src/librustc/middle/stability.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! A pass that annotates every item and method with its stability level,
  12 //! propagating default levels lexically from parent to children ast nodes.
  13
  14 pub use self::StabilityLevel::*;
  15
  16 use session::Session;
  17 use lint;
  18 use metadata::cstore::LOCAL_CRATE;
  19 use metadata::util::CrateStore;
  20 use middle::def;
  21 use middle::def_id::{CRATE_DEF_INDEX, DefId};
  22 use middle::ty;
  23 use middle::privacy::AccessLevels;
  24 use syntax::parse::token::InternedString;
  25 use syntax::codemap::{Span, DUMMY_SP};
  26 use syntax::ast;
  27 use syntax::ast::{NodeId, Attribute};
  28 use syntax::feature_gate::{GateIssue, emit_feature_err};
  29 use syntax::attr::{self, Stability, AttrMetaMethods};
  30 use util::nodemap::{DefIdMap, FnvHashSet, FnvHashMap};
  31
  32 use rustc_front::hir;
  33 use rustc_front::hir::{Block, Crate, Item, Generics, StructField, Variant};
  34 use rustc_front::intravisit::{self, Visitor};
  35
  36 use std::mem::replace;
  37 use std::cmp::Ordering;
  38
  39 #[derive(RustcEncodable, RustcDecodable, PartialEq, PartialOrd, Clone, Copy, Debug, Eq, Hash)]
  40 pub enum StabilityLevel {
  41     Unstable,
  42     Stable,
  43 }
  44
  45 impl StabilityLevel {
  46     pub fn from_attr_level(level: &attr::StabilityLevel) -> Self {
  47         if level.is_stable() { Stable } else { Unstable }
  48     }
  49 }
  50
  51 #[derive(PartialEq)]
  52 enum AnnotationKind {
  53     // Annotation is required if not inherited from unstable parents
  54     Required,
  55     // Annotation is useless, reject it
  56     Prohibited,
  57     // Annotation itself is useless, but it can be propagated to children
  58     Container,
  59 }
  60
  61 /// A stability index, giving the stability level for items and methods.
  62 pub struct Index<'tcx> {
  63     /// This is mostly a cache, except the stabilities of local items
  64     /// are filled by the annotator.
  65     map: DefIdMap<Option<&'tcx Stability>>,
  66
  67     /// Maps for each crate whether it is part of the staged API.
  68     staged_api: FnvHashMap<ast::CrateNum, bool>
  69 }
  70
  71 // A private tree-walker for producing an Index.
  72 struct Annotator<'a, 'tcx: 'a> {
  73     tcx: &'a ty::ctxt<'tcx>,
  74     index: &'a mut Index<'tcx>,
  75     parent: Option<&'tcx Stability>,
  76     access_levels: &'a AccessLevels,
  77     in_trait_impl: bool,
  78     in_enum: bool,
  79 }
  80
  81 impl<'a, 'tcx: 'a> Annotator<'a, 'tcx> {
  82     // Determine the stability for a node based on its attributes and inherited
  83     // stability. The stability is recorded in the index and used as the parent.
  84     fn annotate<F>(&mut self, id: NodeId, attrs: &Vec<Attribute>,
  85                    item_sp: Span, kind: AnnotationKind, visit_children: F)
  86         where F: FnOnce(&mut Annotator)
  87     {
  88         if self.index.staged_api[&LOCAL_CRATE] && self.tcx.sess.features.borrow().staged_api {
  89             debug!("annotate(id = {:?}, attrs = {:?})", id, attrs);
  90             if let Some(mut stab) = attr::find_stability(self.tcx.sess.diagnostic(),
  91                                                          attrs, item_sp) {
  92                 // Error if prohibited, or can't inherit anything from a container
  93                 if kind == AnnotationKind::Prohibited ||
  94                    (kind == AnnotationKind::Container &&
  95                     stab.level.is_stable() &&
  96                     stab.depr.is_none()) {
  97                     self.tcx.sess.span_err(item_sp, "This stability annotation is useless");
  98                 }
  99
 100                 debug!("annotate: found {:?}", stab);
 101                 // If parent is deprecated and we're not, inherit this by merging
 102                 // deprecated_since and its reason.
 103                 if let Some(parent_stab) = self.parent {
 104                     if parent_stab.depr.is_some() && stab.depr.is_none() {
 105                         stab.depr = parent_stab.depr.clone()
 106                     }
 107                 }
 108
 109                 let stab = self.tcx.intern_stability(stab);
 110
 111                 // Check if deprecated_since < stable_since. If it is,
 112                 // this is *almost surely* an accident.
 113                 if let (&Some(attr::Deprecation {since: ref dep_since, ..}),
 114                         &attr::Stable {since: ref stab_since}) = (&stab.depr, &stab.level) {
 115                     // Explicit version of iter::order::lt to handle parse errors properly
 116                     for (dep_v, stab_v) in dep_since.split(".").zip(stab_since.split(".")) {
 117                         if let (Ok(dep_v), Ok(stab_v)) = (dep_v.parse::<u64>(), stab_v.parse()) {
 118                             match dep_v.cmp(&stab_v) {
 119                                 Ordering::Less => {
 120                                     self.tcx.sess.span_err(item_sp, "An API can't be stabilized \
 121                                                                      after it is deprecated");
 122                                     break
 123                                 }
 124                                 Ordering::Equal => continue,
 125                                 Ordering::Greater => break,
 126                             }
 127                         } else {
 128                             // Act like it isn't less because the question is now nonsensical,
 129                             // and this makes us not do anything else interesting.
 130                             self.tcx.sess.span_err(item_sp, "Invalid stability or deprecation \
 131                                                              version found");
 132                             break
 133                         }
 134                     }
 135                 }
 136
 137                 let def_id = self.tcx.map.local_def_id(id);
 138                 self.index.map.insert(def_id, Some(stab));
 139
 140                 let parent = replace(&mut self.parent, Some(stab));
 141                 visit_children(self);
 142                 self.parent = parent;
 143             } else {
 144                 debug!("annotate: not found, parent = {:?}", self.parent);
 145                 let mut is_error = kind == AnnotationKind::Required &&
 146                                    self.access_levels.is_reachable(id) &&
 147                                    !self.tcx.sess.opts.test;
 148                 if let Some(stab) = self.parent {
 149                     if stab.level.is_unstable() {
 150                         let def_id = self.tcx.map.local_def_id(id);
 151                         self.index.map.insert(def_id, Some(stab));
 152                         is_error = false;
 153                     }
 154                 }
 155                 if is_error {
 156                     self.tcx.sess.span_err(item_sp, "This node does not have \
 157                                                      a stability attribute");
 158                 }
 159                 visit_children(self);
 160             }
 161         } else {
 162             // Emit errors for non-staged-api crates.
 163             for attr in attrs {
 164                 let tag = attr.name();
 165                 if tag == "unstable" || tag == "stable" || tag == "rustc_deprecated" {
 166                     attr::mark_used(attr);
 167                     self.tcx.sess.span_err(attr.span(), "stability attributes may not be used \
 168                                                          outside of the standard library");
 169                 }
 170             }
 171             visit_children(self);
 172         }
 173     }
 174 }
 175
 176 impl<'a, 'tcx, 'v> Visitor<'v> for Annotator<'a, 'tcx> {
 177     /// Because stability levels are scoped lexically, we want to walk
 178     /// nested items in the context of the outer item, so enable
 179     /// deep-walking.
 180     fn visit_nested_item(&mut self, item: hir::ItemId) {
 181         self.visit_item(self.tcx.map.expect_item(item.id))
 182     }
 183
 184     fn visit_item(&mut self, i: &Item) {
 185         let orig_in_trait_impl = self.in_trait_impl;
 186         let orig_in_enum = self.in_enum;
 187         let mut kind = AnnotationKind::Required;
 188         match i.node {
 189             // Inherent impls and foreign modules serve only as containers for other items,
 190             // they don't have their own stability. They still can be annotated as unstable
 191             // and propagate this unstability to children, but this annotation is completely
 192             // optional. They inherit stability from their parents when unannotated.
 193             hir::ItemImpl(_, _, _, None, _, _) | hir::ItemForeignMod(..) => {
 194                 self.in_trait_impl = false;
 195                 kind = AnnotationKind::Container;
 196             }
 197             hir::ItemImpl(_, _, _, Some(_), _, _) => {
 198                 self.in_trait_impl = true;
 199             }
 200             hir::ItemStruct(ref sd, _) => {
 201                 self.in_enum = false;
 202                 if !sd.is_struct() {
 203                     self.annotate(sd.id(), &i.attrs, i.span, AnnotationKind::Required, |_| {})
 204                 }
 205             }
 206             hir::ItemEnum(..) => {
 207                 self.in_enum = true;
 208             }
 209             _ => {}
 210         }
 211
 212         self.annotate(i.id, &i.attrs, i.span, kind, |v| {
 213             intravisit::walk_item(v, i)
 214         });
 215         self.in_trait_impl = orig_in_trait_impl;
 216         self.in_enum = orig_in_enum;
 217     }
 218
 219     fn visit_trait_item(&mut self, ti: &hir::TraitItem) {
 220         self.annotate(ti.id, &ti.attrs, ti.span, AnnotationKind::Required, |v| {
 221             intravisit::walk_trait_item(v, ti);
 222         });
 223     }
 224
 225     fn visit_impl_item(&mut self, ii: &hir::ImplItem) {
 226         let kind = if self.in_trait_impl {
 227             AnnotationKind::Prohibited
 228         } else {
 229             AnnotationKind::Required
 230         };
 231         self.annotate(ii.id, &ii.attrs, ii.span, kind, |v| {
 232             intravisit::walk_impl_item(v, ii);
 233         });
 234     }
 235
 236     fn visit_variant(&mut self, var: &Variant, g: &'v Generics, item_id: NodeId) {
 237         self.annotate(var.node.data.id(), &var.node.attrs, var.span, AnnotationKind::Required, |v| {
 238             intravisit::walk_variant(v, var, g, item_id);
 239         })
 240     }
 241
 242     fn visit_struct_field(&mut self, s: &StructField) {
 243         // FIXME: This is temporary, can't use attributes with tuple variant fields until snapshot
 244         let kind = if self.in_enum && s.node.kind.is_unnamed() {
 245             AnnotationKind::Prohibited
 246         } else {
 247             AnnotationKind::Required
 248         };
 249         self.annotate(s.node.id, &s.node.attrs, s.span, kind, |v| {
 250             intravisit::walk_struct_field(v, s);
 251         });
 252     }
 253
 254     fn visit_foreign_item(&mut self, i: &hir::ForeignItem) {
 255         self.annotate(i.id, &i.attrs, i.span, AnnotationKind::Required, |v| {
 256             intravisit::walk_foreign_item(v, i);
 257         });
 258     }
 259
 260     fn visit_macro_def(&mut self, md: &'v hir::MacroDef) {
 261         if md.imported_from.is_none() {
 262             self.annotate(md.id, &md.attrs, md.span, AnnotationKind::Required, |_| {});
 263         }
 264     }
 265 }
 266
 267 impl<'tcx> Index<'tcx> {
 268     /// Construct the stability index for a crate being compiled.
 269     pub fn build(&mut self, tcx: &ty::ctxt<'tcx>, krate: &Crate, access_levels: &AccessLevels) {
 270         let mut annotator = Annotator {
 271             tcx: tcx,
 272             index: self,
 273             parent: None,
 274             access_levels: access_levels,
 275             in_trait_impl: false,
 276             in_enum: false,
 277         };
 278         annotator.annotate(ast::CRATE_NODE_ID, &krate.attrs, krate.span, AnnotationKind::Required,
 279                            |v| intravisit::walk_crate(v, krate));
 280     }
 281
 282     pub fn new(krate: &Crate) -> Index<'tcx> {
 283         let mut is_staged_api = false;
 284         for attr in &krate.attrs {
 285             if attr.name() == "stable" || attr.name() == "unstable" {
 286                 is_staged_api = true;
 287                 break
 288             }
 289         }
 290
 291         let mut staged_api = FnvHashMap();
 292         staged_api.insert(LOCAL_CRATE, is_staged_api);
 293         Index {
 294             staged_api: staged_api,
 295             map: DefIdMap(),
 296         }
 297     }
 298 }
 299
 300 /// Cross-references the feature names of unstable APIs with enabled
 301 /// features and possibly prints errors. Returns a list of all
 302 /// features used.
 303 pub fn check_unstable_api_usage(tcx: &ty::ctxt)
 304                                 -> FnvHashMap<InternedString, StabilityLevel> {
 305     let ref active_lib_features = tcx.sess.features.borrow().declared_lib_features;
 306
 307     // Put the active features into a map for quick lookup
 308     let active_features = active_lib_features.iter().map(|&(ref s, _)| s.clone()).collect();
 309
 310     let mut checker = Checker {
 311         tcx: tcx,
 312         active_features: active_features,
 313         used_features: FnvHashMap(),
 314         in_skip_block: 0,
 315     };
 316     intravisit::walk_crate(&mut checker, tcx.map.krate());
 317
 318     let used_features = checker.used_features;
 319     return used_features;
 320 }
 321
 322 struct Checker<'a, 'tcx: 'a> {
 323     tcx: &'a ty::ctxt<'tcx>,
 324     active_features: FnvHashSet<InternedString>,
 325     used_features: FnvHashMap<InternedString, StabilityLevel>,
 326     // Within a block where feature gate checking can be skipped.
 327     in_skip_block: u32,
 328 }
 329
 330 impl<'a, 'tcx> Checker<'a, 'tcx> {
 331     fn check(&mut self, id: DefId, span: Span, stab: &Option<&Stability>) {
 332         // Only the cross-crate scenario matters when checking unstable APIs
 333         let cross_crate = !id.is_local();
 334         if !cross_crate {
 335             return
 336         }
 337
 338         // We don't need to check for stability - presumably compiler generated code.
 339         if self.in_skip_block > 0 {
 340             return;
 341         }
 342
 343         match *stab {
 344             Some(&Stability { level: attr::Unstable {ref reason, issue}, ref feature, .. }) => {
 345                 self.used_features.insert(feature.clone(), Unstable);
 346
 347                 if !self.active_features.contains(feature) {
 348                     let msg = match *reason {
 349                         Some(ref r) => format!("use of unstable library feature '{}': {}",
 350                                                &feature, &r),
 351                         None => format!("use of unstable library feature '{}'", &feature)
 352                     };
 353                     emit_feature_err(&self.tcx.sess.parse_sess.span_diagnostic,
 354                                       &feature, span, GateIssue::Library(Some(issue)), &msg);
 355                 }
 356             }
 357             Some(&Stability { ref level, ref feature, .. }) => {
 358                 self.used_features.insert(feature.clone(), StabilityLevel::from_attr_level(level));
 359
 360                 // Stable APIs are always ok to call and deprecated APIs are
 361                 // handled by a lint.
 362             }
 363             None => {
 364                 // This is an 'unmarked' API, which should not exist
 365                 // in the standard library.
 366                 if self.tcx.sess.features.borrow().unmarked_api {
 367                     self.tcx.sess.span_warn(span, "use of unmarked library feature");
 368                     self.tcx.sess.span_note(span, "this is either a bug in the library you are \
 369                                                    using or a bug in the compiler - please \
 370                                                    report it in both places");
 371                 } else {
 372                     self.tcx.sess.span_err(span, "use of unmarked library feature");
 373                     self.tcx.sess.span_note(span, "this is either a bug in the library you are \
 374                                                    using or a bug in the compiler - please \
 375                                                    report it in both places");
 376                     self.tcx.sess.span_note(span, "use #![feature(unmarked_api)] in the \
 377                                                    crate attributes to override this");
 378                 }
 379             }
 380         }
 381     }
 382 }
 383
 384 impl<'a, 'v, 'tcx> Visitor<'v> for Checker<'a, 'tcx> {
 385     /// Because stability levels are scoped lexically, we want to walk
 386     /// nested items in the context of the outer item, so enable
 387     /// deep-walking.
 388     fn visit_nested_item(&mut self, item: hir::ItemId) {
 389         self.visit_item(self.tcx.map.expect_item(item.id))
 390     }
 391
 392     fn visit_item(&mut self, item: &hir::Item) {
 393         // When compiling with --test we don't enforce stability on the
 394         // compiler-generated test module, demarcated with `DUMMY_SP` plus the
 395         // name `__test`
 396         if item.span == DUMMY_SP && item.name.as_str() == "__test" { return }
 397
 398         check_item(self.tcx, item, true,
 399                    &mut |id, sp, stab| self.check(id, sp, stab));
 400         intravisit::walk_item(self, item);
 401     }
 402
 403     fn visit_expr(&mut self, ex: &hir::Expr) {
 404         check_expr(self.tcx, ex,
 405                    &mut |id, sp, stab| self.check(id, sp, stab));
 406         intravisit::walk_expr(self, ex);
 407     }
 408
 409     fn visit_path(&mut self, path: &hir::Path, id: ast::NodeId) {
 410         check_path(self.tcx, path, id,
 411                    &mut |id, sp, stab| self.check(id, sp, stab));
 412         intravisit::walk_path(self, path)
 413     }
 414
 415     fn visit_path_list_item(&mut self, prefix: &hir::Path, item: &hir::PathListItem) {
 416         check_path_list_item(self.tcx, item,
 417                    &mut |id, sp, stab| self.check(id, sp, stab));
 418         intravisit::walk_path_list_item(self, prefix, item)
 419     }
 420
 421     fn visit_pat(&mut self, pat: &hir::Pat) {
 422         check_pat(self.tcx, pat,
 423                   &mut |id, sp, stab| self.check(id, sp, stab));
 424         intravisit::walk_pat(self, pat)
 425     }
 426
 427     fn visit_block(&mut self, b: &hir::Block) {
 428         let old_skip_count = self.in_skip_block;
 429         match b.rules {
 430             hir::BlockCheckMode::PushUnstableBlock => {
 431                 self.in_skip_block += 1;
 432             }
 433             hir::BlockCheckMode::PopUnstableBlock => {
 434                 self.in_skip_block = self.in_skip_block.checked_sub(1).unwrap();
 435             }
 436             _ => {}
 437         }
 438         intravisit::walk_block(self, b);
 439         self.in_skip_block = old_skip_count;
 440     }
 441 }
 442
 443 /// Helper for discovering nodes to check for stability
 444 pub fn check_item(tcx: &ty::ctxt, item: &hir::Item, warn_about_defns: bool,
 445                   cb: &mut FnMut(DefId, Span, &Option<&Stability>)) {
 446     match item.node {
 447         hir::ItemExternCrate(_) => {
 448             // compiler-generated `extern crate` items have a dummy span.
 449             if item.span == DUMMY_SP { return }
 450
 451             let cnum = match tcx.sess.cstore.extern_mod_stmt_cnum(item.id) {
 452                 Some(cnum) => cnum,
 453                 None => return,
 454             };
 455             let id = DefId { krate: cnum, index: CRATE_DEF_INDEX };
 456             maybe_do_stability_check(tcx, id, item.span, cb);
 457         }
 458
 459         // For implementations of traits, check the stability of each item
 460         // individually as it's possible to have a stable trait with unstable
 461         // items.
 462         hir::ItemImpl(_, _, _, Some(ref t), _, ref impl_items) => {
 463             let trait_did = tcx.def_map.borrow().get(&t.ref_id).unwrap().def_id();
 464             let trait_items = tcx.trait_items(trait_did);
 465
 466             for impl_item in impl_items {
 467                 let item = trait_items.iter().find(|item| {
 468                     item.name() == impl_item.name
 469                 }).unwrap();
 470                 if warn_about_defns {
 471                     maybe_do_stability_check(tcx, item.def_id(), impl_item.span, cb);
 472                 }
 473             }
 474         }
 475
 476         _ => (/* pass */)
 477     }
 478 }
 479
 480 /// Helper for discovering nodes to check for stability
 481 pub fn check_expr(tcx: &ty::ctxt, e: &hir::Expr,
 482                   cb: &mut FnMut(DefId, Span, &Option<&Stability>)) {
 483     let span;
 484     let id = match e.node {
 485         hir::ExprMethodCall(i, _, _) => {
 486             span = i.span;
 487             let method_call = ty::MethodCall::expr(e.id);
 488             tcx.tables.borrow().method_map[&method_call].def_id
 489         }
 490         hir::ExprField(ref base_e, ref field) => {
 491             span = field.span;
 492             match tcx.expr_ty_adjusted(base_e).sty {
 493                 ty::TyStruct(def, _) => def.struct_variant().field_named(field.node).did,
 494                 _ => tcx.sess.span_bug(e.span,
 495                                        "stability::check_expr: named field access on non-struct")
 496             }
 497         }
 498         hir::ExprTupField(ref base_e, ref field) => {
 499             span = field.span;
 500             match tcx.expr_ty_adjusted(base_e).sty {
 501                 ty::TyStruct(def, _) => def.struct_variant().fields[field.node].did,
 502                 ty::TyTuple(..) => return,
 503                 _ => tcx.sess.span_bug(e.span,
 504                                        "stability::check_expr: unnamed field access on \
 505                                         something other than a tuple or struct")
 506             }
 507         }
 508         hir::ExprStruct(_, ref expr_fields, _) => {
 509             let type_ = tcx.expr_ty(e);
 510             match type_.sty {
 511                 ty::TyStruct(def, _) => {
 512                     // check the stability of each field that appears
 513                     // in the construction expression.
 514                     for field in expr_fields {
 515                         let did = def.struct_variant()
 516                             .field_named(field.name.node)
 517                             .did;
 518                         maybe_do_stability_check(tcx, did, field.span, cb);
 519                     }
 520
 521                     // we're done.
 522                     return
 523                 }
 524                 // we don't look at stability attributes on
 525                 // struct-like enums (yet...), but it's definitely not
 526                 // a bug to have construct one.
 527                 ty::TyEnum(..) => return,
 528                 _ => {
 529                     tcx.sess.span_bug(e.span,
 530                                       &format!("stability::check_expr: struct construction \
 531                                                 of non-struct, type {:?}",
 532                                                type_));
 533                 }
 534             }
 535         }
 536         _ => return
 537     };
 538
 539     maybe_do_stability_check(tcx, id, span, cb);
 540 }
 541
 542 pub fn check_path(tcx: &ty::ctxt, path: &hir::Path, id: ast::NodeId,
 543                   cb: &mut FnMut(DefId, Span, &Option<&Stability>)) {
 544     match tcx.def_map.borrow().get(&id).map(|d| d.full_def()) {
 545         Some(def::DefPrimTy(..)) => {}
 546         Some(def::DefSelfTy(..)) => {}
 547         Some(def) => {
 548             maybe_do_stability_check(tcx, def.def_id(), path.span, cb);
 549         }
 550         None => {}
 551     }
 552 }
 553
 554 pub fn check_path_list_item(tcx: &ty::ctxt, item: &hir::PathListItem,
 555                   cb: &mut FnMut(DefId, Span, &Option<&Stability>)) {
 556     match tcx.def_map.borrow().get(&item.node.id()).map(|d| d.full_def()) {
 557         Some(def::DefPrimTy(..)) => {}
 558         Some(def) => {
 559             maybe_do_stability_check(tcx, def.def_id(), item.span, cb);
 560         }
 561         None => {}
 562     }
 563 }
 564
 565 pub fn check_pat(tcx: &ty::ctxt, pat: &hir::Pat,
 566                  cb: &mut FnMut(DefId, Span, &Option<&Stability>)) {
 567     debug!("check_pat(pat = {:?})", pat);
 568     if is_internal(tcx, pat.span) { return; }
 569
 570     let v = match tcx.pat_ty_opt(pat) {
 571         Some(&ty::TyS { sty: ty::TyStruct(def, _), .. }) => def.struct_variant(),
 572         Some(_) | None => return,
 573     };
 574     match pat.node {
 575         // Foo(a, b, c)
 576         // A Variant(..) pattern `hir::PatEnum(_, None)` doesn't have to be recursed into.
 577         hir::PatEnum(_, Some(ref pat_fields)) => {
 578             for (field, struct_field) in pat_fields.iter().zip(&v.fields) {
 579                 maybe_do_stability_check(tcx, struct_field.did, field.span, cb)
 580             }
 581         }
 582         // Foo { a, b, c }
 583         hir::PatStruct(_, ref pat_fields, _) => {
 584             for field in pat_fields {
 585                 let did = v.field_named(field.node.name).did;
 586                 maybe_do_stability_check(tcx, did, field.span, cb);
 587             }
 588         }
 589         // everything else is fine.
 590         _ => {}
 591     }
 592 }
 593
 594 fn maybe_do_stability_check(tcx: &ty::ctxt, id: DefId, span: Span,
 595                             cb: &mut FnMut(DefId, Span, &Option<&Stability>)) {
 596     if !is_staged_api(tcx, id) {
 597         debug!("maybe_do_stability_check: \
 598                 skipping id={:?} since it is not staged_api", id);
 599         return;
 600     }
 601     if is_internal(tcx, span) {
 602         debug!("maybe_do_stability_check: \
 603                 skipping span={:?} since it is internal", span);
 604         return;
 605     }
 606     let ref stability = lookup(tcx, id);
 607     debug!("maybe_do_stability_check: \
 608             inspecting id={:?} span={:?} of stability={:?}", id, span, stability);
 609     cb(id, span, stability);
 610 }
 611
 612 fn is_internal(tcx: &ty::ctxt, span: Span) -> bool {
 613     tcx.sess.codemap().span_allows_unstable(span)
 614 }
 615
 616 fn is_staged_api(tcx: &ty::ctxt, id: DefId) -> bool {
 617     match tcx.trait_item_of_item(id) {
 618         Some(ty::MethodTraitItemId(trait_method_id))
 619             if trait_method_id != id => {
 620                 is_staged_api(tcx, trait_method_id)
 621             }
 622         _ => {
 623             *tcx.stability.borrow_mut().staged_api.entry(id.krate).or_insert_with(
 624                 || tcx.sess.cstore.is_staged_api(id.krate))
 625         }
 626     }
 627 }
 628
 629 /// Lookup the stability for a node, loading external crate
 630 /// metadata as necessary.
 631 pub fn lookup<'tcx>(tcx: &ty::ctxt<'tcx>, id: DefId) -> Option<&'tcx Stability> {
 632     if let Some(st) = tcx.stability.borrow().map.get(&id) {
 633         return *st;
 634     }
 635
 636     let st = lookup_uncached(tcx, id);
 637     tcx.stability.borrow_mut().map.insert(id, st);
 638     st
 639 }
 640
 641 fn lookup_uncached<'tcx>(tcx: &ty::ctxt<'tcx>, id: DefId) -> Option<&'tcx Stability> {
 642     debug!("lookup(id={:?})", id);
 643
 644     // is this definition the implementation of a trait method?
 645     match tcx.trait_item_of_item(id) {
 646         Some(ty::MethodTraitItemId(trait_method_id)) if trait_method_id != id => {
 647             debug!("lookup: trait_method_id={:?}", trait_method_id);
 648             return lookup(tcx, trait_method_id)
 649         }
 650         _ => {}
 651     }
 652
 653     let item_stab = if id.is_local() {
 654         None // The stability cache is filled partially lazily
 655     } else {
 656         tcx.sess.cstore.stability(id).map(|st| tcx.intern_stability(st))
 657     };
 658
 659     item_stab.or_else(|| {
 660         if tcx.is_impl(id) {
 661             if let Some(trait_id) = tcx.trait_id_of_impl(id) {
 662                 // FIXME (#18969): for the time being, simply use the
 663                 // stability of the trait to determine the stability of any
 664                 // unmarked impls for it. See FIXME above for more details.
 665
 666                 debug!("lookup: trait_id={:?}", trait_id);
 667                 return lookup(tcx, trait_id);
 668             }
 669         }
 670         None
 671     })
 672 }
 673
 674 /// Given the list of enabled features that were not language features (i.e. that
 675 /// were expected to be library features), and the list of features used from
 676 /// libraries, identify activated features that don't exist and error about them.
 677 pub fn check_unused_or_stable_features(sess: &Session,
 678                                        lib_features_used: &FnvHashMap<InternedString,
 679                                                                       StabilityLevel>) {
 680     let ref declared_lib_features = sess.features.borrow().declared_lib_features;
 681     let mut remaining_lib_features: FnvHashMap<InternedString, Span>
 682         = declared_lib_features.clone().into_iter().collect();
 683
 684     let stable_msg = "this feature is stable. attribute no longer needed";
 685
 686     for &span in &sess.features.borrow().declared_stable_lang_features {
 687         sess.add_lint(lint::builtin::STABLE_FEATURES,
 688                       ast::CRATE_NODE_ID,
 689                       span,
 690                       stable_msg.to_string());
 691     }
 692
 693     for (used_lib_feature, level) in lib_features_used {
 694         match remaining_lib_features.remove(used_lib_feature) {
 695             Some(span) => {
 696                 if *level == Stable {
 697                     sess.add_lint(lint::builtin::STABLE_FEATURES,
 698                                   ast::CRATE_NODE_ID,
 699                                   span,
 700                                   stable_msg.to_string());
 701                 }
 702             }
 703             None => ( /* used but undeclared, handled during the previous ast visit */ )
 704         }
 705     }
 706
 707     for &span in remaining_lib_features.values() {
 708         sess.add_lint(lint::builtin::UNUSED_FEATURES,
 709                       ast::CRATE_NODE_ID,
 710                       span,
 711                       "unused or unknown feature".to_string());
 712     }
 713 }