rust/src/librustc_passes/stability.rs

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//! A pass that annotates every item and method with its stability level,
//! propagating default levels lexically from parent to children ast nodes.
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use rustc::hir::map::Map;
use rustc::lint;
use rustc::middle::privacy::AccessLevels;
use rustc::middle::stability::{DeprecationEntry, Index};
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use rustc::session::parse::feature_err;
use rustc::session::Session;
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use rustc::traits::misc::can_type_implement_copy;
use rustc::ty::query::Providers;
use rustc::ty::TyCtxt;
use rustc_attr::{self as attr, Stability};
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use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_errors::struct_span_err;
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
use rustc_hir::{Generics, HirId, Item, StructField, Variant};
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use rustc_span::symbol::{sym, Symbol};
use rustc_span::Span;
use syntax::ast::Attribute;
use std::cmp::Ordering;
use std::mem::replace;
use std::num::NonZeroU32;
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#[derive(PartialEq)]
enum AnnotationKind {
// Annotation is required if not inherited from unstable parents
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Required,
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// Annotation is useless, reject it
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Prohibited,
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// Annotation itself is useless, but it can be propagated to children
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Container,
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}
// A private tree-walker for producing an Index.
struct Annotator<'a, 'tcx> {
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tcx: TyCtxt<'tcx>,
index: &'a mut Index<'tcx>,
parent_stab: Option<&'tcx Stability>,
parent_depr: Option<DeprecationEntry>,
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in_trait_impl: bool,
}
impl<'a, 'tcx> Annotator<'a, 'tcx> {
// Determine the stability for a node based on its attributes and inherited
// stability. The stability is recorded in the index and used as the parent.
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fn annotate<F>(
&mut self,
hir_id: HirId,
attrs: &[Attribute],
item_sp: Span,
kind: AnnotationKind,
visit_children: F,
) where
F: FnOnce(&mut Self),
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{
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if self.tcx.features().staged_api {
// This crate explicitly wants staged API.
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debug!("annotate(id = {:?}, attrs = {:?})", hir_id, attrs);
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if let Some(..) = attr::find_deprecation(&self.tcx.sess.parse_sess, attrs, item_sp) {
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self.tcx.sess.span_err(
item_sp,
"`#[deprecated]` cannot be used in staged API; \
use `#[rustc_deprecated]` instead",
);
}
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let (stab, const_stab) =
attr::find_stability(&self.tcx.sess.parse_sess, attrs, item_sp);
if let Some(const_stab) = const_stab {
let const_stab = self.tcx.intern_const_stability(const_stab);
self.index.const_stab_map.insert(hir_id, const_stab);
}
if let Some(mut stab) = stab {
// Error if prohibited, or can't inherit anything from a container.
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if kind == AnnotationKind::Prohibited
|| (kind == AnnotationKind::Container
&& stab.level.is_stable()
&& stab.rustc_depr.is_none())
{
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self.tcx.sess.span_err(item_sp, "This stability annotation is useless");
}
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debug!("annotate: found {:?}", stab);
// If parent is deprecated and we're not, inherit this by merging
// deprecated_since and its reason.
if let Some(parent_stab) = self.parent_stab {
if parent_stab.rustc_depr.is_some() && stab.rustc_depr.is_none() {
stab.rustc_depr = parent_stab.rustc_depr
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}
}
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let stab = self.tcx.intern_stability(stab);
// Check if deprecated_since < stable_since. If it is,
// this is *almost surely* an accident.
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if let (
&Some(attr::RustcDeprecation { since: dep_since, .. }),
&attr::Stable { since: stab_since },
) = (&stab.rustc_depr, &stab.level)
{
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// Explicit version of iter::order::lt to handle parse errors properly
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for (dep_v, stab_v) in
dep_since.as_str().split('.').zip(stab_since.as_str().split('.'))
{
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if let (Ok(dep_v), Ok(stab_v)) = (dep_v.parse::<u64>(), stab_v.parse()) {
match dep_v.cmp(&stab_v) {
Ordering::Less => {
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self.tcx.sess.span_err(
item_sp,
"An API can't be stabilized \
after it is deprecated",
);
break;
}
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Ordering::Equal => continue,
Ordering::Greater => break,
}
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} else {
// Act like it isn't less because the question is now nonsensical,
// and this makes us not do anything else interesting.
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self.tcx.sess.span_err(
item_sp,
"Invalid stability or deprecation \
version found",
);
break;
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}
}
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}
self.index.stab_map.insert(hir_id, stab);
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let orig_parent_stab = replace(&mut self.parent_stab, Some(stab));
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visit_children(self);
self.parent_stab = orig_parent_stab;
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} else {
debug!("annotate: not found, parent = {:?}", self.parent_stab);
if let Some(stab) = self.parent_stab {
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if stab.level.is_unstable() {
self.index.stab_map.insert(hir_id, stab);
}
}
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visit_children(self);
}
} else {
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// Emit errors for non-staged-api crates.
let unstable_attrs = [
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sym::unstable,
sym::stable,
sym::rustc_deprecated,
sym::rustc_const_unstable,
sym::rustc_const_stable,
];
for attr in attrs {
let name = attr.name_or_empty();
if unstable_attrs.contains(&name) {
attr::mark_used(attr);
struct_span_err!(
self.tcx.sess,
attr.span,
E0734,
"stability attributes may not be used outside of the standard library",
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)
.emit();
}
}
// Propagate unstability. This can happen even for non-staged-api crates in case
// -Zforce-unstable-if-unmarked is set.
if let Some(stab) = self.parent_stab {
if stab.level.is_unstable() {
self.index.stab_map.insert(hir_id, stab);
}
}
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if let Some(depr) = attr::find_deprecation(&self.tcx.sess.parse_sess, attrs, item_sp) {
if kind == AnnotationKind::Prohibited {
self.tcx.sess.span_err(item_sp, "This deprecation annotation is useless");
}
// `Deprecation` is just two pointers, no need to intern it
let depr_entry = DeprecationEntry::local(depr, hir_id);
self.index.depr_map.insert(hir_id, depr_entry.clone());
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let orig_parent_depr = replace(&mut self.parent_depr, Some(depr_entry));
visit_children(self);
self.parent_depr = orig_parent_depr;
} else if let Some(parent_depr) = self.parent_depr.clone() {
self.index.depr_map.insert(hir_id, parent_depr);
visit_children(self);
} else {
visit_children(self);
}
}
}
}
impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
/// Because stability levels are scoped lexically, we want to walk
/// nested items in the context of the outer item, so enable
/// deep-walking.
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type Map = Map<'tcx>;
fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
NestedVisitorMap::All(&self.tcx.hir())
}
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fn visit_item(&mut self, i: &'tcx Item<'tcx>) {
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let orig_in_trait_impl = self.in_trait_impl;
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let mut kind = AnnotationKind::Required;
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match i.kind {
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// Inherent impls and foreign modules serve only as containers for other items,
// they don't have their own stability. They still can be annotated as unstable
// and propagate this unstability to children, but this annotation is completely
// optional. They inherit stability from their parents when unannotated.
hir::ItemKind::Impl { of_trait: None, .. } | hir::ItemKind::ForeignMod(..) => {
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self.in_trait_impl = false;
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kind = AnnotationKind::Container;
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}
hir::ItemKind::Impl { of_trait: Some(_), .. } => {
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self.in_trait_impl = true;
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}
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hir::ItemKind::Struct(ref sd, _) => {
if let Some(ctor_hir_id) = sd.ctor_hir_id() {
self.annotate(ctor_hir_id, &i.attrs, i.span, AnnotationKind::Required, |_| {})
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}
}
_ => {}
}
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self.annotate(i.hir_id, &i.attrs, i.span, kind, |v| intravisit::walk_item(v, i));
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self.in_trait_impl = orig_in_trait_impl;
}
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fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem<'tcx>) {
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self.annotate(ti.hir_id, &ti.attrs, ti.span, AnnotationKind::Required, |v| {
intravisit::walk_trait_item(v, ti);
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});
}
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fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem<'tcx>) {
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let kind =
if self.in_trait_impl { AnnotationKind::Prohibited } else { AnnotationKind::Required };
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self.annotate(ii.hir_id, &ii.attrs, ii.span, kind, |v| {
intravisit::walk_impl_item(v, ii);
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});
}
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fn visit_variant(&mut self, var: &'tcx Variant<'tcx>, g: &'tcx Generics<'tcx>, item_id: HirId) {
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self.annotate(var.id, &var.attrs, var.span, AnnotationKind::Required, |v| {
if let Some(ctor_hir_id) = var.data.ctor_hir_id() {
v.annotate(ctor_hir_id, &var.attrs, var.span, AnnotationKind::Required, |_| {});
}
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intravisit::walk_variant(v, var, g, item_id)
})
}
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fn visit_struct_field(&mut self, s: &'tcx StructField<'tcx>) {
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self.annotate(s.hir_id, &s.attrs, s.span, AnnotationKind::Required, |v| {
intravisit::walk_struct_field(v, s);
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});
}
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fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem<'tcx>) {
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self.annotate(i.hir_id, &i.attrs, i.span, AnnotationKind::Required, |v| {
intravisit::walk_foreign_item(v, i);
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});
}
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fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef<'tcx>) {
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self.annotate(md.hir_id, &md.attrs, md.span, AnnotationKind::Required, |_| {});
}
}
struct MissingStabilityAnnotations<'a, 'tcx> {
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tcx: TyCtxt<'tcx>,
access_levels: &'a AccessLevels,
}
impl<'a, 'tcx> MissingStabilityAnnotations<'a, 'tcx> {
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fn check_missing_stability(&self, hir_id: HirId, span: Span, name: &str) {
let stab = self.tcx.stability().local_stability(hir_id);
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let is_error =
!self.tcx.sess.opts.test && stab.is_none() && self.access_levels.is_reachable(hir_id);
if is_error {
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self.tcx.sess.span_err(span, &format!("{} has missing stability attribute", name));
}
}
}
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impl<'a, 'tcx> Visitor<'tcx> for MissingStabilityAnnotations<'a, 'tcx> {
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type Map = Map<'tcx>;
fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
NestedVisitorMap::OnlyBodies(&self.tcx.hir())
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}
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fn visit_item(&mut self, i: &'tcx Item<'tcx>) {
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match i.kind {
// Inherent impls and foreign modules serve only as containers for other items,
// they don't have their own stability. They still can be annotated as unstable
// and propagate this unstability to children, but this annotation is completely
// optional. They inherit stability from their parents when unannotated.
hir::ItemKind::Impl { of_trait: None, .. } | hir::ItemKind::ForeignMod(..) => {}
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_ => self.check_missing_stability(i.hir_id, i.span, i.kind.descriptive_variant()),
}
intravisit::walk_item(self, i)
}
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fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem<'tcx>) {
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self.check_missing_stability(ti.hir_id, ti.span, "item");
intravisit::walk_trait_item(self, ti);
}
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fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem<'tcx>) {
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let impl_def_id = self.tcx.hir().local_def_id(self.tcx.hir().get_parent_item(ii.hir_id));
if self.tcx.impl_trait_ref(impl_def_id).is_none() {
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self.check_missing_stability(ii.hir_id, ii.span, "item");
}
intravisit::walk_impl_item(self, ii);
}
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fn visit_variant(&mut self, var: &'tcx Variant<'tcx>, g: &'tcx Generics<'tcx>, item_id: HirId) {
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self.check_missing_stability(var.id, var.span, "variant");
intravisit::walk_variant(self, var, g, item_id);
}
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fn visit_struct_field(&mut self, s: &'tcx StructField<'tcx>) {
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self.check_missing_stability(s.hir_id, s.span, "field");
intravisit::walk_struct_field(self, s);
}
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fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem<'tcx>) {
self.check_missing_stability(i.hir_id, i.span, i.kind.descriptive_variant());
intravisit::walk_foreign_item(self, i);
}
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fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef<'tcx>) {
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self.check_missing_stability(md.hir_id, md.span, "macro");
}
}
fn new_index(tcx: TyCtxt<'tcx>) -> Index<'tcx> {
let is_staged_api =
tcx.sess.opts.debugging_opts.force_unstable_if_unmarked || tcx.features().staged_api;
let mut staged_api = FxHashMap::default();
staged_api.insert(LOCAL_CRATE, is_staged_api);
let mut index = Index {
staged_api,
stab_map: Default::default(),
const_stab_map: Default::default(),
depr_map: Default::default(),
active_features: Default::default(),
};
let active_lib_features = &tcx.features().declared_lib_features;
let active_lang_features = &tcx.features().declared_lang_features;
// Put the active features into a map for quick lookup.
index.active_features = active_lib_features
.iter()
.map(|&(s, ..)| s)
.chain(active_lang_features.iter().map(|&(s, ..)| s))
.collect();
{
let krate = tcx.hir().krate();
let mut annotator = Annotator {
tcx,
index: &mut index,
parent_stab: None,
parent_depr: None,
in_trait_impl: false,
};
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// If the `-Z force-unstable-if-unmarked` flag is passed then we provide
// a parent stability annotation which indicates that this is private
// with the `rustc_private` feature. This is intended for use when
// compiling librustc crates themselves so we can leverage crates.io
// while maintaining the invariant that all sysroot crates are unstable
// by default and are unable to be used.
if tcx.sess.opts.debugging_opts.force_unstable_if_unmarked {
let reason = "this crate is being loaded from the sysroot, an \
unstable location; did you mean to load this crate \
from crates.io via `Cargo.toml` instead?";
let stability = tcx.intern_stability(Stability {
level: attr::StabilityLevel::Unstable {
reason: Some(Symbol::intern(reason)),
issue: NonZeroU32::new(27812),
is_soft: false,
},
feature: sym::rustc_private,
rustc_depr: None,
});
annotator.parent_stab = Some(stability);
}
annotator.annotate(
hir::CRATE_HIR_ID,
&krate.attrs,
krate.span,
AnnotationKind::Required,
|v| intravisit::walk_crate(v, krate),
);
}
return index;
}
/// Cross-references the feature names of unstable APIs with enabled
/// features and possibly prints errors.
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fn check_mod_unstable_api_usage(tcx: TyCtxt<'_>, module_def_id: DefId) {
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tcx.hir().visit_item_likes_in_module(module_def_id, &mut Checker { tcx }.as_deep_visitor());
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}
pub(crate) fn provide(providers: &mut Providers<'_>) {
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*providers = Providers { check_mod_unstable_api_usage, ..*providers };
providers.stability_index = |tcx, cnum| {
assert_eq!(cnum, LOCAL_CRATE);
tcx.arena.alloc(new_index(tcx))
};
}
struct Checker<'tcx> {
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tcx: TyCtxt<'tcx>,
}
impl Visitor<'tcx> for Checker<'tcx> {
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type Map = Map<'tcx>;
/// Because stability levels are scoped lexically, we want to walk
/// nested items in the context of the outer item, so enable
/// deep-walking.
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fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> {
NestedVisitorMap::OnlyBodies(&self.tcx.hir())
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}
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fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
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match item.kind {
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hir::ItemKind::ExternCrate(_) => {
// compiler-generated `extern crate` items have a dummy span.
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if item.span.is_dummy() {
return;
}
let def_id = self.tcx.hir().local_def_id(item.hir_id);
let cnum = match self.tcx.extern_mod_stmt_cnum(def_id) {
Some(cnum) => cnum,
None => return,
};
let def_id = DefId { krate: cnum, index: CRATE_DEF_INDEX };
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self.tcx.check_stability(def_id, Some(item.hir_id), item.span);
}
// For implementations of traits, check the stability of each item
// individually as it's possible to have a stable trait with unstable
// items.
hir::ItemKind::Impl { of_trait: Some(ref t), items, .. } => {
if let Res::Def(DefKind::Trait, trait_did) = t.path.res {
for impl_item_ref in items {
let impl_item = self.tcx.hir().impl_item(impl_item_ref.id);
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let trait_item_def_id = self
.tcx
.associated_items(trait_did)
.iter()
.find(|item| item.ident.name == impl_item.ident.name)
.map(|item| item.def_id);
if let Some(def_id) = trait_item_def_id {
// Pass `None` to skip deprecation warnings.
self.tcx.check_stability(def_id, None, impl_item.span);
}
}
}
}
// There's no good place to insert stability check for non-Copy unions,
// so semi-randomly perform it here in stability.rs
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hir::ItemKind::Union(..) if !self.tcx.features().untagged_unions => {
let def_id = self.tcx.hir().local_def_id(item.hir_id);
let adt_def = self.tcx.adt_def(def_id);
let ty = self.tcx.type_of(def_id);
if adt_def.has_dtor(self.tcx) {
feature_err(
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&self.tcx.sess.parse_sess,
sym::untagged_unions,
item.span,
"unions with `Drop` implementations are unstable",
)
.emit();
} else {
let param_env = self.tcx.param_env(def_id);
if !can_type_implement_copy(self.tcx, param_env, ty).is_ok() {
feature_err(
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&self.tcx.sess.parse_sess,
sym::untagged_unions,
item.span,
"unions with non-`Copy` fields are unstable",
)
.emit();
}
}
}
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_ => (/* pass */),
}
intravisit::walk_item(self, item);
}
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fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, id: hir::HirId) {
if let Some(def_id) = path.res.opt_def_id() {
self.tcx.check_stability(def_id, Some(id), path.span)
}
intravisit::walk_path(self, path)
}
}
/// Given the list of enabled features that were not language features (i.e., that
/// were expected to be library features), and the list of features used from
/// libraries, identify activated features that don't exist and error about them.
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pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
if tcx.stability().staged_api[&LOCAL_CRATE] {
let krate = tcx.hir().krate();
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let mut missing = MissingStabilityAnnotations { tcx, access_levels };
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missing.check_missing_stability(hir::CRATE_HIR_ID, krate.span, "crate");
intravisit::walk_crate(&mut missing, krate);
krate.visit_all_item_likes(&mut missing.as_deep_visitor());
}
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let declared_lang_features = &tcx.features().declared_lang_features;
let mut lang_features = FxHashSet::default();
for &(feature, span, since) in declared_lang_features {
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if let Some(since) = since {
// Warn if the user has enabled an already-stable lang feature.
unnecessary_stable_feature_lint(tcx, span, feature, since);
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}
if !lang_features.insert(feature) {
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// Warn if the user enables a lang feature multiple times.
duplicate_feature_err(tcx.sess, span, feature);
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}
}
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let declared_lib_features = &tcx.features().declared_lib_features;
let mut remaining_lib_features = FxHashMap::default();
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for (feature, span) in declared_lib_features {
if remaining_lib_features.contains_key(&feature) {
// Warn if the user enables a lib feature multiple times.
duplicate_feature_err(tcx.sess, *span, *feature);
}
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remaining_lib_features.insert(feature, span.clone());
}
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// `stdbuild` has special handling for `libc`, so we need to
// recognise the feature when building std.
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// Likewise, libtest is handled specially, so `test` isn't
// available as we'd like it to be.
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// FIXME: only remove `libc` when `stdbuild` is active.
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// FIXME: remove special casing for `test`.
remaining_lib_features.remove(&Symbol::intern("libc"));
remaining_lib_features.remove(&sym::test);
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let check_features = |remaining_lib_features: &mut FxHashMap<_, _>, defined_features: &[_]| {
for &(feature, since) in defined_features {
if let Some(since) = since {
if let Some(span) = remaining_lib_features.get(&feature) {
// Warn if the user has enabled an already-stable lib feature.
unnecessary_stable_feature_lint(tcx, *span, feature, since);
}
}
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remaining_lib_features.remove(&feature);
if remaining_lib_features.is_empty() {
break;
}
}
};
// We always collect the lib features declared in the current crate, even if there are
// no unknown features, because the collection also does feature attribute validation.
let local_defined_features = tcx.lib_features().to_vec();
if !remaining_lib_features.is_empty() {
check_features(&mut remaining_lib_features, &local_defined_features);
for &cnum in &*tcx.crates() {
if remaining_lib_features.is_empty() {
break;
}
check_features(&mut remaining_lib_features, tcx.defined_lib_features(cnum));
}
}
for (feature, span) in remaining_lib_features {
struct_span_err!(tcx.sess, span, E0635, "unknown feature `{}`", feature).emit();
}
// FIXME(#44232): the `used_features` table no longer exists, so we
// don't lint about unused features. We should reenable this one day!
}
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fn unnecessary_stable_feature_lint(tcx: TyCtxt<'_>, span: Span, feature: Symbol, since: Symbol) {
tcx.struct_span_lint_hir(lint::builtin::STABLE_FEATURES, hir::CRATE_HIR_ID, span, |lint| {
lint.build(&format!(
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"the feature `{}` has been stable since {} and no longer requires \
an attribute to enable",
feature, since
)).emit();
}
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);
}
fn duplicate_feature_err(sess: &Session, span: Span, feature: Symbol) {
struct_span_err!(sess, span, E0636, "the feature `{}` has already been declared", feature)
.emit();
Preliminary feature staging This partially implements the feature staging described in the [release channel RFC][rc]. It does not yet fully conform to the RFC as written, but does accomplish its goals sufficiently for the 1.0 alpha release. It has three primary user-visible effects: * On the nightly channel, use of unstable APIs generates a warning. * On the beta channel, use of unstable APIs generates a warning. * On the beta channel, use of feature gates generates a warning. Code that does not trigger these warnings is considered 'stable', modulo pre-1.0 bugs. Disabling the warnings for unstable APIs continues to be done in the existing (i.e. old) style, via `#[allow(...)]`, not that specified in the RFC. I deem this marginally acceptable since any code that must do this is not using the stable dialect of Rust. Use of feature gates is itself gated with the new 'unstable_features' lint, on nightly set to 'allow', and on beta 'warn'. The attribute scheme used here corresponds to an older version of the RFC, with the `#[staged_api]` crate attribute toggling the staging behavior of the stability attributes, but the user impact is only in-tree so I'm not concerned about having to make design changes later (and I may ultimately prefer the scheme here after all, with the `#[staged_api]` crate attribute). Since the Rust codebase itself makes use of unstable features the compiler and build system to a midly elaborate dance to allow it to bootstrap while disobeying these lints (which would otherwise be errors because Rust builds with `-D warnings`). This patch includes one significant hack that causes a regression. Because the `format_args!` macro emits calls to unstable APIs it would trigger the lint. I added a hack to the lint to make it not trigger, but this in turn causes arguments to `println!` not to be checked for feature gates. I don't presently understand macro expansion well enough to fix. This is bug #20661. Closes #16678 [rc]: https://github.com/rust-lang/rfcs/blob/master/text/0507-release-channels.md
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}