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::intravisit::{self, Visitor, NestedVisitorMap};
  18 use rustc::infer::{InferCtxt};
  19 use rustc::ty::{self, Ty, TyCtxt, MethodCallee};
  20 use rustc::ty::adjustment;
  21 use rustc::ty::fold::{TypeFolder,TypeFoldable};
  22 use rustc::util::nodemap::DefIdSet;
  23 use syntax::ast;
  24 use syntax_pos::Span;
  25 use std::mem;
  26
  27 ///////////////////////////////////////////////////////////////////////////
  28 // Entry point
  29
  30 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
  31     pub fn resolve_type_vars_in_body(&self, body: &'gcx hir::Body)
  32                                      -> &'gcx ty::TypeckTables<'gcx> {
  33         let item_id = self.tcx.hir.body_owner(body.id());
  34         let item_def_id = self.tcx.hir.local_def_id(item_id);
  35
  36         let mut wbcx = WritebackCx::new(self, body);
  37         for arg in &body.arguments {
  38             wbcx.visit_node_id(arg.pat.span, arg.id);
  39         }
  40         wbcx.visit_body(body);
  41         wbcx.visit_upvar_borrow_map();
  42         wbcx.visit_closures();
  43         wbcx.visit_liberated_fn_sigs();
  44         wbcx.visit_fru_field_types();
  45         wbcx.visit_anon_types();
  46         wbcx.visit_cast_types();
  47         wbcx.visit_lints();
  48         wbcx.visit_free_region_map();
  49
  50         let used_trait_imports = mem::replace(&mut self.tables.borrow_mut().used_trait_imports,
  51                                               DefIdSet());
  52         debug!("used_trait_imports({:?}) = {:?}", item_def_id, used_trait_imports);
  53         wbcx.tables.used_trait_imports = used_trait_imports;
  54
  55         wbcx.tables.tainted_by_errors = self.is_tainted_by_errors();
  56
  57         self.tcx.alloc_tables(wbcx.tables)
  58     }
  59 }
  60
  61 ///////////////////////////////////////////////////////////////////////////
  62 // The Writerback context. This visitor walks the AST, checking the
  63 // fn-specific tables to find references to types or regions. It
  64 // resolves those regions to remove inference variables and writes the
  65 // final result back into the master tables in the tcx. Here and
  66 // there, it applies a few ad-hoc checks that were not convenient to
  67 // do elsewhere.
  68
  69 struct WritebackCx<'cx, 'gcx: 'cx+'tcx, 'tcx: 'cx> {
  70     fcx: &'cx FnCtxt<'cx, 'gcx, 'tcx>,
  71
  72     tables: ty::TypeckTables<'gcx>,
  73
  74     body: &'gcx hir::Body,
  75 }
  76
  77 impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
  78     fn new(fcx: &'cx FnCtxt<'cx, 'gcx, 'tcx>, body: &'gcx hir::Body)
  79         -> WritebackCx<'cx, 'gcx, 'tcx> {
  80         WritebackCx {
  81             fcx: fcx,
  82             tables: ty::TypeckTables::empty(),
  83             body: body
  84         }
  85     }
  86
  87     fn tcx(&self) -> TyCtxt<'cx, 'gcx, 'tcx> {
  88         self.fcx.tcx
  89     }
  90
  91     fn write_ty_to_tables(&mut self, node_id: ast::NodeId, ty: Ty<'gcx>) {
  92         debug!("write_ty_to_tables({}, {:?})", node_id,  ty);
  93         assert!(!ty.needs_infer());
  94         self.tables.node_types.insert(node_id, ty);
  95     }
  96
  97     // Hacky hack: During type-checking, we treat *all* operators
  98     // as potentially overloaded. But then, during writeback, if
  99     // we observe that something like `a+b` is (known to be)
 100     // operating on scalars, we clear the overload.
 101     fn fix_scalar_builtin_expr(&mut self, e: &hir::Expr) {
 102         match e.node {
 103             hir::ExprUnary(hir::UnNeg, ref inner) |
 104             hir::ExprUnary(hir::UnNot, ref inner)  => {
 105                 let inner_ty = self.fcx.node_ty(inner.id);
 106                 let inner_ty = self.fcx.resolve_type_vars_if_possible(&inner_ty);
 107
 108                 if inner_ty.is_scalar() {
 109                     self.fcx.tables.borrow_mut().method_map.remove(&e.id);
 110                 }
 111             }
 112             hir::ExprBinary(ref op, ref lhs, ref rhs) |
 113             hir::ExprAssignOp(ref op, ref lhs, ref rhs) => {
 114                 let lhs_ty = self.fcx.node_ty(lhs.id);
 115                 let lhs_ty = self.fcx.resolve_type_vars_if_possible(&lhs_ty);
 116
 117                 let rhs_ty = self.fcx.node_ty(rhs.id);
 118                 let rhs_ty = self.fcx.resolve_type_vars_if_possible(&rhs_ty);
 119
 120                 if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
 121                     self.fcx.tables.borrow_mut().method_map.remove(&e.id);
 122
 123                     // weird but true: the by-ref binops put an
 124                     // adjustment on the lhs but not the rhs; the
 125                     // adjustment for rhs is kind of baked into the
 126                     // system.
 127                     match e.node {
 128                         hir::ExprBinary(..) => {
 129                             if !op.node.is_by_value() {
 130                                 self.fcx.tables.borrow_mut().adjustments.remove(&lhs.id);
 131                             }
 132                         },
 133                         hir::ExprAssignOp(..) => {
 134                             self.fcx.tables.borrow_mut().adjustments.remove(&lhs.id);
 135                         },
 136                         _ => {},
 137                     }
 138                 }
 139             }
 140             _ => {},
 141         }
 142     }
 143 }
 144
 145 ///////////////////////////////////////////////////////////////////////////
 146 // Impl of Visitor for Resolver
 147 //
 148 // This is the master code which walks the AST. It delegates most of
 149 // the heavy lifting to the generic visit and resolve functions
 150 // below. In general, a function is made into a `visitor` if it must
 151 // traffic in node-ids or update tables in the type context etc.
 152
 153 impl<'cx, 'gcx, 'tcx> Visitor<'gcx> for WritebackCx<'cx, 'gcx, 'tcx> {
 154     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
 155         NestedVisitorMap::None
 156     }
 157
 158     fn visit_stmt(&mut self, s: &'gcx hir::Stmt) {
 159         self.visit_node_id(s.span, s.node.id());
 160         intravisit::walk_stmt(self, s);
 161     }
 162
 163     fn visit_expr(&mut self, e: &'gcx hir::Expr) {
 164         self.fix_scalar_builtin_expr(e);
 165
 166         self.visit_node_id(e.span, e.id);
 167         self.visit_method_map_entry(e.span, e.id);
 168
 169         if let hir::ExprClosure(_, _, body, _) = e.node {
 170             let body = self.fcx.tcx.hir.body(body);
 171             for arg in &body.arguments {
 172                 self.visit_node_id(e.span, arg.id);
 173             }
 174
 175             self.visit_body(body);
 176         }
 177
 178         intravisit::walk_expr(self, e);
 179     }
 180
 181     fn visit_block(&mut self, b: &'gcx hir::Block) {
 182         self.visit_node_id(b.span, b.id);
 183         intravisit::walk_block(self, b);
 184     }
 185
 186     fn visit_pat(&mut self, p: &'gcx hir::Pat) {
 187         self.visit_node_id(p.span, p.id);
 188         intravisit::walk_pat(self, p);
 189     }
 190
 191     fn visit_local(&mut self, l: &'gcx hir::Local) {
 192         intravisit::walk_local(self, l);
 193         let var_ty = self.fcx.local_ty(l.span, l.id);
 194         let var_ty = self.resolve(&var_ty, &l.span);
 195         self.write_ty_to_tables(l.id, var_ty);
 196     }
 197 }
 198
 199 impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
 200     fn visit_upvar_borrow_map(&mut self) {
 201         for (upvar_id, upvar_capture) in self.fcx.tables.borrow().upvar_capture_map.iter() {
 202             let new_upvar_capture = match *upvar_capture {
 203                 ty::UpvarCapture::ByValue => ty::UpvarCapture::ByValue,
 204                 ty::UpvarCapture::ByRef(ref upvar_borrow) => {
 205                     let r = upvar_borrow.region;
 206                     let r = self.resolve(&r, &upvar_id.var_id);
 207                     ty::UpvarCapture::ByRef(
 208                         ty::UpvarBorrow { kind: upvar_borrow.kind, region: r })
 209                 }
 210             };
 211             debug!("Upvar capture for {:?} resolved to {:?}",
 212                    upvar_id,
 213                    new_upvar_capture);
 214             self.tables.upvar_capture_map.insert(*upvar_id, new_upvar_capture);
 215         }
 216     }
 217
 218     fn visit_closures(&mut self) {
 219         for (&id, closure_ty) in self.fcx.tables.borrow().closure_tys.iter() {
 220             let closure_ty = self.resolve(closure_ty, &id);
 221             self.tables.closure_tys.insert(id, closure_ty);
 222         }
 223
 224         for (&id, &closure_kind) in self.fcx.tables.borrow().closure_kinds.iter() {
 225             self.tables.closure_kinds.insert(id, closure_kind);
 226         }
 227     }
 228
 229     fn visit_cast_types(&mut self) {
 230         self.tables.cast_kinds.extend(
 231             self.fcx.tables.borrow().cast_kinds.iter().map(|(&key, &value)| (key, value)));
 232     }
 233
 234     fn visit_lints(&mut self) {
 235         self.fcx.tables.borrow_mut().lints.transfer(&mut self.tables.lints);
 236     }
 237
 238     fn visit_free_region_map(&mut self) {
 239         let free_region_map = self.tcx().lift_to_global(&self.fcx.tables.borrow().free_region_map);
 240         let free_region_map = free_region_map.expect("all regions in free-region-map are global");
 241         self.tables.free_region_map = free_region_map;
 242     }
 243
 244     fn visit_anon_types(&mut self) {
 245         let gcx = self.tcx().global_tcx();
 246         for (&node_id, &concrete_ty) in self.fcx.anon_types.borrow().iter() {
 247             let inside_ty = self.resolve(&concrete_ty, &node_id);
 248
 249             // Convert the type from the function into a type valid outside
 250             // the function, by replacing invalid regions with 'static,
 251             // after producing an error for each of them.
 252             let outside_ty = gcx.fold_regions(&inside_ty, &mut false, |r, _| {
 253                 match *r {
 254                     // 'static and early-bound regions are valid.
 255                     ty::ReStatic |
 256                     ty::ReEarlyBound(_) |
 257                     ty::ReEmpty => r,
 258
 259                     ty::ReFree(_) |
 260                     ty::ReLateBound(..) |
 261                     ty::ReScope(_) |
 262                     ty::ReSkolemized(..) => {
 263                         let span = node_id.to_span(&self.fcx.tcx);
 264                         span_err!(self.tcx().sess, span, E0564,
 265                                   "only named lifetimes are allowed in `impl Trait`, \
 266                                    but `{}` was found in the type `{}`", r, inside_ty);
 267                         gcx.types.re_static
 268                     }
 269
 270                     ty::ReVar(_) |
 271                     ty::ReErased => {
 272                         let span = node_id.to_span(&self.fcx.tcx);
 273                         span_bug!(span, "invalid region in impl Trait: {:?}", r);
 274                     }
 275                 }
 276             });
 277
 278             self.tables.node_types.insert(node_id, outside_ty);
 279         }
 280     }
 281
 282     fn visit_node_id(&mut self, span: Span, node_id: ast::NodeId) {
 283         // Export associated path extensions.
 284         if let Some(def) = self.fcx.tables.borrow_mut().type_relative_path_defs.remove(&node_id) {
 285             self.tables.type_relative_path_defs.insert(node_id, def);
 286         }
 287
 288         // Resolve any borrowings for the node with id `node_id`
 289         self.visit_adjustments(span, node_id);
 290
 291         // Resolve the type of the node with id `node_id`
 292         let n_ty = self.fcx.node_ty(node_id);
 293         let n_ty = self.resolve(&n_ty, &span);
 294         self.write_ty_to_tables(node_id, n_ty);
 295         debug!("Node {} has type {:?}", node_id, n_ty);
 296
 297         // Resolve any substitutions
 298         if let Some(&substs) = self.fcx.tables.borrow().node_substs.get(&node_id) {
 299             let substs = self.resolve(&substs, &span);
 300             debug!("write_substs_to_tcx({}, {:?})", node_id, substs);
 301             assert!(!substs.needs_infer());
 302             self.tables.node_substs.insert(node_id, substs);
 303         }
 304     }
 305
 306     fn visit_adjustments(&mut self, span: Span, node_id: ast::NodeId) {
 307         let adjustments = self.fcx.tables.borrow_mut().adjustments.remove(&node_id);
 308         match adjustments {
 309             None => {
 310                 debug!("No adjustments for node {}", node_id);
 311             }
 312
 313             Some(adjustment) => {
 314                 let resolved_adjustment = match adjustment.kind {
 315                     adjustment::Adjust::NeverToAny => {
 316                         adjustment::Adjust::NeverToAny
 317                     }
 318
 319                     adjustment::Adjust::ReifyFnPointer => {
 320                         adjustment::Adjust::ReifyFnPointer
 321                     }
 322
 323                     adjustment::Adjust::MutToConstPointer => {
 324                         adjustment::Adjust::MutToConstPointer
 325                     }
 326
 327                     adjustment::Adjust::ClosureFnPointer => {
 328                         adjustment::Adjust::ClosureFnPointer
 329                     }
 330
 331                     adjustment::Adjust::UnsafeFnPointer => {
 332                         adjustment::Adjust::UnsafeFnPointer
 333                     }
 334
 335                     adjustment::Adjust::DerefRef { autoderefs, autoref, unsize } => {
 336                         adjustment::Adjust::DerefRef {
 337                             autoderefs: autoderefs.iter().map(|overloaded| {
 338                                 overloaded.map(|method| {
 339                                     MethodCallee {
 340                                         def_id: method.def_id,
 341                                         substs: self.resolve(&method.substs, &span),
 342                                         sig: self.resolve(&method.sig, &span),
 343                                     }
 344                                 })
 345                             }).collect(),
 346                             autoref: self.resolve(&autoref, &span),
 347                             unsize: unsize,
 348                         }
 349                     }
 350                 };
 351                 let resolved_adjustment = adjustment::Adjustment {
 352                     kind: resolved_adjustment,
 353                     target: self.resolve(&adjustment.target, &span)
 354                 };
 355                 debug!("Adjustments for node {}: {:?}", node_id, resolved_adjustment);
 356                 self.tables.adjustments.insert(node_id, resolved_adjustment);
 357             }
 358         }
 359     }
 360
 361     fn visit_method_map_entry(&mut self,
 362                               method_span: Span,
 363                               node_id: ast::NodeId) {
 364         // Resolve any method map entry
 365         let new_method = match self.fcx.tables.borrow_mut().method_map.remove(&node_id) {
 366             Some(method) => {
 367                 Some(MethodCallee {
 368                     def_id: method.def_id,
 369                     substs: self.resolve(&method.substs, &method_span),
 370                     sig: self.resolve(&method.sig, &method_span),
 371                 })
 372             }
 373             None => None
 374         };
 375
 376         //NB(jroesch): We need to match twice to avoid a double borrow which would cause an ICE
 377         if let Some(method) = new_method {
 378             self.tables.method_map.insert(node_id, method);
 379         }
 380     }
 381
 382     fn visit_liberated_fn_sigs(&mut self) {
 383         for (&node_id, fn_sig) in self.fcx.tables.borrow().liberated_fn_sigs.iter() {
 384             let fn_sig = self.resolve(fn_sig, &node_id);
 385             self.tables.liberated_fn_sigs.insert(node_id, fn_sig.clone());
 386         }
 387     }
 388
 389     fn visit_fru_field_types(&mut self) {
 390         for (&node_id, ftys) in self.fcx.tables.borrow().fru_field_types.iter() {
 391             let ftys = self.resolve(ftys, &node_id);
 392             self.tables.fru_field_types.insert(node_id, ftys);
 393         }
 394     }
 395
 396     fn resolve<T>(&self, x: &T, span: &Locatable) -> T::Lifted
 397         where T: TypeFoldable<'tcx> + ty::Lift<'gcx>
 398     {
 399         let x = x.fold_with(&mut Resolver::new(self.fcx, span, self.body));
 400         if let Some(lifted) = self.tcx().lift_to_global(&x) {
 401             lifted
 402         } else {
 403             span_bug!(span.to_span(&self.fcx.tcx),
 404                       "writeback: `{:?}` missing from the global type context",
 405                       x);
 406         }
 407     }
 408 }
 409
 410 trait Locatable {
 411     fn to_span(&self, tcx: &TyCtxt) -> Span;
 412 }
 413
 414 impl Locatable for Span {
 415     fn to_span(&self, _: &TyCtxt) -> Span { *self }
 416 }
 417
 418 impl Locatable for ast::NodeId {
 419     fn to_span(&self, tcx: &TyCtxt) -> Span { tcx.hir.span(*self) }
 420 }
 421
 422 ///////////////////////////////////////////////////////////////////////////
 423 // The Resolver. This is the type folding engine that detects
 424 // unresolved types and so forth.
 425
 426 struct Resolver<'cx, 'gcx: 'cx+'tcx, 'tcx: 'cx> {
 427     tcx: TyCtxt<'cx, 'gcx, 'tcx>,
 428     infcx: &'cx InferCtxt<'cx, 'gcx, 'tcx>,
 429     span: &'cx Locatable,
 430     body: &'gcx hir::Body,
 431 }
 432
 433 impl<'cx, 'gcx, 'tcx> Resolver<'cx, 'gcx, 'tcx> {
 434     fn new(fcx: &'cx FnCtxt<'cx, 'gcx, 'tcx>, span: &'cx Locatable, body: &'gcx hir::Body)
 435         -> Resolver<'cx, 'gcx, 'tcx>
 436     {
 437         Resolver {
 438             tcx: fcx.tcx,
 439             infcx: fcx,
 440             span: span,
 441             body: body,
 442         }
 443     }
 444
 445     fn report_error(&self, t: Ty<'tcx>) {
 446         if !self.tcx.sess.has_errors() {
 447             self.infcx.need_type_info(self.body.id(), self.span.to_span(&self.tcx), t);
 448         }
 449     }
 450 }
 451
 452 impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for Resolver<'cx, 'gcx, 'tcx> {
 453     fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx> {
 454         self.tcx
 455     }
 456
 457     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
 458         match self.infcx.fully_resolve(&t) {
 459             Ok(t) => t,
 460             Err(_) => {
 461                 debug!("Resolver::fold_ty: input type `{:?}` not fully resolvable",
 462                        t);
 463                 self.report_error(t);
 464                 self.tcx().types.err
 465             }
 466         }
 467     }
 468
 469     // FIXME This should be carefully checked
 470     // We could use `self.report_error` but it doesn't accept a ty::Region, right now.
 471     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
 472         match self.infcx.fully_resolve(&r) {
 473             Ok(r) => r,
 474             Err(_) => {
 475                 self.tcx.types.re_static
 476             }
 477         }
 478     }
 479 }
 480
 481 ///////////////////////////////////////////////////////////////////////////
 482 // During type check, we store promises with the result of trait
 483 // lookup rather than the actual results (because the results are not
 484 // necessarily available immediately). These routines unwind the
 485 // promises. It is expected that we will have already reported any
 486 // errors that may be encountered, so if the promises store an error,
 487 // a dummy result is returned.