rustc_middle/middle/
lang_items.rs

1//! Detecting lang items.
2//!
3//! Language items are items that represent concepts intrinsic to the language
4//! itself. Examples are:
5//!
6//! * Traits that specify "kinds"; e.g., `Sync`, `Send`.
7//! * Traits that represent operators; e.g., `Add`, `Sub`, `Index`.
8//! * Functions called by the compiler itself.
9
10use rustc_hir::LangItem;
11use rustc_hir::def_id::DefId;
12use rustc_span::Span;
13use rustc_target::spec::PanicStrategy;
14
15use crate::ty::{self, TyCtxt};
16
17impl<'tcx> TyCtxt<'tcx> {
18    /// Returns the `DefId` for a given `LangItem`.
19    /// If not found, fatally aborts compilation.
20    pub fn require_lang_item(self, lang_item: LangItem, span: Option<Span>) -> DefId {
21        self.lang_items().get(lang_item).unwrap_or_else(|| {
22            self.dcx().emit_fatal(crate::error::RequiresLangItem { span, name: lang_item.name() });
23        })
24    }
25
26    pub fn is_lang_item(self, def_id: DefId, lang_item: LangItem) -> bool {
27        self.lang_items().get(lang_item) == Some(def_id)
28    }
29
30    pub fn as_lang_item(self, def_id: DefId) -> Option<LangItem> {
31        self.lang_items().from_def_id(def_id)
32    }
33
34    /// Given a [`DefId`] of one of the [`Fn`], [`FnMut`] or [`FnOnce`] traits,
35    /// returns a corresponding [`ty::ClosureKind`].
36    /// For any other [`DefId`] return `None`.
37    pub fn fn_trait_kind_from_def_id(self, id: DefId) -> Option<ty::ClosureKind> {
38        let items = self.lang_items();
39        match Some(id) {
40            x if x == items.fn_trait() => Some(ty::ClosureKind::Fn),
41            x if x == items.fn_mut_trait() => Some(ty::ClosureKind::FnMut),
42            x if x == items.fn_once_trait() => Some(ty::ClosureKind::FnOnce),
43            _ => None,
44        }
45    }
46
47    /// Given a [`DefId`] of one of the `AsyncFn`, `AsyncFnMut` or `AsyncFnOnce` traits,
48    /// returns a corresponding [`ty::ClosureKind`].
49    /// For any other [`DefId`] return `None`.
50    pub fn async_fn_trait_kind_from_def_id(self, id: DefId) -> Option<ty::ClosureKind> {
51        let items = self.lang_items();
52        match Some(id) {
53            x if x == items.async_fn_trait() => Some(ty::ClosureKind::Fn),
54            x if x == items.async_fn_mut_trait() => Some(ty::ClosureKind::FnMut),
55            x if x == items.async_fn_once_trait() => Some(ty::ClosureKind::FnOnce),
56            _ => None,
57        }
58    }
59
60    /// Given a [`ty::ClosureKind`], get the [`DefId`] of its corresponding `Fn`-family
61    /// trait, if it is defined.
62    pub fn fn_trait_kind_to_def_id(self, kind: ty::ClosureKind) -> Option<DefId> {
63        let items = self.lang_items();
64        match kind {
65            ty::ClosureKind::Fn => items.fn_trait(),
66            ty::ClosureKind::FnMut => items.fn_mut_trait(),
67            ty::ClosureKind::FnOnce => items.fn_once_trait(),
68        }
69    }
70
71    /// Given a [`ty::ClosureKind`], get the [`DefId`] of its corresponding `Fn`-family
72    /// trait, if it is defined.
73    pub fn async_fn_trait_kind_to_def_id(self, kind: ty::ClosureKind) -> Option<DefId> {
74        let items = self.lang_items();
75        match kind {
76            ty::ClosureKind::Fn => items.async_fn_trait(),
77            ty::ClosureKind::FnMut => items.async_fn_mut_trait(),
78            ty::ClosureKind::FnOnce => items.async_fn_once_trait(),
79        }
80    }
81
82    /// Returns `true` if `id` is a `DefId` of [`Fn`], [`FnMut`] or [`FnOnce`] traits.
83    pub fn is_fn_trait(self, id: DefId) -> bool {
84        self.fn_trait_kind_from_def_id(id).is_some()
85    }
86}
87
88/// Returns `true` if the specified `lang_item` must be present for this
89/// compilation.
90///
91/// Not all lang items are always required for each compilation, particularly in
92/// the case of panic=abort. In these situations some lang items are injected by
93/// crates and don't actually need to be defined in libstd.
94pub fn required(tcx: TyCtxt<'_>, lang_item: LangItem) -> bool {
95    // If we're not compiling with unwinding, we won't actually need these
96    // symbols. Other panic runtimes ensure that the relevant symbols are
97    // available to link things together, but they're never exercised.
98    match tcx.sess.panic_strategy() {
99        PanicStrategy::Abort => {
100            lang_item != LangItem::EhPersonality && lang_item != LangItem::EhCatchTypeinfo
101        }
102        PanicStrategy::Unwind => true,
103    }
104}
rustc_middle/middle/lang_items.rs

rustc_middle/middle/
lang_items.rs
