box<usize> {
Box::new(42)
}
}
impl Foo {
fn baz(&self) -> Box<usize> {
// lint
Box::new(13)
}
}
// lint
fn boxed_usize() -> Box<usize> {
Box::new(5)

24
tests/ui/unnecessary_box_returns.stderr
View File

@ -1,19 +1,35 @@
error: boxed return of the sized type `usize`
--> $DIR/unnecessary_box_returns.rs:6:21
--> $DIR/unnecessary_box_returns.rs:5:22
|
LL | fn baz(&self) -> Box<usize>;
| ^^^^^^^^^^ help: try: `usize`
|
= help: changing this also requires a change to the return expressions in this function
= note: `-D clippy::unnecessary-box-returns` implied by `-D warnings`
error: boxed return of the sized type `usize`
--> $DIR/unnecessary_box_returns.rs:18:22
|
LL | fn baz(&self) -> Box<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 `usize`
--> $DIR/unnecessary_box_returns.rs:25:21
|
LL | fn boxed_usize() -> Box<usize> {
| ^^^^^^^^^^ help: try: `usize`
|
= help: changing this also requires a change to the return expressions in this function
= note: `-D clippy::unnecessary-box-returns` implied by `-D warnings`
error: boxed return of the sized type `Foo`
--> $DIR/unnecessary_box_returns.rs:11:19
--> $DIR/unnecessary_box_returns.rs:30:19
|
LL | fn boxed_foo() -> Box<Foo> {
| ^^^^^^^^ help: try: `Foo`
|
= help: changing this also requires a change to the return expressions in this function
error: aborting due to 2 previous errors
error: aborting due to 4 previous errors