26e9990198
This allows lints and other diagnostics to refer to items by a unique ID instead of relying on whacky path resolution schemes that may break when items are relocated.
391 lines
19 KiB
Rust
391 lines
19 KiB
Rust
//! Detecting language items.
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//!
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//! Language items are items that represent concepts intrinsic to the language
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//! itself. Examples are:
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//!
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//! * Traits that specify "kinds"; e.g., "Sync", "Send".
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//!
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//! * Traits that represent operators; e.g., "Add", "Sub", "Index".
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//!
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//! * Functions called by the compiler itself.
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pub use self::LangItem::*;
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use crate::hir::def_id::DefId;
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use crate::hir::check_attr::Target;
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use crate::ty::{self, TyCtxt};
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use crate::middle::weak_lang_items;
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use crate::util::nodemap::FxHashMap;
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use syntax::ast;
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use syntax::symbol::{Symbol, sym};
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use syntax_pos::Span;
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use rustc_macros::HashStable;
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use crate::hir::itemlikevisit::ItemLikeVisitor;
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use crate::hir;
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// The actual lang items defined come at the end of this file in one handy table.
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// So you probably just want to nip down to the end.
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macro_rules! language_item_table {
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(
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$( $variant:ident, $name:expr, $method:ident, $target:path; )*
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) => {
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enum_from_u32! {
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/// A representation of all the valid language items in Rust.
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#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
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pub enum LangItem {
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$($variant,)*
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}
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}
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impl LangItem {
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/// Returns the `name` in `#[lang = "$name"]`.
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/// For example, `LangItem::EqTraitLangItem`,
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/// that is `#[lang = "eq"]` would result in `"eq"`.
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fn name(self) -> &'static str {
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match self {
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$( $variant => $name, )*
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}
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}
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}
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#[derive(HashStable)]
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pub struct LanguageItems {
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/// Mappings from lang items to their possibly found `DefId`s.
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/// The index corresponds to the order in `LangItem`.
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pub items: Vec<Option<DefId>>,
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/// Lang items that were not found during collection.
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pub missing: Vec<LangItem>,
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}
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impl LanguageItems {
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/// Construct an empty collection of lang items and no missing ones.
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pub fn new() -> Self {
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fn init_none(_: LangItem) -> Option<DefId> { None }
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Self {
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items: vec![$(init_none($variant)),*],
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missing: Vec::new(),
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}
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}
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/// Returns the mappings to the possibly found `DefId`s for each lang item.
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pub fn items(&self) -> &[Option<DefId>] {
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&*self.items
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}
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/// Requires that a given `LangItem` was bound and returns the corresponding `DefId`.
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/// If it wasn't bound, e.g. due to a missing `#[lang = "<it.name()>"]`,
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/// returns an error message as a string.
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pub fn require(&self, it: LangItem) -> Result<DefId, String> {
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self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name()))
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}
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/// Returns the kind of closure that `id`, which is one of the `Fn*` traits, corresponds to.
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/// If `id` is not one of the `Fn*` traits, `None` is returned.
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pub fn fn_trait_kind(&self, id: DefId) -> Option<ty::ClosureKind> {
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match Some(id) {
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x if x == self.fn_trait() => Some(ty::ClosureKind::Fn),
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x if x == self.fn_mut_trait() => Some(ty::ClosureKind::FnMut),
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x if x == self.fn_once_trait() => Some(ty::ClosureKind::FnOnce),
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_ => None
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}
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}
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$(
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/// Returns the corresponding `DefId` for the lang item
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#[doc = $name]
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/// if it exists.
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#[allow(dead_code)]
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pub fn $method(&self) -> Option<DefId> {
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self.items[$variant as usize]
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}
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)*
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}
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struct LanguageItemCollector<'tcx> {
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items: LanguageItems,
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tcx: TyCtxt<'tcx>,
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/// A mapping from the name of the lang item to its order and the form it must be of.
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item_refs: FxHashMap<&'static str, (usize, Target)>,
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}
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impl ItemLikeVisitor<'v> for LanguageItemCollector<'tcx> {
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fn visit_item(&mut self, item: &hir::Item) {
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if let Some((value, span)) = extract(&item.attrs) {
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let actual_target = Target::from_item(item);
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match self.item_refs.get(&*value.as_str()).cloned() {
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// Known lang item with attribute on correct target.
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Some((item_index, expected_target)) if actual_target == expected_target => {
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let def_id = self.tcx.hir().local_def_id(item.hir_id);
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self.collect_item(item_index, def_id);
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},
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// Known lang item with attribute on incorrect target.
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Some((_, expected_target)) => {
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struct_span_err!(
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self.tcx.sess, span, E0718,
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"`{}` language item must be applied to a {}",
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value, expected_target,
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).span_label(
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span,
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format!(
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"attribute should be applied to a {}, not a {}",
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expected_target, actual_target,
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),
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).emit();
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},
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// Unknown lang item.
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_ => {
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struct_span_err!(
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self.tcx.sess, span, E0522,
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"definition of an unknown language item: `{}`",
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value
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).span_label(
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span,
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format!("definition of unknown language item `{}`", value)
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).emit();
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},
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}
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}
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}
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fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
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// at present, lang items are always items, not trait items
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}
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fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
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// at present, lang items are always items, not impl items
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}
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}
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impl LanguageItemCollector<'tcx> {
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fn new(tcx: TyCtxt<'tcx>) -> LanguageItemCollector<'tcx> {
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let mut item_refs = FxHashMap::default();
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$( item_refs.insert($name, ($variant as usize, $target)); )*
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LanguageItemCollector {
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tcx,
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items: LanguageItems::new(),
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item_refs,
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}
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}
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fn collect_item(&mut self, item_index: usize, item_def_id: DefId) {
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// Check for duplicates.
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if let Some(original_def_id) = self.items.items[item_index] {
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if original_def_id != item_def_id {
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let name = LangItem::from_u32(item_index as u32).unwrap().name();
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let mut err = match self.tcx.hir().span_if_local(item_def_id) {
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Some(span) => struct_span_err!(
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self.tcx.sess,
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span,
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E0152,
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"duplicate lang item found: `{}`.",
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name),
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None => self.tcx.sess.struct_err(&format!(
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"duplicate lang item in crate `{}`: `{}`.",
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self.tcx.crate_name(item_def_id.krate),
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name)),
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};
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if let Some(span) = self.tcx.hir().span_if_local(original_def_id) {
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span_note!(&mut err, span, "first defined here.");
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} else {
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err.note(&format!("first defined in crate `{}`.",
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self.tcx.crate_name(original_def_id.krate)));
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}
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err.emit();
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}
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}
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// Matched.
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self.items.items[item_index] = Some(item_def_id);
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}
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}
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/// Extract the first `lang = "$name"` out of a list of attributes.
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/// The attributes `#[panic_handler]` and `#[alloc_error_handler]`
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/// are also extracted out when found.
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pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
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attrs.iter().find_map(|attr| Some(match attr {
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_ if attr.check_name(sym::lang) => (attr.value_str()?, attr.span),
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_ if attr.check_name(sym::panic_handler) => (sym::panic_impl, attr.span),
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_ if attr.check_name(sym::alloc_error_handler) => (sym::oom, attr.span),
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_ => return None,
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}))
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}
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/// Traverse and collect all the lang items in all crates.
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pub fn collect<'tcx>(tcx: TyCtxt<'tcx>) -> LanguageItems {
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// Initialize the collector.
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let mut collector = LanguageItemCollector::new(tcx);
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// Collect lang items in other crates.
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for &cnum in tcx.crates().iter() {
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for &(def_id, item_index) in tcx.defined_lang_items(cnum).iter() {
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collector.collect_item(item_index, def_id);
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}
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}
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// Collect lang items in this crate.
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tcx.hir().krate().visit_all_item_likes(&mut collector);
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// Extract out the found lang items.
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let LanguageItemCollector { mut items, .. } = collector;
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// Find all required but not-yet-defined lang items.
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weak_lang_items::check_crate(tcx, &mut items);
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items
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}
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// End of the macro
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}
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}
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language_item_table! {
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// Variant name, Name, Method name, Target;
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CharImplItem, "char", char_impl, Target::Impl;
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StrImplItem, "str", str_impl, Target::Impl;
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SliceImplItem, "slice", slice_impl, Target::Impl;
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SliceU8ImplItem, "slice_u8", slice_u8_impl, Target::Impl;
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StrAllocImplItem, "str_alloc", str_alloc_impl, Target::Impl;
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SliceAllocImplItem, "slice_alloc", slice_alloc_impl, Target::Impl;
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SliceU8AllocImplItem, "slice_u8_alloc", slice_u8_alloc_impl, Target::Impl;
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ConstPtrImplItem, "const_ptr", const_ptr_impl, Target::Impl;
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MutPtrImplItem, "mut_ptr", mut_ptr_impl, Target::Impl;
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I8ImplItem, "i8", i8_impl, Target::Impl;
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I16ImplItem, "i16", i16_impl, Target::Impl;
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I32ImplItem, "i32", i32_impl, Target::Impl;
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I64ImplItem, "i64", i64_impl, Target::Impl;
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I128ImplItem, "i128", i128_impl, Target::Impl;
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IsizeImplItem, "isize", isize_impl, Target::Impl;
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U8ImplItem, "u8", u8_impl, Target::Impl;
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U16ImplItem, "u16", u16_impl, Target::Impl;
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U32ImplItem, "u32", u32_impl, Target::Impl;
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U64ImplItem, "u64", u64_impl, Target::Impl;
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U128ImplItem, "u128", u128_impl, Target::Impl;
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UsizeImplItem, "usize", usize_impl, Target::Impl;
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F32ImplItem, "f32", f32_impl, Target::Impl;
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F64ImplItem, "f64", f64_impl, Target::Impl;
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F32RuntimeImplItem, "f32_runtime", f32_runtime_impl, Target::Impl;
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F64RuntimeImplItem, "f64_runtime", f64_runtime_impl, Target::Impl;
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SizedTraitLangItem, "sized", sized_trait, Target::Trait;
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UnsizeTraitLangItem, "unsize", unsize_trait, Target::Trait;
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CopyTraitLangItem, "copy", copy_trait, Target::Trait;
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CloneTraitLangItem, "clone", clone_trait, Target::Trait;
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SyncTraitLangItem, "sync", sync_trait, Target::Trait;
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FreezeTraitLangItem, "freeze", freeze_trait, Target::Trait;
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DropTraitLangItem, "drop", drop_trait, Target::Trait;
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CoerceUnsizedTraitLangItem, "coerce_unsized", coerce_unsized_trait, Target::Trait;
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DispatchFromDynTraitLangItem,"dispatch_from_dyn", dispatch_from_dyn_trait, Target::Trait;
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AddTraitLangItem, "add", add_trait, Target::Trait;
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SubTraitLangItem, "sub", sub_trait, Target::Trait;
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MulTraitLangItem, "mul", mul_trait, Target::Trait;
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DivTraitLangItem, "div", div_trait, Target::Trait;
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RemTraitLangItem, "rem", rem_trait, Target::Trait;
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NegTraitLangItem, "neg", neg_trait, Target::Trait;
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NotTraitLangItem, "not", not_trait, Target::Trait;
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BitXorTraitLangItem, "bitxor", bitxor_trait, Target::Trait;
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BitAndTraitLangItem, "bitand", bitand_trait, Target::Trait;
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BitOrTraitLangItem, "bitor", bitor_trait, Target::Trait;
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ShlTraitLangItem, "shl", shl_trait, Target::Trait;
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ShrTraitLangItem, "shr", shr_trait, Target::Trait;
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AddAssignTraitLangItem, "add_assign", add_assign_trait, Target::Trait;
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SubAssignTraitLangItem, "sub_assign", sub_assign_trait, Target::Trait;
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MulAssignTraitLangItem, "mul_assign", mul_assign_trait, Target::Trait;
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DivAssignTraitLangItem, "div_assign", div_assign_trait, Target::Trait;
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RemAssignTraitLangItem, "rem_assign", rem_assign_trait, Target::Trait;
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BitXorAssignTraitLangItem, "bitxor_assign", bitxor_assign_trait, Target::Trait;
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BitAndAssignTraitLangItem, "bitand_assign", bitand_assign_trait, Target::Trait;
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BitOrAssignTraitLangItem, "bitor_assign", bitor_assign_trait, Target::Trait;
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ShlAssignTraitLangItem, "shl_assign", shl_assign_trait, Target::Trait;
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ShrAssignTraitLangItem, "shr_assign", shr_assign_trait, Target::Trait;
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IndexTraitLangItem, "index", index_trait, Target::Trait;
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IndexMutTraitLangItem, "index_mut", index_mut_trait, Target::Trait;
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UnsafeCellTypeLangItem, "unsafe_cell", unsafe_cell_type, Target::Struct;
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VaListTypeLangItem, "va_list", va_list, Target::Struct;
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DerefTraitLangItem, "deref", deref_trait, Target::Trait;
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DerefMutTraitLangItem, "deref_mut", deref_mut_trait, Target::Trait;
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ReceiverTraitLangItem, "receiver", receiver_trait, Target::Trait;
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FnTraitLangItem, "fn", fn_trait, Target::Trait;
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FnMutTraitLangItem, "fn_mut", fn_mut_trait, Target::Trait;
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FnOnceTraitLangItem, "fn_once", fn_once_trait, Target::Trait;
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FutureTraitLangItem, "future_trait", future_trait, Target::Trait;
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GeneratorStateLangItem, "generator_state", gen_state, Target::Enum;
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GeneratorTraitLangItem, "generator", gen_trait, Target::Trait;
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UnpinTraitLangItem, "unpin", unpin_trait, Target::Trait;
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PinTypeLangItem, "pin", pin_type, Target::Struct;
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// Don't be fooled by the naming here: this lang item denotes `PartialEq`, not `Eq`.
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EqTraitLangItem, "eq", eq_trait, Target::Trait;
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PartialOrdTraitLangItem, "partial_ord", partial_ord_trait, Target::Trait;
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OrdTraitLangItem, "ord", ord_trait, Target::Trait;
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// A number of panic-related lang items. The `panic` item corresponds to
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// divide-by-zero and various panic cases with `match`. The
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// `panic_bounds_check` item is for indexing arrays.
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//
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// The `begin_unwind` lang item has a predefined symbol name and is sort of
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// a "weak lang item" in the sense that a crate is not required to have it
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// defined to use it, but a final product is required to define it
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// somewhere. Additionally, there are restrictions on crates that use a weak
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// lang item, but do not have it defined.
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PanicFnLangItem, "panic", panic_fn, Target::Fn;
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PanicBoundsCheckFnLangItem, "panic_bounds_check", panic_bounds_check_fn, Target::Fn;
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PanicInfoLangItem, "panic_info", panic_info, Target::Struct;
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PanicImplLangItem, "panic_impl", panic_impl, Target::Fn;
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// Libstd panic entry point. Necessary for const eval to be able to catch it
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BeginPanicFnLangItem, "begin_panic", begin_panic_fn, Target::Fn;
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ExchangeMallocFnLangItem, "exchange_malloc", exchange_malloc_fn, Target::Fn;
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BoxFreeFnLangItem, "box_free", box_free_fn, Target::Fn;
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DropInPlaceFnLangItem, "drop_in_place", drop_in_place_fn, Target::Fn;
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OomLangItem, "oom", oom, Target::Fn;
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AllocLayoutLangItem, "alloc_layout", alloc_layout, Target::Struct;
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StartFnLangItem, "start", start_fn, Target::Fn;
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EhPersonalityLangItem, "eh_personality", eh_personality, Target::Fn;
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EhUnwindResumeLangItem, "eh_unwind_resume", eh_unwind_resume, Target::Fn;
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MSVCTryFilterLangItem, "msvc_try_filter", msvc_try_filter, Target::Static;
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OwnedBoxLangItem, "owned_box", owned_box, Target::Struct;
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PhantomDataItem, "phantom_data", phantom_data, Target::Struct;
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ManuallyDropItem, "manually_drop", manually_drop, Target::Struct;
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MaybeUninitLangItem, "maybe_uninit", maybe_uninit, Target::Union;
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// Align offset for stride != 1, must not panic.
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AlignOffsetLangItem, "align_offset", align_offset_fn, Target::Fn;
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TerminationTraitLangItem, "termination", termination, Target::Trait;
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Arc, "arc", arc, Target::Struct;
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Rc, "rc", rc, Target::Struct;
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}
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impl<'tcx> TyCtxt<'tcx> {
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/// Returns the `DefId` for a given `LangItem`.
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/// If not found, fatally abort compilation.
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pub fn require_lang_item(&self, lang_item: LangItem, span: Option<Span>) -> DefId {
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self.lang_items().require(lang_item).unwrap_or_else(|msg| {
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if let Some(span) = span {
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self.sess.span_fatal(span, &msg)
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} else {
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self.sess.fatal(&msg)
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}
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})
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}
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}
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