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//! Detecting language items.
//!
//! Language items are items that represent concepts intrinsic to the language
//! itself. Examples are:
//!
//! * Traits that specify "kinds"; e.g., `Sync`, `Send`.
//! * Traits that represent operators; e.g., `Add`, `Sub`, `Index`.
//! * Functions called by the compiler itself.
use crate::ty::{self, TyCtxt};
use rustc_hir::def_id::DefId;
use rustc_hir::LangItem;
use rustc_span::Span;
use rustc_target::spec::PanicStrategy;
impl<'tcx> TyCtxt<'tcx> {
/// Returns the `DefId` for a given `LangItem`.
/// If not found, fatally aborts compilation.
pub fn require_lang_item(self, lang_item: LangItem, span: Option<Span>) -> DefId {
self.lang_items().require(lang_item).unwrap_or_else(|msg| {
if let Some(span) = span {
self.sess.span_fatal(span, &msg)
} else {
self.sess.fatal(&msg)
}
})
}
pub fn fn_trait_kind_from_lang_item(self, id: DefId) -> Option<ty::ClosureKind> {
let items = self.lang_items();
match Some(id) {
x if x == items.fn_trait() => Some(ty::ClosureKind::Fn),
x if x == items.fn_mut_trait() => Some(ty::ClosureKind::FnMut),
x if x == items.fn_once_trait() => Some(ty::ClosureKind::FnOnce),
_ => None,
}
}
pub fn is_weak_lang_item(self, item_def_id: DefId) -> bool {
self.lang_items().is_weak_lang_item(item_def_id)
}
}
/// Returns `true` if the specified `lang_item` must be present for this
/// compilation.
///
/// Not all lang items are always required for each compilation, particularly in
/// the case of panic=abort. In these situations some lang items are injected by
/// crates and don't actually need to be defined in libstd.
pub fn required(tcx: TyCtxt<'_>, lang_item: LangItem) -> bool {
// If we're not compiling with unwinding, we won't actually need these
// symbols. Other panic runtimes ensure that the relevant symbols are
// available to link things together, but they're never exercised.
match tcx.sess.panic_strategy() {
PanicStrategy::Abort => {
lang_item != LangItem::EhPersonality && lang_item != LangItem::EhCatchTypeinfo
}
PanicStrategy::Unwind => true,
}
}
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