2 use rustc_hir::def_id::DefId;
3 use rustc_middle::hir::map::blocks::FnLikeNode;
4 use rustc_middle::ty::query::Providers;
5 use rustc_middle::ty::TyCtxt;
6 use rustc_span::symbol::Symbol;
7 use rustc_target::spec::abi::Abi;
9 /// Whether the `def_id` is an unstable const fn and what feature gate is necessary to enable it
10 pub fn is_unstable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> Option<Symbol> {
11 if tcx.is_const_fn_raw(def_id) {
12 let const_stab = tcx.lookup_const_stability(def_id)?;
13 if const_stab.level.is_unstable() { Some(const_stab.feature) } else { None }
19 pub fn is_parent_const_impl_raw(tcx: TyCtxt<'_>, hir_id: hir::HirId) -> bool {
20 let parent_id = tcx.hir().get_parent_node(hir_id);
22 tcx.hir().get(parent_id),
23 hir::Node::Item(hir::Item {
24 kind: hir::ItemKind::Impl(hir::Impl { constness: hir::Constness::Const, .. }),
30 /// Checks whether the function has a `const` modifier or, in case it is an intrinsic, whether
31 /// said intrinsic has a `rustc_const_{un,}stable` attribute.
32 fn is_const_fn_raw(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
33 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
35 let node = tcx.hir().get(hir_id);
37 if let hir::Node::ForeignItem(hir::ForeignItem { kind: hir::ForeignItemKind::Fn(..), .. }) =
40 // Intrinsics use `rustc_const_{un,}stable` attributes to indicate constness. All other
41 // foreign items cannot be evaluated at compile-time.
42 if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = tcx.hir().get_foreign_abi(hir_id) {
43 tcx.lookup_const_stability(def_id).is_some()
47 } else if let Some(fn_like) = FnLikeNode::from_node(node) {
48 if fn_like.constness() == hir::Constness::Const {
52 // If the function itself is not annotated with `const`, it may still be a `const fn`
53 // if it resides in a const trait impl.
54 is_parent_const_impl_raw(tcx, hir_id)
55 } else if let hir::Node::Ctor(_) = node {
62 fn is_promotable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
63 tcx.is_const_fn(def_id)
64 && match tcx.lookup_const_stability(def_id) {
66 if cfg!(debug_assertions) && stab.promotable {
67 let sig = tcx.fn_sig(def_id);
70 hir::Unsafety::Normal,
71 "don't mark const unsafe fns as promotable",
72 // https://github.com/rust-lang/rust/pull/53851#issuecomment-418760682
81 pub fn provide(providers: &mut Providers) {
82 *providers = Providers { is_const_fn_raw, is_promotable_const_fn, ..*providers };