rustc_const_eval/const_eval/
fn_queries.rs

1use rustc_hir::def_id::{DefId, LocalDefId};
2use rustc_hir::{
3    Constness, ExprKind, ForeignItemKind, ImplItem, ImplItemImplKind, ImplItemKind, Item, ItemKind,
4    Node, TraitItem, TraitItemKind, VariantData, find_attr,
5};
6use rustc_middle::query::Providers;
7use rustc_middle::ty::TyCtxt;
8
9/// Checks whether a function-like definition is considered to be `const`. Also stores constness of inherent impls.
10fn constness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Constness {
11    let node = tcx.hir_node_by_def_id(def_id);
12
13    match node {
14        Node::Ctor(VariantData::Tuple(..)) => Constness::Const,
15        Node::ForeignItem(item) if let ForeignItemKind::Fn(..) = item.kind => {
16            // Foreign functions cannot be evaluated at compile-time.
17            Constness::NotConst
18        }
19        Node::Expr(e) if let ExprKind::Closure(c) = e.kind => c.constness,
20        // FIXME(fee1-dead): extract this one out and rename this query to `fn_constness` so we don't need `is_const_fn` anymore.
21        Node::Item(i) if let ItemKind::Impl(impl_) = i.kind => impl_.constness,
22        Node::Item(Item { kind: ItemKind::Fn { sig, .. }, .. }) => sig.header.constness,
23        Node::ImplItem(ImplItem {
24            impl_kind: ImplItemImplKind::Trait { .. },
25            kind: ImplItemKind::Fn(..),
26            ..
27        }) => tcx.impl_trait_header(tcx.local_parent(def_id)).constness,
28        Node::ImplItem(ImplItem {
29            impl_kind: ImplItemImplKind::Inherent { .. },
30            kind: ImplItemKind::Fn(sig, _),
31            ..
32        }) => {
33            match sig.header.constness {
34                Constness::Const => Constness::Const,
35                // inherent impl could be const
36                Constness::NotConst => tcx.constness(tcx.local_parent(def_id)),
37            }
38        }
39        Node::TraitItem(ti @ TraitItem { kind: TraitItemKind::Fn(..), .. }) => {
40            if {
    {
            'done:
                {
                for i in tcx.hir_attrs(ti.hir_id()) {
                    #[allow(unused_imports)]
                    use rustc_hir::attrs::AttributeKind::*;
                    let i: &rustc_hir::Attribute = i;
                    match i {
                        rustc_hir::Attribute::Parsed(RustcNonConstTraitMethod) => {
                            break 'done Some(());
                        }
                        rustc_hir::Attribute::Unparsed(..) =>
                            {}
                            #[deny(unreachable_patterns)]
                            _ => {}
                    }
                }
                None
            }
        }.is_some()
}find_attr!(tcx.hir_attrs(ti.hir_id()), RustcNonConstTraitMethod) {
41                Constness::NotConst
42            } else {
43                tcx.trait_def(tcx.local_parent(def_id)).constness
44            }
45        }
46        _ => {
47            tcx.dcx().span_bug(
48                tcx.def_span(def_id),
49                ::alloc::__export::must_use({
        ::alloc::fmt::format(format_args!("should not be requesting the constness of items that can\'t be const: {1:#?}: {0:?}",
                tcx.def_kind(def_id), node))
    })format!("should not be requesting the constness of items that can't be const: {node:#?}: {:?}", tcx.def_kind(def_id))
50            )
51        }
52    }
53}
54
55fn is_promotable_const_fn(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
56    tcx.is_const_fn(def_id)
57        && match tcx.lookup_const_stability(def_id) {
58            Some(stab) => {
59                if truecfg!(debug_assertions) && stab.promotable {
60                    let sig = tcx.fn_sig(def_id);
61                    if !sig.skip_binder().safety().is_safe() {
    {
        ::core::panicking::panic_fmt(format_args!("don\'t mark const unsafe fns as promotable"));
    }
};assert!(
62                        sig.skip_binder().safety().is_safe(),
63                        "don't mark const unsafe fns as promotable",
64                        // https://github.com/rust-lang/rust/pull/53851#issuecomment-418760682
65                    );
66                }
67                stab.promotable
68            }
69            None => false,
70        }
71}
72
73pub fn provide(providers: &mut Providers) {
74    *providers = Providers { constness, is_promotable_const_fn, ..*providers };
75}
rustc_const_eval/const_eval/fn_queries.rs

rustc_const_eval/const_eval/
fn_queries.rs
