bjoernager/rust
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Rollup merge of #127017 - mu001999-contrib:dead/enhance, r=pnkfelix

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Extend rules of dead code analysis for impls for adts to impls for types refer to adts

The rules of dead code analysis for impl blocks can be extended to self types which refer to adts.

So that we can lint the following unused struct and trait:
```rust
struct Foo; //~ ERROR struct `Foo` is never constructed

trait Trait { //~ ERROR trait `Trait` is never used
    fn foo(&self) {}
}

impl Trait for &Foo {}
```

r? `@pnkfelix`
This commit is contained in:
Trevor Gross 2024-07-26 02:20:29 -04:00 • committed by GitHub
commit a70dc297a8
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3 changed files with 87 additions and 10 deletions
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32
compiler/rustc_passes/src/dead.rs
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@ -54,7 +54,24 @@ impl Publicness {
}
}
fn struct_all_fields_are_public(tcx: TyCtxt<'_>, id: DefId) -> bool {
fn adt_of<'tcx>(ty: &hir::Ty<'tcx>) -> Option<(LocalDefId, DefKind)> {
match ty.kind {
TyKind::Path(hir::QPath::Resolved(_, path)) => {
if let Res::Def(def_kind, def_id) = path.res
&& let Some(local_def_id) = def_id.as_local()
{
Some((local_def_id, def_kind))
} else {
None
}
}
TyKind::Slice(ty) | TyKind::Array(ty, _) => adt_of(ty),
TyKind::Ptr(ty) | TyKind::Ref(_, ty) => adt_of(ty.ty),
_ => None,
}
}
fn struct_all_fields_are_public(tcx: TyCtxt<'_>, id: LocalDefId) -> bool {
// treat PhantomData and positional ZST as public,
// we don't want to lint types which only have them,
// cause it's a common way to use such types to check things like well-formedness
@ -79,10 +96,7 @@ fn struct_all_fields_are_public(tcx: TyCtxt<'_>, id: DefId) -> bool {
/// for enum and union, just check they are public,
/// and doesn't solve types like &T for now, just skip them
fn ty_ref_to_pub_struct(tcx: TyCtxt<'_>, ty: &hir::Ty<'_>) -> Publicness {
if let TyKind::Path(hir::QPath::Resolved(_, path)) = ty.kind
&& let Res::Def(def_kind, def_id) = path.res
&& def_id.is_local()
{
if let Some((def_id, def_kind)) = adt_of(ty) {
return match def_kind {
DefKind::Enum | DefKind::Union => {
let ty_is_public = tcx.visibility(def_id).is_public();
@ -565,10 +579,8 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
}
fn impl_item_with_used_self(&mut self, impl_id: hir::ItemId, impl_item_id: LocalDefId) -> bool {
if let TyKind::Path(hir::QPath::Resolved(_, path)) =
self.tcx.hir().item(impl_id).expect_impl().self_ty.kind
&& let Res::Def(def_kind, def_id) = path.res
&& let Some(local_def_id) = def_id.as_local()
if let Some((local_def_id, def_kind)) =
adt_of(self.tcx.hir().item(impl_id).expect_impl().self_ty)
&& matches!(def_kind, DefKind::Struct | DefKind::Enum | DefKind::Union)
{
if let Some(trait_item_id) = self.tcx.associated_item(impl_item_id).trait_item_def_id
@ -915,7 +927,7 @@ fn create_and_seed_worklist(
match tcx.def_kind(id) {
DefKind::Impl { .. } => false,
DefKind::AssocConst | DefKind::AssocTy | DefKind::AssocFn => !matches!(tcx.associated_item(id).container, AssocItemContainer::ImplContainer),
DefKind::Struct => struct_all_fields_are_public(tcx, id.to_def_id()) || has_allow_dead_code_or_lang_attr(tcx, id).is_some(),
DefKind::Struct => struct_all_fields_are_public(tcx, id) || has_allow_dead_code_or_lang_attr(tcx, id).is_some(),
_ => true
})
.map(|id| (id, ComesFromAllowExpect::No))