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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::weak_lang_items;
use rustc_middle::middle::cstore::ExternCrate;
use rustc_middle::ty::TyCtxt;
use rustc_errors::struct_span_err;
use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LOCAL_CRATE};
use rustc_hir::itemlikevisit::ItemLikeVisitor;
use rustc_hir::lang_items::{extract, ITEM_REFS};
use rustc_hir::{LangItem, LanguageItems, Target};
use rustc_middle::ty::query::Providers;
struct LanguageItemCollector<'tcx> {
items: LanguageItems,
tcx: TyCtxt<'tcx>,
}
impl ItemLikeVisitor<'v> for LanguageItemCollector<'tcx> {
fn visit_item(&mut self, item: &hir::Item<'_>) {
if let Some((value, span)) = extract(&item.attrs) {
let actual_target = Target::from_item(item);
match ITEM_REFS.get(&*value.as_str()).cloned() {
// Known lang item with attribute on correct target.
Some((item_index, expected_target)) if actual_target == expected_target => {
let def_id = self.tcx.hir().local_def_id(item.hir_id);
self.collect_item(item_index, def_id);
}
// Known lang item with attribute on incorrect target.
Some((_, expected_target)) => {
struct_span_err!(
self.tcx.sess,
span,
E0718,
"`{}` language item must be applied to a {}",
value,
expected_target,
)
.span_label(
span,
format!(
"attribute should be applied to a {}, not a {}",
expected_target, actual_target,
),
)
.emit();
}
// Unknown lang item.
_ => {
struct_span_err!(
self.tcx.sess,
span,
E0522,
"definition of an unknown language item: `{}`",
value
)
.span_label(span, format!("definition of unknown language item `{}`", value))
.emit();
}
}
}
}
fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'_>) {
// At present, lang items are always items, not trait items.
}
fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {
// At present, lang items are always items, not impl items.
}
}
impl LanguageItemCollector<'tcx> {
fn new(tcx: TyCtxt<'tcx>) -> LanguageItemCollector<'tcx> {
LanguageItemCollector { tcx, items: LanguageItems::new() }
}
fn collect_item(&mut self, item_index: usize, item_def_id: DefId) {
// Check for duplicates.
if let Some(original_def_id) = self.items.items[item_index] {
if original_def_id != item_def_id {
let name = LangItem::from_u32(item_index as u32).unwrap().name();
let mut err = match self.tcx.hir().span_if_local(item_def_id) {
Some(span) => struct_span_err!(
self.tcx.sess,
span,
E0152,
"found duplicate lang item `{}`",
name
),
None => match self.tcx.extern_crate(item_def_id) {
Some(ExternCrate { dependency_of, .. }) => {
self.tcx.sess.struct_err(&format!(
"duplicate lang item in crate `{}` (which `{}` depends on): `{}`.",
self.tcx.crate_name(item_def_id.krate),
self.tcx.crate_name(*dependency_of),
name
))
}
_ => self.tcx.sess.struct_err(&format!(
"duplicate lang item in crate `{}`: `{}`.",
self.tcx.crate_name(item_def_id.krate),
name
)),
},
};
if let Some(span) = self.tcx.hir().span_if_local(original_def_id) {
err.span_note(span, "the lang item is first defined here");
} else {
match self.tcx.extern_crate(original_def_id) {
Some(ExternCrate { dependency_of, .. }) => {
err.note(&format!(
"the lang item is first defined in crate `{}` (which `{}` depends on)",
self.tcx.crate_name(original_def_id.krate),
self.tcx.crate_name(*dependency_of)
));
}
_ => {
err.note(&format!(
"the lang item is first defined in crate `{}`.",
self.tcx.crate_name(original_def_id.krate)
));
}
}
}
err.emit();
}
}
// Matched.
self.items.items[item_index] = Some(item_def_id);
}
}
/// Traverses and collects all the lang items in all crates.
fn collect(tcx: TyCtxt<'_>) -> LanguageItems {
// Initialize the collector.
let mut collector = LanguageItemCollector::new(tcx);
// Collect lang items in other crates.
for &cnum in tcx.crates().iter() {
for &(def_id, item_index) in tcx.defined_lang_items(cnum).iter() {
collector.collect_item(item_index, def_id);
}
}
// Collect lang items in this crate.
tcx.hir().krate().visit_all_item_likes(&mut collector);
// Extract out the found lang items.
let LanguageItemCollector { mut items, .. } = collector;
// Find all required but not-yet-defined lang items.
weak_lang_items::check_crate(tcx, &mut items);
items
}
pub fn provide(providers: &mut Providers<'_>) {
providers.get_lang_items = |tcx, id| {
assert_eq!(id, LOCAL_CRATE);
tcx.arena.alloc(collect(tcx))
};
}
|
