src/librustc_typeck/check/writeback.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 // Type resolution: the phase that finds all the types in the AST with
  12 // unresolved type variables and replaces "ty_var" types with their
  13 // substitutions.
  14
  15 use check::FnCtxt;
  16 use rustc::hir;
  17 use rustc::hir::def_id::{DefId, DefIndex};
  18 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
  19 use rustc::infer::InferCtxt;
  20 use rustc::ty::{self, Ty, TyCtxt};
  21 use rustc::ty::adjustment::{Adjust, Adjustment};
  22 use rustc::ty::fold::{TypeFoldable, TypeFolder};
  23 use rustc::util::nodemap::DefIdSet;
  24 use syntax::ast;
  25 use syntax_pos::Span;
  26 use std::mem;
  27 use std::rc::Rc;
  28
  29 ///////////////////////////////////////////////////////////////////////////
  30 // Entry point
  31
  32 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
  33     pub fn resolve_type_vars_in_body(&self, body: &'gcx hir::Body) -> &'gcx ty::TypeckTables<'gcx> {
  34         let item_id = self.tcx.hir.body_owner(body.id());
  35         let item_def_id = self.tcx.hir.local_def_id(item_id);
  36
  37         let mut wbcx = WritebackCx::new(self, body);
  38         for arg in &body.arguments {
  39             wbcx.visit_node_id(arg.pat.span, arg.hir_id);
  40         }
  41         wbcx.visit_body(body);
  42         wbcx.visit_upvar_borrow_map();
  43         wbcx.visit_closures();
  44         wbcx.visit_liberated_fn_sigs();
  45         wbcx.visit_fru_field_types();
  46         wbcx.visit_anon_types();
  47         wbcx.visit_cast_types();
  48         wbcx.visit_free_region_map();
  49
  50         let used_trait_imports = mem::replace(
  51             &mut self.tables.borrow_mut().used_trait_imports,
  52             Rc::new(DefIdSet()),
  53         );
  54         debug!(
  55             "used_trait_imports({:?}) = {:?}",
  56             item_def_id,
  57             used_trait_imports
  58         );
  59         wbcx.tables.used_trait_imports = used_trait_imports;
  60
  61         wbcx.tables.tainted_by_errors = self.is_tainted_by_errors();
  62
  63         debug!(
  64             "writeback: tables for {:?} are {:#?}",
  65             item_def_id,
  66             wbcx.tables
  67         );
  68
  69         self.tcx.alloc_tables(wbcx.tables)
  70     }
  71 }
  72
  73 ///////////////////////////////////////////////////////////////////////////
  74 // The Writerback context. This visitor walks the AST, checking the
  75 // fn-specific tables to find references to types or regions. It
  76 // resolves those regions to remove inference variables and writes the
  77 // final result back into the master tables in the tcx. Here and
  78 // there, it applies a few ad-hoc checks that were not convenient to
  79 // do elsewhere.
  80
  81 struct WritebackCx<'cx, 'gcx: 'cx + 'tcx, 'tcx: 'cx> {
  82     fcx: &'cx FnCtxt<'cx, 'gcx, 'tcx>,
  83
  84     tables: ty::TypeckTables<'gcx>,
  85
  86     body: &'gcx hir::Body,
  87 }
  88
  89 impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
  90     fn new(
  91         fcx: &'cx FnCtxt<'cx, 'gcx, 'tcx>,
  92         body: &'gcx hir::Body,
  93     ) -> WritebackCx<'cx, 'gcx, 'tcx> {
  94         let owner = fcx.tcx.hir.definitions().node_to_hir_id(body.id().node_id);
  95
  96         WritebackCx {
  97             fcx,
  98             tables: ty::TypeckTables::empty(Some(DefId::local(owner.owner))),
  99             body,
 100         }
 101     }
 102
 103     fn tcx(&self) -> TyCtxt<'cx, 'gcx, 'tcx> {
 104         self.fcx.tcx
 105     }
 106
 107     fn write_ty_to_tables(&mut self, hir_id: hir::HirId, ty: Ty<'gcx>) {
 108         debug!("write_ty_to_tables({:?}, {:?})", hir_id, ty);
 109         assert!(!ty.needs_infer());
 110         self.tables.node_types_mut().insert(hir_id, ty);
 111     }
 112
 113     // Hacky hack: During type-checking, we treat *all* operators
 114     // as potentially overloaded. But then, during writeback, if
 115     // we observe that something like `a+b` is (known to be)
 116     // operating on scalars, we clear the overload.
 117     fn fix_scalar_builtin_expr(&mut self, e: &hir::Expr) {
 118         match e.node {
 119             hir::ExprUnary(hir::UnNeg, ref inner) | hir::ExprUnary(hir::UnNot, ref inner) => {
 120                 let inner_ty = self.fcx.node_ty(inner.hir_id);
 121                 let inner_ty = self.fcx.resolve_type_vars_if_possible(&inner_ty);
 122
 123                 if inner_ty.is_scalar() {
 124                     let mut tables = self.fcx.tables.borrow_mut();
 125                     tables.type_dependent_defs_mut().remove(e.hir_id);
 126                     tables.node_substs_mut().remove(e.hir_id);
 127                 }
 128             }
 129             hir::ExprBinary(ref op, ref lhs, ref rhs)
 130             | hir::ExprAssignOp(ref op, ref lhs, ref rhs) => {
 131                 let lhs_ty = self.fcx.node_ty(lhs.hir_id);
 132                 let lhs_ty = self.fcx.resolve_type_vars_if_possible(&lhs_ty);
 133
 134                 let rhs_ty = self.fcx.node_ty(rhs.hir_id);
 135                 let rhs_ty = self.fcx.resolve_type_vars_if_possible(&rhs_ty);
 136
 137                 if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
 138                     let mut tables = self.fcx.tables.borrow_mut();
 139                     tables.type_dependent_defs_mut().remove(e.hir_id);
 140                     tables.node_substs_mut().remove(e.hir_id);
 141
 142                     match e.node {
 143                         hir::ExprBinary(..) => {
 144                             if !op.node.is_by_value() {
 145                                 let mut adjustments = tables.adjustments_mut();
 146                                 adjustments.get_mut(lhs.hir_id).map(|a| a.pop());
 147                                 adjustments.get_mut(rhs.hir_id).map(|a| a.pop());
 148                             }
 149                         }
 150                         hir::ExprAssignOp(..) => {
 151                             tables
 152                                 .adjustments_mut()
 153                                 .get_mut(lhs.hir_id)
 154                                 .map(|a| a.pop());
 155                         }
 156                         _ => {}
 157                     }
 158                 }
 159             }
 160             _ => {}
 161         }
 162     }
 163
 164     // Similar to operators, indexing is always assumed to be overloaded
 165     // Here, correct cases where an indexing expression can be simplified
 166     // to use builtin indexing because the index type is known to be
 167     // usize-ish
 168     fn fix_index_builtin_expr(&mut self, e: &hir::Expr) {
 169         if let hir::ExprIndex(ref base, ref index) = e.node {
 170             let mut tables = self.fcx.tables.borrow_mut();
 171
 172             match tables.expr_ty_adjusted(&base).sty {
 173                 // All valid indexing looks like this
 174                 ty::TyRef(_, ty::TypeAndMut { ty: ref base_ty, .. }) => {
 175                     let index_ty = tables.expr_ty_adjusted(&index);
 176                     let index_ty = self.fcx.resolve_type_vars_if_possible(&index_ty);
 177
 178                     if base_ty.builtin_index().is_some()
 179                         && index_ty == self.fcx.tcx.types.usize {
 180                         // Remove the method call record
 181                         tables.type_dependent_defs_mut().remove(e.hir_id);
 182                         tables.node_substs_mut().remove(e.hir_id);
 183
 184                         tables.adjustments_mut().get_mut(base.hir_id).map(|a| {
 185                             // Discard the need for a mutable borrow
 186                             match a.pop() {
 187                                 // Extra adjustment made when indexing causes a drop
 188                                 // of size information - we need to get rid of it
 189                                 // Since this is "after" the other adjustment to be
 190                                 // discarded, we do an extra `pop()`
 191                                 Some(Adjustment { kind: Adjust::Unsize, .. }) => {
 192                                     // So the borrow discard actually happens here
 193                                     a.pop();
 194                                 },
 195                                 _ => {}
 196                             }
 197                         });
 198                     }
 199                 },
 200                 // Might encounter non-valid indexes at this point, so there
 201                 // has to be a fall-through
 202                 _ => {},
 203             }
 204         }
 205     }
 206 }
 207
 208
 209 ///////////////////////////////////////////////////////////////////////////
 210 // Impl of Visitor for Resolver
 211 //
 212 // This is the master code which walks the AST. It delegates most of
 213 // the heavy lifting to the generic visit and resolve functions
 214 // below. In general, a function is made into a `visitor` if it must
 215 // traffic in node-ids or update tables in the type context etc.
 216
 217 impl<'cx, 'gcx, 'tcx> Visitor<'gcx> for WritebackCx<'cx, 'gcx, 'tcx> {
 218     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
 219         NestedVisitorMap::None
 220     }
 221
 222     fn visit_expr(&mut self, e: &'gcx hir::Expr) {
 223         self.fix_scalar_builtin_expr(e);
 224         self.fix_index_builtin_expr(e);
 225
 226         self.visit_node_id(e.span, e.hir_id);
 227
 228         if let hir::ExprClosure(_, _, body, _, _) = e.node {
 229             let body = self.fcx.tcx.hir.body(body);
 230             for arg in &body.arguments {
 231                 self.visit_node_id(e.span, arg.hir_id);
 232             }
 233
 234             self.visit_body(body);
 235         }
 236
 237         intravisit::walk_expr(self, e);
 238     }
 239
 240     fn visit_block(&mut self, b: &'gcx hir::Block) {
 241         self.visit_node_id(b.span, b.hir_id);
 242         intravisit::walk_block(self, b);
 243     }
 244
 245     fn visit_pat(&mut self, p: &'gcx hir::Pat) {
 246         match p.node {
 247             hir::PatKind::Binding(..) => {
 248                 let bm = *self.fcx
 249                     .tables
 250                     .borrow()
 251                     .pat_binding_modes()
 252                     .get(p.hir_id)
 253                     .expect("missing binding mode");
 254                 self.tables.pat_binding_modes_mut().insert(p.hir_id, bm);
 255             }
 256             _ => {}
 257         };
 258
 259         self.visit_pat_adjustments(p.span, p.hir_id);
 260
 261         self.visit_node_id(p.span, p.hir_id);
 262         intravisit::walk_pat(self, p);
 263     }
 264
 265     fn visit_local(&mut self, l: &'gcx hir::Local) {
 266         intravisit::walk_local(self, l);
 267         let var_ty = self.fcx.local_ty(l.span, l.id);
 268         let var_ty = self.resolve(&var_ty, &l.span);
 269         self.write_ty_to_tables(l.hir_id, var_ty);
 270     }
 271
 272     fn visit_ty(&mut self, hir_ty: &'gcx hir::Ty) {
 273         intravisit::walk_ty(self, hir_ty);
 274         let ty = self.fcx.node_ty(hir_ty.hir_id);
 275         let ty = self.resolve(&ty, &hir_ty.span);
 276         self.write_ty_to_tables(hir_ty.hir_id, ty);
 277     }
 278 }
 279
 280 impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
 281     fn visit_upvar_borrow_map(&mut self) {
 282         for (upvar_id, upvar_capture) in self.fcx.tables.borrow().upvar_capture_map.iter() {
 283             let new_upvar_capture = match *upvar_capture {
 284                 ty::UpvarCapture::ByValue => ty::UpvarCapture::ByValue,
 285                 ty::UpvarCapture::ByRef(ref upvar_borrow) => {
 286                     let r = upvar_borrow.region;
 287                     let r = self.resolve(&r, &upvar_id.var_id);
 288                     ty::UpvarCapture::ByRef(ty::UpvarBorrow {
 289                         kind: upvar_borrow.kind,
 290                         region: r,
 291                     })
 292                 }
 293             };
 294             debug!(
 295                 "Upvar capture for {:?} resolved to {:?}",
 296                 upvar_id,
 297                 new_upvar_capture
 298             );
 299             self.tables
 300                 .upvar_capture_map
 301                 .insert(*upvar_id, new_upvar_capture);
 302         }
 303     }
 304
 305     fn visit_closures(&mut self) {
 306         let fcx_tables = self.fcx.tables.borrow();
 307         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 308         let common_local_id_root = fcx_tables.local_id_root.unwrap();
 309
 310         for (&id, &origin) in fcx_tables.closure_kind_origins().iter() {
 311             let hir_id = hir::HirId {
 312                 owner: common_local_id_root.index,
 313                 local_id: id,
 314             };
 315             self.tables
 316                 .closure_kind_origins_mut()
 317                 .insert(hir_id, origin);
 318         }
 319     }
 320
 321     fn visit_cast_types(&mut self) {
 322         let fcx_tables = self.fcx.tables.borrow();
 323         let fcx_cast_kinds = fcx_tables.cast_kinds();
 324         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 325         let mut self_cast_kinds = self.tables.cast_kinds_mut();
 326         let common_local_id_root = fcx_tables.local_id_root.unwrap();
 327
 328         for (&local_id, &cast_kind) in fcx_cast_kinds.iter() {
 329             let hir_id = hir::HirId {
 330                 owner: common_local_id_root.index,
 331                 local_id,
 332             };
 333             self_cast_kinds.insert(hir_id, cast_kind);
 334         }
 335     }
 336
 337     fn visit_free_region_map(&mut self) {
 338         let free_region_map = self.tcx()
 339             .lift_to_global(&self.fcx.tables.borrow().free_region_map);
 340         let free_region_map = free_region_map.expect("all regions in free-region-map are global");
 341         self.tables.free_region_map = free_region_map;
 342     }
 343
 344     fn visit_anon_types(&mut self) {
 345         let gcx = self.tcx().global_tcx();
 346         for (&def_id, anon_defn) in self.fcx.anon_types.borrow().iter() {
 347             let node_id = gcx.hir.as_local_node_id(def_id).unwrap();
 348             let instantiated_ty = self.resolve(&anon_defn.concrete_ty, &node_id);
 349             let definition_ty = self.fcx.infer_anon_definition_from_instantiation(
 350                 def_id,
 351                 anon_defn,
 352                 instantiated_ty,
 353             );
 354             let hir_id = self.tcx().hir.node_to_hir_id(node_id);
 355             self.tables.node_types_mut().insert(hir_id, definition_ty);
 356         }
 357     }
 358
 359     fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) {
 360         // Export associated path extensions and method resultions.
 361         if let Some(def) = self.fcx
 362             .tables
 363             .borrow_mut()
 364             .type_dependent_defs_mut()
 365             .remove(hir_id)
 366         {
 367             self.tables.type_dependent_defs_mut().insert(hir_id, def);
 368         }
 369
 370         // Resolve any borrowings for the node with id `node_id`
 371         self.visit_adjustments(span, hir_id);
 372
 373         // Resolve the type of the node with id `node_id`
 374         let n_ty = self.fcx.node_ty(hir_id);
 375         let n_ty = self.resolve(&n_ty, &span);
 376         self.write_ty_to_tables(hir_id, n_ty);
 377         debug!("Node {:?} has type {:?}", hir_id, n_ty);
 378
 379         // Resolve any substitutions
 380         if let Some(substs) = self.fcx.tables.borrow().node_substs_opt(hir_id) {
 381             let substs = self.resolve(&substs, &span);
 382             debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
 383             assert!(!substs.needs_infer());
 384             self.tables.node_substs_mut().insert(hir_id, substs);
 385         }
 386     }
 387
 388     fn visit_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 389         let adjustment = self.fcx
 390             .tables
 391             .borrow_mut()
 392             .adjustments_mut()
 393             .remove(hir_id);
 394         match adjustment {
 395             None => {
 396                 debug!("No adjustments for node {:?}", hir_id);
 397             }
 398
 399             Some(adjustment) => {
 400                 let resolved_adjustment = self.resolve(&adjustment, &span);
 401                 debug!(
 402                     "Adjustments for node {:?}: {:?}",
 403                     hir_id,
 404                     resolved_adjustment
 405                 );
 406                 self.tables
 407                     .adjustments_mut()
 408                     .insert(hir_id, resolved_adjustment);
 409             }
 410         }
 411     }
 412
 413     fn visit_pat_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
 414         let adjustment = self.fcx
 415             .tables
 416             .borrow_mut()
 417             .pat_adjustments_mut()
 418             .remove(hir_id);
 419         match adjustment {
 420             None => {
 421                 debug!("No pat_adjustments for node {:?}", hir_id);
 422             }
 423
 424             Some(adjustment) => {
 425                 let resolved_adjustment = self.resolve(&adjustment, &span);
 426                 debug!(
 427                     "pat_adjustments for node {:?}: {:?}",
 428                     hir_id,
 429                     resolved_adjustment
 430                 );
 431                 self.tables
 432                     .pat_adjustments_mut()
 433                     .insert(hir_id, resolved_adjustment);
 434             }
 435         }
 436     }
 437
 438     fn visit_liberated_fn_sigs(&mut self) {
 439         let fcx_tables = self.fcx.tables.borrow();
 440         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 441         let common_local_id_root = fcx_tables.local_id_root.unwrap();
 442
 443         for (&local_id, fn_sig) in fcx_tables.liberated_fn_sigs().iter() {
 444             let hir_id = hir::HirId {
 445                 owner: common_local_id_root.index,
 446                 local_id,
 447             };
 448             let fn_sig = self.resolve(fn_sig, &hir_id);
 449             self.tables
 450                 .liberated_fn_sigs_mut()
 451                 .insert(hir_id, fn_sig.clone());
 452         }
 453     }
 454
 455     fn visit_fru_field_types(&mut self) {
 456         let fcx_tables = self.fcx.tables.borrow();
 457         debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
 458         let common_local_id_root = fcx_tables.local_id_root.unwrap();
 459
 460         for (&local_id, ftys) in fcx_tables.fru_field_types().iter() {
 461             let hir_id = hir::HirId {
 462                 owner: common_local_id_root.index,
 463                 local_id,
 464             };
 465             let ftys = self.resolve(ftys, &hir_id);
 466             self.tables.fru_field_types_mut().insert(hir_id, ftys);
 467         }
 468     }
 469
 470     fn resolve<T>(&self, x: &T, span: &Locatable) -> T::Lifted
 471     where
 472         T: TypeFoldable<'tcx> + ty::Lift<'gcx>,
 473     {
 474         let x = x.fold_with(&mut Resolver::new(self.fcx, span, self.body));
 475         if let Some(lifted) = self.tcx().lift_to_global(&x) {
 476             lifted
 477         } else {
 478             span_bug!(
 479                 span.to_span(&self.fcx.tcx),
 480                 "writeback: `{:?}` missing from the global type context",
 481                 x
 482             );
 483         }
 484     }
 485 }
 486
 487 trait Locatable {
 488     fn to_span(&self, tcx: &TyCtxt) -> Span;
 489 }
 490
 491 impl Locatable for Span {
 492     fn to_span(&self, _: &TyCtxt) -> Span {
 493         *self
 494     }
 495 }
 496
 497 impl Locatable for ast::NodeId {
 498     fn to_span(&self, tcx: &TyCtxt) -> Span {
 499         tcx.hir.span(*self)
 500     }
 501 }
 502
 503 impl Locatable for DefIndex {
 504     fn to_span(&self, tcx: &TyCtxt) -> Span {
 505         let node_id = tcx.hir.def_index_to_node_id(*self);
 506         tcx.hir.span(node_id)
 507     }
 508 }
 509
 510 impl Locatable for hir::HirId {
 511     fn to_span(&self, tcx: &TyCtxt) -> Span {
 512         let node_id = tcx.hir.definitions().find_node_for_hir_id(*self);
 513         tcx.hir.span(node_id)
 514     }
 515 }
 516
 517 ///////////////////////////////////////////////////////////////////////////
 518 // The Resolver. This is the type folding engine that detects
 519 // unresolved types and so forth.
 520
 521 struct Resolver<'cx, 'gcx: 'cx + 'tcx, 'tcx: 'cx> {
 522     tcx: TyCtxt<'cx, 'gcx, 'tcx>,
 523     infcx: &'cx InferCtxt<'cx, 'gcx, 'tcx>,
 524     span: &'cx Locatable,
 525     body: &'gcx hir::Body,
 526 }
 527
 528 impl<'cx, 'gcx, 'tcx> Resolver<'cx, 'gcx, 'tcx> {
 529     fn new(
 530         fcx: &'cx FnCtxt<'cx, 'gcx, 'tcx>,
 531         span: &'cx Locatable,
 532         body: &'gcx hir::Body,
 533     ) -> Resolver<'cx, 'gcx, 'tcx> {
 534         Resolver {
 535             tcx: fcx.tcx,
 536             infcx: fcx,
 537             span,
 538             body,
 539         }
 540     }
 541
 542     fn report_error(&self, t: Ty<'tcx>) {
 543         if !self.tcx.sess.has_errors() {
 544             self.infcx
 545                 .need_type_info(Some(self.body.id()), self.span.to_span(&self.tcx), t);
 546         }
 547     }
 548 }
 549
 550 impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for Resolver<'cx, 'gcx, 'tcx> {
 551     fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx> {
 552         self.tcx
 553     }
 554
 555     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
 556         match self.infcx.fully_resolve(&t) {
 557             Ok(t) => t,
 558             Err(_) => {
 559                 debug!(
 560                     "Resolver::fold_ty: input type `{:?}` not fully resolvable",
 561                     t
 562                 );
 563                 self.report_error(t);
 564                 self.tcx().types.err
 565             }
 566         }
 567     }
 568
 569     // FIXME This should be carefully checked
 570     // We could use `self.report_error` but it doesn't accept a ty::Region, right now.
 571     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 572         match self.infcx.fully_resolve(&r) {
 573             Ok(r) => r,
 574             Err(_) => self.tcx.types.re_static,
 575         }
 576     }
 577 }
 578
 579 ///////////////////////////////////////////////////////////////////////////
 580 // During type check, we store promises with the result of trait
 581 // lookup rather than the actual results (because the results are not
 582 // necessarily available immediately). These routines unwind the
 583 // promises. It is expected that we will have already reported any
 584 // errors that may be encountered, so if the promises store an error,
 585 // a dummy result is returned.