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use crate::{LateContext, LateLintPass, LintContext};
use rustc_errors::DelayDm;
use rustc_hir as hir;
use rustc_middle::{traits::util::supertraits, ty};
use rustc_span::sym;
declare_lint! {
pub DEREF_INTO_DYN_SUPERTRAIT,
Warn,
"`Deref` implementation usage with a supertrait trait object for output might be shadowed in the future",
@future_incompatible = FutureIncompatibleInfo {
reference: "issue #89460 <https://github.com/rust-lang/rust/issues/89460>",
};
}
declare_lint_pass!(DerefIntoDynSupertrait => [DEREF_INTO_DYN_SUPERTRAIT]);
impl<'tcx> LateLintPass<'tcx> for DerefIntoDynSupertrait {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
if let hir::ItemKind::Impl(impl_) = item.kind
&& let Some(trait_) = &impl_.of_trait
&& let t = cx.tcx.type_of(item.owner_id)
&& let opt_did @ Some(did) = trait_.trait_def_id()
&& opt_did == cx.tcx.lang_items().deref_trait()
&& let ty::Dynamic(data, _, ty::Dyn) = t.kind()
&& let Some(t_principal) = data.principal()
&& let Some(target) = cx.get_associated_type(t, did, "Target")
&& let ty::Dynamic(data, _, ty::Dyn) = target.kind()
&& let Some(target_principal) = data.principal()
&& supertraits(cx.tcx, t_principal.with_self_ty(cx.tcx, cx.tcx.types.trait_object_dummy_self))
.any(|sup| sup.map_bound(|x| ty::ExistentialTraitRef::erase_self_ty(cx.tcx, x)) == target_principal)
{
cx.struct_span_lint(
DEREF_INTO_DYN_SUPERTRAIT,
cx.tcx.def_span(item.owner_id.def_id),
DelayDm(|| {
format!(
"`{t}` implements `Deref` with supertrait `{target_principal}` as target"
)
}),
|lint| {
if let Some(target_span) = impl_.items.iter().find_map(|i| (i.ident.name == sym::Target).then_some(i.span)) {
lint.span_label(target_span, "target type is set here");
}
lint
},
)
}
}
}