rust/src/librustc/middle/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.
pub use self::StabilityLevel::*;
use crate::lint::{self, Lint, in_derive_expansion};
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use crate::hir::{self, Item, Generics, StructField, Variant, HirId};
use crate::hir::def::{Res, DefKind};
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use crate::hir::def_id::{CrateNum, CRATE_DEF_INDEX, DefId, LOCAL_CRATE};
use crate::hir::intravisit::{self, Visitor, NestedVisitorMap};
use crate::ty::query::Providers;
use crate::middle::privacy::AccessLevels;
use crate::session::{DiagnosticMessageId, Session};
use syntax::symbol::{Symbol, sym};
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use syntax_pos::{Span, MultiSpan};
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use syntax::ast::Attribute;
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use syntax::errors::Applicability;
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use syntax::feature_gate::{GateIssue, emit_feature_err};
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use syntax::attr::{self, Stability, Deprecation};
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use crate::ty::{self, TyCtxt};
use crate::util::nodemap::{FxHashSet, FxHashMap};
use std::mem::replace;
use std::cmp::Ordering;
#[derive(RustcEncodable, RustcDecodable, PartialEq, PartialOrd, Clone, Copy, Debug, Eq, Hash)]
pub enum StabilityLevel {
Unstable,
Stable,
}
impl StabilityLevel {
pub fn from_attr_level(level: &attr::StabilityLevel) -> Self {
if level.is_stable() { Stable } else { Unstable }
}
}
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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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}
/// An entry in the `depr_map`.
#[derive(Clone)]
pub struct DeprecationEntry {
/// The metadata of the attribute associated with this entry.
pub attr: Deprecation,
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/// The `DefId` where the attr was originally attached. `None` for non-local
/// `DefId`'s.
origin: Option<HirId>,
}
impl_stable_hash_for!(struct self::DeprecationEntry {
attr,
origin
});
impl DeprecationEntry {
fn local(attr: Deprecation, id: HirId) -> DeprecationEntry {
DeprecationEntry {
attr,
origin: Some(id),
}
}
pub fn external(attr: Deprecation) -> DeprecationEntry {
DeprecationEntry {
attr,
origin: None,
}
}
pub fn same_origin(&self, other: &DeprecationEntry) -> bool {
match (self.origin, other.origin) {
(Some(o1), Some(o2)) => o1 == o2,
_ => false
}
}
}
/// A stability index, giving the stability level for items and methods.
pub struct Index<'tcx> {
/// This is mostly a cache, except the stabilities of local items
/// are filled by the annotator.
stab_map: FxHashMap<HirId, &'tcx Stability>,
depr_map: FxHashMap<HirId, DeprecationEntry>,
/// Maps for each crate whether it is part of the staged API.
staged_api: FxHashMap<CrateNum, bool>,
/// Features enabled for this crate.
active_features: FxHashSet<Symbol>,
}
impl_stable_hash_for!(struct self::Index<'tcx> {
stab_map,
depr_map,
staged_api,
active_features
});
// 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],
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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) {
self.tcx.sess.span_err(item_sp, "`#[deprecated]` cannot be used in staged API; \
use `#[rustc_deprecated]` instead");
}
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if let Some(mut stab) = attr::find_stability(&self.tcx.sess.parse_sess,
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attrs, item_sp) {
// 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.clone()
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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.
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
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 => {
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.
self.tcx.sess.span_err(item_sp, "Invalid stability or deprecation \
version found");
break
}
}
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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.
for attr in attrs {
let name = attr.name_or_empty();
if [sym::unstable, sym::stable, sym::rustc_deprecated].contains(&name) {
attr::mark_used(attr);
self.tcx.sess.span_err(attr.span, "stability attributes may not be used \
outside of the standard library");
}
}
// 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());
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.
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::All(&self.tcx.hir())
}
fn visit_item(&mut self, i: &'tcx Item) {
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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.node {
// 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.
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hir::ItemKind::Impl(.., None, _, _) | hir::ItemKind::ForeignMod(..) => {
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self.in_trait_impl = false;
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kind = AnnotationKind::Container;
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}
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hir::ItemKind::Impl(.., 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;
}
fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem) {
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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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});
}
fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem) {
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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, g: &'tcx Generics, item_id: HirId) {
self.annotate(var.node.id, &var.node.attrs, var.span, AnnotationKind::Required,
|v| {
if let Some(ctor_hir_id) = var.node.data.ctor_hir_id() {
v.annotate(ctor_hir_id, &var.node.attrs, var.span, AnnotationKind::Required,
|_| {});
}
intravisit::walk_variant(v, var, g, item_id)
})
}
fn visit_struct_field(&mut self, s: &'tcx StructField) {
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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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});
}
fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem) {
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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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});
}
fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef) {
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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);
let is_error = !self.tcx.sess.opts.test &&
stab.is_none() &&
self.access_levels.is_reachable(hir_id);
if is_error {
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> {
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::OnlyBodies(&self.tcx.hir())
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}
fn visit_item(&mut self, i: &'tcx Item) {
match i.node {
// 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.
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hir::ItemKind::Impl(.., None, _, _) | hir::ItemKind::ForeignMod(..) => {}
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_ => self.check_missing_stability(i.hir_id, i.span, i.node.descriptive_variant())
}
intravisit::walk_item(self, i)
}
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fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem) {
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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) {
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let impl_def_id = self.tcx.hir().local_def_id_from_hir_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, g: &'tcx Generics, item_id: HirId) {
self.check_missing_stability(var.node.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) {
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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) {
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self.check_missing_stability(i.hir_id, i.span, i.node.descriptive_variant());
intravisit::walk_foreign_item(self, i);
}
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fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef) {
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self.check_missing_stability(md.hir_id, md.span, "macro");
}
}
impl<'tcx> Index<'tcx> {
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pub fn new(tcx: TyCtxt<'tcx>) -> Index<'tcx> {
let is_staged_api =
tcx.sess.opts.debugging_opts.force_unstable_if_unmarked ||
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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(),
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(|&(ref s, ..)| s.clone())
.chain(active_lang_features.iter().map(|&(ref s, ..)| s.clone()))
.collect();
{
let krate = tcx.hir().krate();
let mut annotator = Annotator {
tcx,
index: &mut index,
parent_stab: None,
parent_depr: None,
in_trait_impl: false,
};
// 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 {
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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: 27812,
},
feature: sym::rustc_private,
rustc_depr: None,
const_stability: None,
promotable: false,
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allow_const_fn_ptr: false,
});
annotator.parent_stab = Some(stability);
}
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annotator.annotate(hir::CRATE_HIR_ID,
&krate.attrs,
krate.span,
AnnotationKind::Required,
|v| intravisit::walk_crate(v, krate));
}
return index;
}
pub fn local_stability(&self, id: HirId) -> Option<&'tcx Stability> {
self.stab_map.get(&id).cloned()
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}
pub fn local_deprecation_entry(&self, id: HirId) -> Option<DeprecationEntry> {
self.depr_map.get(&id).cloned()
}
}
/// 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>(tcx: TyCtxt<'tcx>, 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 fn provide(providers: &mut Providers<'_>) {
*providers = Providers {
check_mod_unstable_api_usage,
..*providers
};
}
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/// Checks whether an item marked with `deprecated(since="X")` is currently
/// deprecated (i.e., whether X is not greater than the current rustc version).
pub fn deprecation_in_effect(since: &str) -> bool {
fn parse_version(ver: &str) -> Vec<u32> {
// We ignore non-integer components of the version (e.g., "nightly").
ver.split(|c| c == '.' || c == '-').flat_map(|s| s.parse()).collect()
}
if let Some(rustc) = option_env!("CFG_RELEASE") {
let since: Vec<u32> = parse_version(since);
let rustc: Vec<u32> = parse_version(rustc);
// We simply treat invalid `since` attributes as relating to a previous
// Rust version, thus always displaying the warning.
if since.len() != 3 {
return true;
}
since <= rustc
} else {
// By default, a deprecation warning applies to
// the current version of the compiler.
true
}
}
struct Checker<'tcx> {
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tcx: TyCtxt<'tcx>,
}
/// Result of `TyCtxt::eval_stability`.
pub enum EvalResult {
/// We can use the item because it is stable or we provided the
/// corresponding feature gate.
Allow,
/// We cannot use the item because it is unstable and we did not provide the
/// corresponding feature gate.
Deny {
feature: Symbol,
reason: Option<Symbol>,
issue: u32,
},
/// The item does not have the `#[stable]` or `#[unstable]` marker assigned.
Unmarked,
}
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impl<'tcx> TyCtxt<'tcx> {
// See issue #38412.
fn skip_stability_check_due_to_privacy(self, mut def_id: DefId) -> bool {
// Check if `def_id` is a trait method.
match self.def_kind(def_id) {
Some(DefKind::Method) |
Some(DefKind::AssocTy) |
Some(DefKind::AssocConst) => {
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if let ty::TraitContainer(trait_def_id) = self.associated_item(def_id).container {
// Trait methods do not declare visibility (even
// for visibility info in cstore). Use containing
// trait instead, so methods of `pub` traits are
// themselves considered `pub`.
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def_id = trait_def_id;
}
}
_ => {}
}
let visibility = self.visibility(def_id);
match visibility {
// Must check stability for `pub` items.
ty::Visibility::Public => false,
// These are not visible outside crate; therefore
// stability markers are irrelevant, if even present.
ty::Visibility::Restricted(..) |
ty::Visibility::Invisible => true,
}
}
/// Evaluates the stability of an item.
///
/// Returns `EvalResult::Allow` if the item is stable, or unstable but the corresponding
/// `#![feature]` has been provided. Returns `EvalResult::Deny` which describes the offending
/// unstable feature otherwise.
///
/// If `id` is `Some(_)`, this function will also check if the item at `def_id` has been
/// deprecated. If the item is indeed deprecated, we will emit a deprecation lint attached to
/// `id`.
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pub fn eval_stability(self, def_id: DefId, id: Option<HirId>, span: Span) -> EvalResult {
let lint_deprecated = |def_id: DefId,
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id: HirId,
note: Option<Symbol>,
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suggestion: Option<Symbol>,
message: &str,
lint: &'static Lint| {
if in_derive_expansion(span) {
return;
}
let msg = if let Some(note) = note {
format!("{}: {}", message, note)
} else {
format!("{}", message)
};
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let mut diag = self.struct_span_lint_hir(lint, id, span, &msg);
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if let Some(suggestion) = suggestion {
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if let hir::Node::Expr(_) = self.hir().get(id) {
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diag.span_suggestion(
span,
"replace the use of the deprecated item",
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suggestion.to_string(),
Applicability::MachineApplicable,
);
}
}
diag.emit();
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if id == hir::DUMMY_HIR_ID {
span_bug!(span, "emitted a {} lint with dummy HIR id: {:?}", lint.name, def_id);
}
};
// Deprecated attributes apply in-crate and cross-crate.
if let Some(id) = id {
if let Some(depr_entry) = self.lookup_deprecation_entry(def_id) {
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let parent_def_id = self.hir().local_def_id_from_hir_id(
self.hir().get_parent_item(id));
let skip = self.lookup_deprecation_entry(parent_def_id)
.map_or(false, |parent_depr| parent_depr.same_origin(&depr_entry));
if !skip {
let path = self.def_path_str(def_id);
let message = format!("use of deprecated item '{}'", path);
lint_deprecated(def_id,
id,
depr_entry.attr.note,
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None,
&message,
lint::builtin::DEPRECATED);
}
};
}
let is_staged_api = self.lookup_stability(DefId {
index: CRATE_DEF_INDEX,
..def_id
}).is_some();
if !is_staged_api {
return EvalResult::Allow;
}
let stability = self.lookup_stability(def_id);
debug!("stability: \
inspecting def_id={:?} span={:?} of stability={:?}", def_id, span, stability);
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if let Some(id) = id {
if let Some(stability) = stability {
if let Some(depr) = &stability.rustc_depr {
let path = self.def_path_str(def_id);
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if deprecation_in_effect(&depr.since.as_str()) {
let message = format!("use of deprecated item '{}'", path);
lint_deprecated(def_id,
id,
Some(depr.reason),
depr.suggestion,
&message,
lint::builtin::DEPRECATED);
} else {
let message = format!("use of item '{}' \
that will be deprecated in future version {}",
path,
depr.since);
lint_deprecated(def_id,
id,
Some(depr.reason),
depr.suggestion,
&message,
lint::builtin::DEPRECATED_IN_FUTURE);
}
}
}
}
// Only the cross-crate scenario matters when checking unstable APIs
let cross_crate = !def_id.is_local();
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if !cross_crate {
return EvalResult::Allow;
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}
// Issue #38412: private items lack stability markers.
if self.skip_stability_check_due_to_privacy(def_id) {
return EvalResult::Allow;
}
match stability {
Some(&Stability { level: attr::Unstable { reason, issue }, feature, .. }) => {
if span.allows_unstable(feature) {
debug!("stability: skipping span={:?} since it is internal", span);
return EvalResult::Allow;
}
if self.stability().active_features.contains(&feature) {
return EvalResult::Allow;
}
// When we're compiling the compiler itself we may pull in
// crates from crates.io, but those crates may depend on other
// crates also pulled in from crates.io. We want to ideally be
// able to compile everything without requiring upstream
// modifications, so in the case that this looks like a
// `rustc_private` crate (e.g., a compiler crate) and we also have
// the `-Z force-unstable-if-unmarked` flag present (we're
// compiling a compiler crate), then let this missing feature
// annotation slide.
if feature == sym::rustc_private && issue == 27812 {
if self.sess.opts.debugging_opts.force_unstable_if_unmarked {
return EvalResult::Allow;
}
}
EvalResult::Deny { feature, reason, issue }
}
Some(_) => {
// Stable APIs are always ok to call and deprecated APIs are
// handled by the lint emitting logic above.
EvalResult::Allow
}
None => {
EvalResult::Unmarked
}
}
}
/// Checks if an item is stable or error out.
///
/// If the item defined by `def_id` is unstable and the corresponding `#![feature]` does not
/// exist, emits an error.
///
/// Additionally, this function will also check if the item is deprecated. If so, and `id` is
/// not `None`, a deprecated lint attached to `id` will be emitted.
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pub fn check_stability(self, def_id: DefId, id: Option<HirId>, span: Span) {
match self.eval_stability(def_id, id, span) {
EvalResult::Allow => {}
EvalResult::Deny { feature, reason, issue } => {
let msg = match reason {
Some(r) => format!("use of unstable library feature '{}': {}", feature, r),
None => format!("use of unstable library feature '{}'", &feature)
};
let msp: MultiSpan = span.into();
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let cm = &self.sess.parse_sess.source_map();
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let span_key = msp.primary_span().and_then(|sp: Span|
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if !sp.is_dummy() {
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let file = cm.lookup_char_pos(sp.lo()).file;
if file.name.is_macros() {
None
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} else {
Some(span)
}
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} else {
None
}
);
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let error_id = (DiagnosticMessageId::StabilityId(issue), span_key, msg.clone());
let fresh = self.sess.one_time_diagnostics.borrow_mut().insert(error_id);
if fresh {
emit_feature_err(&self.sess.parse_sess, feature, span,
GateIssue::Library(Some(issue)), &msg);
}
}
EvalResult::Unmarked => {
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// The API could be uncallable for other reasons, for example when a private module
// was referenced.
self.sess.delay_span_bug(span, &format!("encountered unmarked API: {:?}", def_id));
}
}
}
}
impl Visitor<'tcx> for Checker<'tcx> {
/// Because stability levels are scoped lexically, we want to walk
/// nested items in the context of the outer item, so enable
/// deep-walking.
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::OnlyBodies(&self.tcx.hir())
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}
fn visit_item(&mut self, item: &'tcx hir::Item) {
match item.node {
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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 }
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let def_id = self.tcx.hir().local_def_id_from_hir_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.
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hir::ItemKind::Impl(.., Some(ref t), _, ref impl_item_refs) => {
if let Res::Def(DefKind::Trait, trait_did) = t.path.res {
for impl_item_ref in impl_item_refs {
let impl_item = self.tcx.hir().impl_item(impl_item_ref.id);
let trait_item_def_id = self.tcx.associated_items(trait_did)
.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 => {
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let def_id = self.tcx.hir().local_def_id_from_hir_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) {
emit_feature_err(&self.tcx.sess.parse_sess,
sym::untagged_unions, item.span, GateIssue::Language,
"unions with `Drop` implementations are unstable");
} else {
let param_env = self.tcx.param_env(def_id);
if !param_env.can_type_implement_copy(self.tcx, ty).is_ok() {
emit_feature_err(&self.tcx.sess.parse_sess,
sym::untagged_unions, item.span, GateIssue::Language,
"unions with non-`Copy` fields are unstable");
}
}
}
_ => (/* pass */)
}
intravisit::walk_item(self, item);
}
fn visit_path(&mut self, path: &'tcx hir::Path, 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)
}
}
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impl<'tcx> TyCtxt<'tcx> {
pub fn lookup_deprecation(self, id: DefId) -> Option<Deprecation> {
self.lookup_deprecation_entry(id).map(|depr| depr.attr)
}
}
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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/// 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>(tcx: TyCtxt<'tcx>) {
let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
if tcx.stability().staged_api[&LOCAL_CRATE] {
let krate = tcx.hir().krate();
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.contains(&feature) {
// Warn if the user enables a lang feature multiple times.
duplicate_feature_err(tcx.sess, span, feature);
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}
lang_features.insert(feature);
}
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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);
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);
}
}
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>(
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tcx: TyCtxt<'tcx>,
span: Span,
feature: Symbol,
since: Symbol,
) {
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tcx.lint_hir(lint::builtin::STABLE_FEATURES,
hir::CRATE_HIR_ID,
span,
&format!("the feature `{}` has been stable since {} and no longer requires \
an attribute to enable", feature, since));
}
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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}