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 dep_graph::DepNode;
  17 use session::Session;
  18 use lint;
  19 use middle::cstore::{CrateStore, LOCAL_CRATE};
  20 use middle::def::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, Deprecation, AttrMetaMethods};
  30 use util::nodemap::{DefIdMap, FnvHashSet, FnvHashMap};
  31
  32 use rustc_front::hir;
  33 use rustc_front::hir::{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     stab_map: DefIdMap<Option<&'tcx Stability>>,
  66     depr_map: DefIdMap<Option<Deprecation>>,
  67
  68     /// Maps for each crate whether it is part of the staged API.
  69     staged_api: FnvHashMap<ast::CrateNum, bool>
  70 }
  71
  72 // A private tree-walker for producing an Index.
  73 struct Annotator<'a, 'tcx: 'a> {
  74     tcx: &'a ty::ctxt<'tcx>,
  75     index: &'a mut Index<'tcx>,
  76     parent_stab: Option<&'tcx Stability>,
  77     parent_depr: Option<Deprecation>,
  78     access_levels: &'a AccessLevels,
  79     in_trait_impl: bool,
  80 }
  81
  82 impl<'a, 'tcx: 'a> Annotator<'a, 'tcx> {
  83     // Determine the stability for a node based on its attributes and inherited
  84     // stability. The stability is recorded in the index and used as the parent.
  85     fn annotate<F>(&mut self, id: NodeId, attrs: &[Attribute],
  86                    item_sp: Span, kind: AnnotationKind, visit_children: F)
  87         where F: FnOnce(&mut Annotator)
  88     {
  89         if self.index.staged_api[&LOCAL_CRATE] && self.tcx.sess.features.borrow().staged_api {
  90             debug!("annotate(id = {:?}, attrs = {:?})", id, attrs);
  91             if let Some(..) = attr::find_deprecation(self.tcx.sess.diagnostic(), attrs, item_sp) {
  92                 self.tcx.sess.span_err(item_sp, "`#[deprecated]` cannot be used in staged api, \
  93                                                  use `#[rustc_deprecated]` instead");
  94             }
  95             if let Some(mut stab) = attr::find_stability(self.tcx.sess.diagnostic(),
  96                                                          attrs, item_sp) {
  97                 // Error if prohibited, or can't inherit anything from a container
  98                 if kind == AnnotationKind::Prohibited ||
  99                    (kind == AnnotationKind::Container &&
 100                     stab.level.is_stable() &&
 101                     stab.rustc_depr.is_none()) {
 102                     self.tcx.sess.span_err(item_sp, "This stability annotation is useless");
 103                 }
 104
 105                 debug!("annotate: found {:?}", stab);
 106                 // If parent is deprecated and we're not, inherit this by merging
 107                 // deprecated_since and its reason.
 108                 if let Some(parent_stab) = self.parent_stab {
 109                     if parent_stab.rustc_depr.is_some() && stab.rustc_depr.is_none() {
 110                         stab.rustc_depr = parent_stab.rustc_depr.clone()
 111                     }
 112                 }
 113
 114                 let stab = self.tcx.intern_stability(stab);
 115
 116                 // Check if deprecated_since < stable_since. If it is,
 117                 // this is *almost surely* an accident.
 118                 if let (&Some(attr::RustcDeprecation {since: ref dep_since, ..}),
 119                         &attr::Stable {since: ref stab_since}) = (&stab.rustc_depr, &stab.level) {
 120                     // Explicit version of iter::order::lt to handle parse errors properly
 121                     for (dep_v, stab_v) in dep_since.split(".").zip(stab_since.split(".")) {
 122                         if let (Ok(dep_v), Ok(stab_v)) = (dep_v.parse::<u64>(), stab_v.parse()) {
 123                             match dep_v.cmp(&stab_v) {
 124                                 Ordering::Less => {
 125                                     self.tcx.sess.span_err(item_sp, "An API can't be stabilized \
 126                                                                      after it is deprecated");
 127                                     break
 128                                 }
 129                                 Ordering::Equal => continue,
 130                                 Ordering::Greater => break,
 131                             }
 132                         } else {
 133                             // Act like it isn't less because the question is now nonsensical,
 134                             // and this makes us not do anything else interesting.
 135                             self.tcx.sess.span_err(item_sp, "Invalid stability or deprecation \
 136                                                              version found");
 137                             break
 138                         }
 139                     }
 140                 }
 141
 142                 let def_id = self.tcx.map.local_def_id(id);
 143                 self.index.stab_map.insert(def_id, Some(stab));
 144
 145                 let orig_parent_stab = replace(&mut self.parent_stab, Some(stab));
 146                 visit_children(self);
 147                 self.parent_stab = orig_parent_stab;
 148             } else {
 149                 debug!("annotate: not found, parent = {:?}", self.parent_stab);
 150                 let mut is_error = kind == AnnotationKind::Required &&
 151                                    self.access_levels.is_reachable(id) &&
 152                                    !self.tcx.sess.opts.test;
 153                 if let Some(stab) = self.parent_stab {
 154                     if stab.level.is_unstable() {
 155                         let def_id = self.tcx.map.local_def_id(id);
 156                         self.index.stab_map.insert(def_id, Some(stab));
 157                         is_error = false;
 158                     }
 159                 }
 160                 if is_error {
 161                     self.tcx.sess.span_err(item_sp, "This node does not have \
 162                                                      a stability attribute");
 163                 }
 164                 visit_children(self);
 165             }
 166         } else {
 167             // Emit errors for non-staged-api crates.
 168             for attr in attrs {
 169                 let tag = attr.name();
 170                 if tag == "unstable" || tag == "stable" || tag == "rustc_deprecated" {
 171                     attr::mark_used(attr);
 172                     self.tcx.sess.span_err(attr.span(), "stability attributes may not be used \
 173                                                          outside of the standard library");
 174                 }
 175             }
 176
 177             if let Some(depr) = attr::find_deprecation(self.tcx.sess.diagnostic(), attrs, item_sp) {
 178                 if kind == AnnotationKind::Prohibited {
 179                     self.tcx.sess.span_err(item_sp, "This deprecation annotation is useless");
 180                 }
 181
 182                 // `Deprecation` is just two pointers, no need to intern it
 183                 let def_id = self.tcx.map.local_def_id(id);
 184                 self.index.depr_map.insert(def_id, Some(depr.clone()));
 185
 186                 let orig_parent_depr = replace(&mut self.parent_depr, Some(depr));
 187                 visit_children(self);
 188                 self.parent_depr = orig_parent_depr;
 189             } else if let Some(depr) = self.parent_depr.clone() {
 190                 let def_id = self.tcx.map.local_def_id(id);
 191                 self.index.depr_map.insert(def_id, Some(depr));
 192                 visit_children(self);
 193             } else {
 194                 visit_children(self);
 195             }
 196         }
 197     }
 198 }
 199
 200 impl<'a, 'tcx, 'v> Visitor<'v> for Annotator<'a, 'tcx> {
 201     /// Because stability levels are scoped lexically, we want to walk
 202     /// nested items in the context of the outer item, so enable
 203     /// deep-walking.
 204     fn visit_nested_item(&mut self, item: hir::ItemId) {
 205         self.visit_item(self.tcx.map.expect_item(item.id))
 206     }
 207
 208     fn visit_item(&mut self, i: &Item) {
 209         let orig_in_trait_impl = self.in_trait_impl;
 210         let mut kind = AnnotationKind::Required;
 211         match i.node {
 212             // Inherent impls and foreign modules serve only as containers for other items,
 213             // they don't have their own stability. They still can be annotated as unstable
 214             // and propagate this unstability to children, but this annotation is completely
 215             // optional. They inherit stability from their parents when unannotated.
 216             hir::ItemImpl(_, _, _, None, _, _) | hir::ItemForeignMod(..) => {
 217                 self.in_trait_impl = false;
 218                 kind = AnnotationKind::Container;
 219             }
 220             hir::ItemImpl(_, _, _, Some(_), _, _) => {
 221                 self.in_trait_impl = true;
 222             }
 223             hir::ItemStruct(ref sd, _) => {
 224                 if !sd.is_struct() {
 225                     self.annotate(sd.id(), &i.attrs, i.span, AnnotationKind::Required, |_| {})
 226                 }
 227             }
 228             _ => {}
 229         }
 230
 231         self.annotate(i.id, &i.attrs, i.span, kind, |v| {
 232             intravisit::walk_item(v, i)
 233         });
 234         self.in_trait_impl = orig_in_trait_impl;
 235     }
 236
 237     fn visit_trait_item(&mut self, ti: &hir::TraitItem) {
 238         self.annotate(ti.id, &ti.attrs, ti.span, AnnotationKind::Required, |v| {
 239             intravisit::walk_trait_item(v, ti);
 240         });
 241     }
 242
 243     fn visit_impl_item(&mut self, ii: &hir::ImplItem) {
 244         let kind = if self.in_trait_impl {
 245             AnnotationKind::Prohibited
 246         } else {
 247             AnnotationKind::Required
 248         };
 249         self.annotate(ii.id, &ii.attrs, ii.span, kind, |v| {
 250             intravisit::walk_impl_item(v, ii);
 251         });
 252     }
 253
 254     fn visit_variant(&mut self, var: &Variant, g: &'v Generics, item_id: NodeId) {
 255         self.annotate(var.node.data.id(), &var.node.attrs, var.span, AnnotationKind::Required, |v| {
 256             intravisit::walk_variant(v, var, g, item_id);
 257         })
 258     }
 259
 260     fn visit_struct_field(&mut self, s: &StructField) {
 261         self.annotate(s.node.id, &s.node.attrs, s.span, AnnotationKind::Required, |v| {
 262             intravisit::walk_struct_field(v, s);
 263         });
 264     }
 265
 266     fn visit_foreign_item(&mut self, i: &hir::ForeignItem) {
 267         self.annotate(i.id, &i.attrs, i.span, AnnotationKind::Required, |v| {
 268             intravisit::walk_foreign_item(v, i);
 269         });
 270     }
 271
 272     fn visit_macro_def(&mut self, md: &'v hir::MacroDef) {
 273         if md.imported_from.is_none() {
 274             self.annotate(md.id, &md.attrs, md.span, AnnotationKind::Required, |_| {});
 275         }
 276     }
 277 }
 278
 279 impl<'tcx> Index<'tcx> {
 280     /// Construct the stability index for a crate being compiled.
 281     pub fn build(&mut self, tcx: &ty::ctxt<'tcx>, krate: &Crate, access_levels: &AccessLevels) {
 282         let mut annotator = Annotator {
 283             tcx: tcx,
 284             index: self,
 285             parent_stab: None,
 286             parent_depr: None,
 287             access_levels: access_levels,
 288             in_trait_impl: false,
 289         };
 290         annotator.annotate(ast::CRATE_NODE_ID, &krate.attrs, krate.span, AnnotationKind::Required,
 291                            |v| intravisit::walk_crate(v, krate));
 292     }
 293
 294     pub fn new(krate: &Crate) -> Index<'tcx> {
 295         let mut is_staged_api = false;
 296         for attr in &krate.attrs {
 297             if attr.name() == "stable" || attr.name() == "unstable" {
 298                 is_staged_api = true;
 299                 break
 300             }
 301         }
 302
 303         let mut staged_api = FnvHashMap();
 304         staged_api.insert(LOCAL_CRATE, is_staged_api);
 305         Index {
 306             staged_api: staged_api,
 307             stab_map: DefIdMap(),
 308             depr_map: DefIdMap(),
 309         }
 310     }
 311 }
 312
 313 /// Cross-references the feature names of unstable APIs with enabled
 314 /// features and possibly prints errors. Returns a list of all
 315 /// features used.
 316 pub fn check_unstable_api_usage(tcx: &ty::ctxt)
 317                                 -> FnvHashMap<InternedString, StabilityLevel> {
 318     let _task = tcx.dep_graph.in_task(DepNode::StabilityCheck);
 319     let ref active_lib_features = tcx.sess.features.borrow().declared_lib_features;
 320
 321     // Put the active features into a map for quick lookup
 322     let active_features = active_lib_features.iter().map(|&(ref s, _)| s.clone()).collect();
 323
 324     let mut checker = Checker {
 325         tcx: tcx,
 326         active_features: active_features,
 327         used_features: FnvHashMap(),
 328         in_skip_block: 0,
 329     };
 330     intravisit::walk_crate(&mut checker, tcx.map.krate());
 331
 332     checker.used_features
 333 }
 334
 335 struct Checker<'a, 'tcx: 'a> {
 336     tcx: &'a ty::ctxt<'tcx>,
 337     active_features: FnvHashSet<InternedString>,
 338     used_features: FnvHashMap<InternedString, StabilityLevel>,
 339     // Within a block where feature gate checking can be skipped.
 340     in_skip_block: u32,
 341 }
 342
 343 impl<'a, 'tcx> Checker<'a, 'tcx> {
 344     fn check(&mut self, id: DefId, span: Span,
 345              stab: &Option<&Stability>, _depr: &Option<Deprecation>) {
 346         if !is_staged_api(self.tcx, id) {
 347             return;
 348         }
 349         // Only the cross-crate scenario matters when checking unstable APIs
 350         let cross_crate = !id.is_local();
 351         if !cross_crate {
 352             return
 353         }
 354
 355         // We don't need to check for stability - presumably compiler generated code.
 356         if self.in_skip_block > 0 {
 357             return;
 358         }
 359
 360         match *stab {
 361             Some(&Stability { level: attr::Unstable {ref reason, issue}, ref feature, .. }) => {
 362                 self.used_features.insert(feature.clone(), Unstable);
 363
 364                 if !self.active_features.contains(feature) {
 365                     let msg = match *reason {
 366                         Some(ref r) => format!("use of unstable library feature '{}': {}",
 367                                                &feature, &r),
 368                         None => format!("use of unstable library feature '{}'", &feature)
 369                     };
 370                     emit_feature_err(&self.tcx.sess.parse_sess.span_diagnostic,
 371                                       &feature, span, GateIssue::Library(Some(issue)), &msg);
 372                 }
 373             }
 374             Some(&Stability { ref level, ref feature, .. }) => {
 375                 self.used_features.insert(feature.clone(), StabilityLevel::from_attr_level(level));
 376
 377                 // Stable APIs are always ok to call and deprecated APIs are
 378                 // handled by a lint.
 379             }
 380             None => {
 381                 // This is an 'unmarked' API, which should not exist
 382                 // in the standard library.
 383                 if self.tcx.sess.features.borrow().unmarked_api {
 384                     self.tcx.sess.struct_span_warn(span, "use of unmarked library feature")
 385                                  .span_note(span, "this is either a bug in the library you are \
 386                                                    using or a bug in the compiler - please \
 387                                                    report it in both places")
 388                                  .emit()
 389                 } else {
 390                     self.tcx.sess.struct_span_err(span, "use of unmarked library feature")
 391                                  .span_note(span, "this is either a bug in the library you are \
 392                                                    using or a bug in the compiler - please \
 393                                                    report it in both places")
 394                                  .span_note(span, "use #![feature(unmarked_api)] in the \
 395                                                    crate attributes to override this")
 396                                  .emit()
 397                 }
 398             }
 399         }
 400     }
 401 }
 402
 403 impl<'a, 'v, 'tcx> Visitor<'v> for Checker<'a, 'tcx> {
 404     /// Because stability levels are scoped lexically, we want to walk
 405     /// nested items in the context of the outer item, so enable
 406     /// deep-walking.
 407     fn visit_nested_item(&mut self, item: hir::ItemId) {
 408         self.visit_item(self.tcx.map.expect_item(item.id))
 409     }
 410
 411     fn visit_item(&mut self, item: &hir::Item) {
 412         // When compiling with --test we don't enforce stability on the
 413         // compiler-generated test module, demarcated with `DUMMY_SP` plus the
 414         // name `__test`
 415         if item.span == DUMMY_SP && item.name.as_str() == "__test" { return }
 416
 417         check_item(self.tcx, item, true,
 418                    &mut |id, sp, stab, depr| self.check(id, sp, stab, depr));
 419         intravisit::walk_item(self, item);
 420     }
 421
 422     fn visit_expr(&mut self, ex: &hir::Expr) {
 423         check_expr(self.tcx, ex,
 424                    &mut |id, sp, stab, depr| self.check(id, sp, stab, depr));
 425         intravisit::walk_expr(self, ex);
 426     }
 427
 428     fn visit_path(&mut self, path: &hir::Path, id: ast::NodeId) {
 429         check_path(self.tcx, path, id,
 430                    &mut |id, sp, stab, depr| self.check(id, sp, stab, depr));
 431         intravisit::walk_path(self, path)
 432     }
 433
 434     fn visit_path_list_item(&mut self, prefix: &hir::Path, item: &hir::PathListItem) {
 435         check_path_list_item(self.tcx, item,
 436                    &mut |id, sp, stab, depr| self.check(id, sp, stab, depr));
 437         intravisit::walk_path_list_item(self, prefix, item)
 438     }
 439
 440     fn visit_pat(&mut self, pat: &hir::Pat) {
 441         check_pat(self.tcx, pat,
 442                   &mut |id, sp, stab, depr| self.check(id, sp, stab, depr));
 443         intravisit::walk_pat(self, pat)
 444     }
 445
 446     fn visit_block(&mut self, b: &hir::Block) {
 447         let old_skip_count = self.in_skip_block;
 448         match b.rules {
 449             hir::BlockCheckMode::PushUnstableBlock => {
 450                 self.in_skip_block += 1;
 451             }
 452             hir::BlockCheckMode::PopUnstableBlock => {
 453                 self.in_skip_block = self.in_skip_block.checked_sub(1).unwrap();
 454             }
 455             _ => {}
 456         }
 457         intravisit::walk_block(self, b);
 458         self.in_skip_block = old_skip_count;
 459     }
 460 }
 461
 462 /// Helper for discovering nodes to check for stability
 463 pub fn check_item(tcx: &ty::ctxt, item: &hir::Item, warn_about_defns: bool,
 464                   cb: &mut FnMut(DefId, Span, &Option<&Stability>, &Option<Deprecation>)) {
 465     match item.node {
 466         hir::ItemExternCrate(_) => {
 467             // compiler-generated `extern crate` items have a dummy span.
 468             if item.span == DUMMY_SP { return }
 469
 470             let cnum = match tcx.sess.cstore.extern_mod_stmt_cnum(item.id) {
 471                 Some(cnum) => cnum,
 472                 None => return,
 473             };
 474             let id = DefId { krate: cnum, index: CRATE_DEF_INDEX };
 475             maybe_do_stability_check(tcx, id, item.span, cb);
 476         }
 477
 478         // For implementations of traits, check the stability of each item
 479         // individually as it's possible to have a stable trait with unstable
 480         // items.
 481         hir::ItemImpl(_, _, _, Some(ref t), _, ref impl_items) => {
 482             let trait_did = tcx.def_map.borrow().get(&t.ref_id).unwrap().def_id();
 483             let trait_items = tcx.trait_items(trait_did);
 484
 485             for impl_item in impl_items {
 486                 let item = trait_items.iter().find(|item| {
 487                     item.name() == impl_item.name
 488                 }).unwrap();
 489                 if warn_about_defns {
 490                     maybe_do_stability_check(tcx, item.def_id(), impl_item.span, cb);
 491                 }
 492             }
 493         }
 494
 495         _ => (/* pass */)
 496     }
 497 }
 498
 499 /// Helper for discovering nodes to check for stability
 500 pub fn check_expr(tcx: &ty::ctxt, e: &hir::Expr,
 501                   cb: &mut FnMut(DefId, Span, &Option<&Stability>, &Option<Deprecation>)) {
 502     let span;
 503     let id = match e.node {
 504         hir::ExprMethodCall(i, _, _) => {
 505             span = i.span;
 506             let method_call = ty::MethodCall::expr(e.id);
 507             tcx.tables.borrow().method_map[&method_call].def_id
 508         }
 509         hir::ExprField(ref base_e, ref field) => {
 510             span = field.span;
 511             match tcx.expr_ty_adjusted(base_e).sty {
 512                 ty::TyStruct(def, _) => def.struct_variant().field_named(field.node).did,
 513                 _ => tcx.sess.span_bug(e.span,
 514                                        "stability::check_expr: named field access on non-struct")
 515             }
 516         }
 517         hir::ExprTupField(ref base_e, ref field) => {
 518             span = field.span;
 519             match tcx.expr_ty_adjusted(base_e).sty {
 520                 ty::TyStruct(def, _) => def.struct_variant().fields[field.node].did,
 521                 ty::TyTuple(..) => return,
 522                 _ => tcx.sess.span_bug(e.span,
 523                                        "stability::check_expr: unnamed field access on \
 524                                         something other than a tuple or struct")
 525             }
 526         }
 527         hir::ExprStruct(_, ref expr_fields, _) => {
 528             let type_ = tcx.expr_ty(e);
 529             match type_.sty {
 530                 ty::TyStruct(def, _) => {
 531                     // check the stability of each field that appears
 532                     // in the construction expression.
 533                     for field in expr_fields {
 534                         let did = def.struct_variant()
 535                             .field_named(field.name.node)
 536                             .did;
 537                         maybe_do_stability_check(tcx, did, field.span, cb);
 538                     }
 539
 540                     // we're done.
 541                     return
 542                 }
 543                 // we don't look at stability attributes on
 544                 // struct-like enums (yet...), but it's definitely not
 545                 // a bug to have construct one.
 546                 ty::TyEnum(..) => return,
 547                 _ => {
 548                     tcx.sess.span_bug(e.span,
 549                                       &format!("stability::check_expr: struct construction \
 550                                                 of non-struct, type {:?}",
 551                                                type_));
 552                 }
 553             }
 554         }
 555         _ => return
 556     };
 557
 558     maybe_do_stability_check(tcx, id, span, cb);
 559 }
 560
 561 pub fn check_path(tcx: &ty::ctxt, path: &hir::Path, id: ast::NodeId,
 562                   cb: &mut FnMut(DefId, Span, &Option<&Stability>, &Option<Deprecation>)) {
 563     match tcx.def_map.borrow().get(&id).map(|d| d.full_def()) {
 564         Some(Def::PrimTy(..)) => {}
 565         Some(Def::SelfTy(..)) => {}
 566         Some(def) => {
 567             maybe_do_stability_check(tcx, def.def_id(), path.span, cb);
 568         }
 569         None => {}
 570     }
 571 }
 572
 573 pub fn check_path_list_item(tcx: &ty::ctxt, item: &hir::PathListItem,
 574                   cb: &mut FnMut(DefId, Span, &Option<&Stability>, &Option<Deprecation>)) {
 575     match tcx.def_map.borrow().get(&item.node.id()).map(|d| d.full_def()) {
 576         Some(Def::PrimTy(..)) => {}
 577         Some(def) => {
 578             maybe_do_stability_check(tcx, def.def_id(), item.span, cb);
 579         }
 580         None => {}
 581     }
 582 }
 583
 584 pub fn check_pat(tcx: &ty::ctxt, pat: &hir::Pat,
 585                  cb: &mut FnMut(DefId, Span, &Option<&Stability>, &Option<Deprecation>)) {
 586     debug!("check_pat(pat = {:?})", pat);
 587     if is_internal(tcx, pat.span) { return; }
 588
 589     let v = match tcx.pat_ty_opt(pat) {
 590         Some(&ty::TyS { sty: ty::TyStruct(def, _), .. }) => def.struct_variant(),
 591         Some(_) | None => return,
 592     };
 593     match pat.node {
 594         // Foo(a, b, c)
 595         // A Variant(..) pattern `hir::PatEnum(_, None)` doesn't have to be recursed into.
 596         hir::PatEnum(_, Some(ref pat_fields)) => {
 597             for (field, struct_field) in pat_fields.iter().zip(&v.fields) {
 598                 maybe_do_stability_check(tcx, struct_field.did, field.span, cb)
 599             }
 600         }
 601         // Foo { a, b, c }
 602         hir::PatStruct(_, ref pat_fields, _) => {
 603             for field in pat_fields {
 604                 let did = v.field_named(field.node.name).did;
 605                 maybe_do_stability_check(tcx, did, field.span, cb);
 606             }
 607         }
 608         // everything else is fine.
 609         _ => {}
 610     }
 611 }
 612
 613 fn maybe_do_stability_check(tcx: &ty::ctxt, id: DefId, span: Span,
 614                             cb: &mut FnMut(DefId, Span,
 615                                            &Option<&Stability>, &Option<Deprecation>)) {
 616     if is_internal(tcx, span) {
 617         debug!("maybe_do_stability_check: \
 618                 skipping span={:?} since it is internal", span);
 619         return;
 620     }
 621     let (stability, deprecation) = if is_staged_api(tcx, id) {
 622         (lookup_stability(tcx, id), None)
 623     } else {
 624         (None, lookup_deprecation(tcx, id))
 625     };
 626     debug!("maybe_do_stability_check: \
 627             inspecting id={:?} span={:?} of stability={:?}", id, span, stability);
 628     cb(id, span, &stability, &deprecation);
 629 }
 630
 631 fn is_internal(tcx: &ty::ctxt, span: Span) -> bool {
 632     tcx.sess.codemap().span_allows_unstable(span)
 633 }
 634
 635 fn is_staged_api(tcx: &ty::ctxt, id: DefId) -> bool {
 636     match tcx.trait_item_of_item(id) {
 637         Some(ty::MethodTraitItemId(trait_method_id))
 638             if trait_method_id != id => {
 639                 is_staged_api(tcx, trait_method_id)
 640             }
 641         _ => {
 642             *tcx.stability.borrow_mut().staged_api.entry(id.krate).or_insert_with(
 643                 || tcx.sess.cstore.is_staged_api(id.krate))
 644         }
 645     }
 646 }
 647
 648 /// Lookup the stability for a node, loading external crate
 649 /// metadata as necessary.
 650 pub fn lookup_stability<'tcx>(tcx: &ty::ctxt<'tcx>, id: DefId) -> Option<&'tcx Stability> {
 651     if let Some(st) = tcx.stability.borrow().stab_map.get(&id) {
 652         return *st;
 653     }
 654
 655     let st = lookup_stability_uncached(tcx, id);
 656     tcx.stability.borrow_mut().stab_map.insert(id, st);
 657     st
 658 }
 659
 660 pub fn lookup_deprecation<'tcx>(tcx: &ty::ctxt<'tcx>, id: DefId) -> Option<Deprecation> {
 661     if let Some(depr) = tcx.stability.borrow().depr_map.get(&id) {
 662         return depr.clone();
 663     }
 664
 665     let depr = lookup_deprecation_uncached(tcx, id);
 666     tcx.stability.borrow_mut().depr_map.insert(id, depr.clone());
 667     depr
 668 }
 669
 670 fn lookup_stability_uncached<'tcx>(tcx: &ty::ctxt<'tcx>, id: DefId) -> Option<&'tcx Stability> {
 671     debug!("lookup(id={:?})", id);
 672     if id.is_local() {
 673         None // The stability cache is filled partially lazily
 674     } else {
 675         tcx.sess.cstore.stability(id).map(|st| tcx.intern_stability(st))
 676     }
 677 }
 678
 679 fn lookup_deprecation_uncached<'tcx>(tcx: &ty::ctxt<'tcx>, id: DefId) -> Option<Deprecation> {
 680     debug!("lookup(id={:?})", id);
 681     if id.is_local() {
 682         None // The stability cache is filled partially lazily
 683     } else {
 684         tcx.sess.cstore.deprecation(id)
 685     }
 686 }
 687
 688 /// Given the list of enabled features that were not language features (i.e. that
 689 /// were expected to be library features), and the list of features used from
 690 /// libraries, identify activated features that don't exist and error about them.
 691 pub fn check_unused_or_stable_features(sess: &Session,
 692                                        lib_features_used: &FnvHashMap<InternedString,
 693                                                                       StabilityLevel>) {
 694     let ref declared_lib_features = sess.features.borrow().declared_lib_features;
 695     let mut remaining_lib_features: FnvHashMap<InternedString, Span>
 696         = declared_lib_features.clone().into_iter().collect();
 697
 698     let stable_msg = "this feature is stable. attribute no longer needed";
 699
 700     for &span in &sess.features.borrow().declared_stable_lang_features {
 701         sess.add_lint(lint::builtin::STABLE_FEATURES,
 702                       ast::CRATE_NODE_ID,
 703                       span,
 704                       stable_msg.to_string());
 705     }
 706
 707     for (used_lib_feature, level) in lib_features_used {
 708         match remaining_lib_features.remove(used_lib_feature) {
 709             Some(span) => {
 710                 if *level == Stable {
 711                     sess.add_lint(lint::builtin::STABLE_FEATURES,
 712                                   ast::CRATE_NODE_ID,
 713                                   span,
 714                                   stable_msg.to_string());
 715                 }
 716             }
 717             None => ( /* used but undeclared, handled during the previous ast visit */ )
 718         }
 719     }
 720
 721     for &span in remaining_lib_features.values() {
 722         sess.add_lint(lint::builtin::UNUSED_FEATURES,
 723                       ast::CRATE_NODE_ID,
 724                       span,
 725                       "unused or unknown feature".to_string());
 726     }
 727 }