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 use self::ResolveReason::*;
  15
  16 use astconv::AstConv;
  17 use check::FnCtxt;
  18 use middle::def_id::DefId;
  19 use middle::pat_util;
  20 use middle::ty::{self, Ty, MethodCall, MethodCallee, HasTypeFlags};
  21 use middle::ty::adjustment;
  22 use middle::ty::fold::{TypeFolder,TypeFoldable};
  23 use middle::infer;
  24 use write_substs_to_tcx;
  25 use write_ty_to_tcx;
  26
  27 use std::cell::Cell;
  28
  29 use syntax::ast;
  30 use syntax::codemap::{DUMMY_SP, Span};
  31 use rustc_front::print::pprust::pat_to_string;
  32 use rustc_front::visit;
  33 use rustc_front::visit::Visitor;
  34 use rustc_front::util as hir_util;
  35 use rustc_front::hir;
  36
  37 ///////////////////////////////////////////////////////////////////////////
  38 // Entry point functions
  39
  40 pub fn resolve_type_vars_in_expr(fcx: &FnCtxt, e: &hir::Expr) {
  41     assert_eq!(fcx.writeback_errors.get(), false);
  42     let mut wbcx = WritebackCx::new(fcx);
  43     wbcx.visit_expr(e);
  44     wbcx.visit_upvar_borrow_map();
  45     wbcx.visit_closures();
  46 }
  47
  48 pub fn resolve_type_vars_in_fn(fcx: &FnCtxt,
  49                                decl: &hir::FnDecl,
  50                                blk: &hir::Block) {
  51     assert_eq!(fcx.writeback_errors.get(), false);
  52     let mut wbcx = WritebackCx::new(fcx);
  53     wbcx.visit_block(blk);
  54     for arg in &decl.inputs {
  55         wbcx.visit_node_id(ResolvingPattern(arg.pat.span), arg.id);
  56         wbcx.visit_pat(&*arg.pat);
  57
  58         // Privacy needs the type for the whole pattern, not just each binding
  59         if !pat_util::pat_is_binding(&fcx.tcx().def_map, &*arg.pat) {
  60             wbcx.visit_node_id(ResolvingPattern(arg.pat.span),
  61                                arg.pat.id);
  62         }
  63     }
  64     wbcx.visit_upvar_borrow_map();
  65     wbcx.visit_closures();
  66 }
  67
  68 ///////////////////////////////////////////////////////////////////////////
  69 // The Writerback context. This visitor walks the AST, checking the
  70 // fn-specific tables to find references to types or regions. It
  71 // resolves those regions to remove inference variables and writes the
  72 // final result back into the master tables in the tcx. Here and
  73 // there, it applies a few ad-hoc checks that were not convenient to
  74 // do elsewhere.
  75
  76 struct WritebackCx<'cx, 'tcx: 'cx> {
  77     fcx: &'cx FnCtxt<'cx, 'tcx>,
  78 }
  79
  80 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
  81     fn new(fcx: &'cx FnCtxt<'cx, 'tcx>) -> WritebackCx<'cx, 'tcx> {
  82         WritebackCx { fcx: fcx }
  83     }
  84
  85     fn tcx(&self) -> &'cx ty::ctxt<'tcx> {
  86         self.fcx.tcx()
  87     }
  88
  89     // Hacky hack: During type-checking, we treat *all* operators
  90     // as potentially overloaded. But then, during writeback, if
  91     // we observe that something like `a+b` is (known to be)
  92     // operating on scalars, we clear the overload.
  93     fn fix_scalar_binary_expr(&mut self, e: &hir::Expr) {
  94         match e.node {
  95             hir::ExprBinary(ref op, ref lhs, ref rhs) |
  96             hir::ExprAssignOp(ref op, ref lhs, ref rhs) => {
  97                 let lhs_ty = self.fcx.node_ty(lhs.id);
  98                 let lhs_ty = self.fcx.infcx().resolve_type_vars_if_possible(&lhs_ty);
  99
 100                 let rhs_ty = self.fcx.node_ty(rhs.id);
 101                 let rhs_ty = self.fcx.infcx().resolve_type_vars_if_possible(&rhs_ty);
 102
 103                 if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
 104                     self.fcx.inh.tables.borrow_mut().method_map.remove(&MethodCall::expr(e.id));
 105
 106                     // weird but true: the by-ref binops put an
 107                     // adjustment on the lhs but not the rhs; the
 108                     // adjustment for rhs is kind of baked into the
 109                     // system.
 110                     match e.node {
 111                         hir::ExprBinary(..) => {
 112                             if !hir_util::is_by_value_binop(op.node) {
 113                                 self.fcx.inh.tables.borrow_mut().adjustments.remove(&lhs.id);
 114                             }
 115                         },
 116                         hir::ExprAssignOp(..) => {
 117                             self.fcx.inh.tables.borrow_mut().adjustments.remove(&lhs.id);
 118                         },
 119                         _ => {},
 120                     }
 121                 } else {
 122                     let tcx = self.tcx();
 123
 124                     if let hir::ExprAssignOp(..) = e.node {
 125                         if
 126                             !tcx.sess.features.borrow().augmented_assignments &&
 127                             !self.fcx.expr_ty(e).references_error()
 128                         {
 129                             tcx.sess.span_err(
 130                                 e.span,
 131                                 "overloaded augmented assignments are not stable");
 132                             fileline_help!(
 133                                 tcx.sess, e.span,
 134                                 "add #![feature(augmented_assignments)] to the crate features \
 135                                  to enable");
 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, 'tcx, 'v> Visitor<'v> for WritebackCx<'cx, 'tcx> {
 154     fn visit_item(&mut self, _: &hir::Item) {
 155         // Ignore items
 156     }
 157
 158     fn visit_stmt(&mut self, s: &hir::Stmt) {
 159         if self.fcx.writeback_errors.get() {
 160             return;
 161         }
 162
 163         self.visit_node_id(ResolvingExpr(s.span), hir_util::stmt_id(s));
 164         visit::walk_stmt(self, s);
 165     }
 166
 167     fn visit_expr(&mut self, e: &hir::Expr) {
 168         if self.fcx.writeback_errors.get() {
 169             return;
 170         }
 171
 172         self.fix_scalar_binary_expr(e);
 173
 174         self.visit_node_id(ResolvingExpr(e.span), e.id);
 175         self.visit_method_map_entry(ResolvingExpr(e.span),
 176                                     MethodCall::expr(e.id));
 177
 178         if let hir::ExprClosure(_, ref decl, _) = e.node {
 179             for input in &decl.inputs {
 180                 self.visit_node_id(ResolvingExpr(e.span), input.id);
 181             }
 182         }
 183
 184         visit::walk_expr(self, e);
 185     }
 186
 187     fn visit_block(&mut self, b: &hir::Block) {
 188         if self.fcx.writeback_errors.get() {
 189             return;
 190         }
 191
 192         self.visit_node_id(ResolvingExpr(b.span), b.id);
 193         visit::walk_block(self, b);
 194     }
 195
 196     fn visit_pat(&mut self, p: &hir::Pat) {
 197         if self.fcx.writeback_errors.get() {
 198             return;
 199         }
 200
 201         self.visit_node_id(ResolvingPattern(p.span), p.id);
 202
 203         debug!("Type for pattern binding {} (id {}) resolved to {:?}",
 204                pat_to_string(p),
 205                p.id,
 206                self.tcx().node_id_to_type(p.id));
 207
 208         visit::walk_pat(self, p);
 209     }
 210
 211     fn visit_local(&mut self, l: &hir::Local) {
 212         if self.fcx.writeback_errors.get() {
 213             return;
 214         }
 215
 216         let var_ty = self.fcx.local_ty(l.span, l.id);
 217         let var_ty = self.resolve(&var_ty, ResolvingLocal(l.span));
 218         write_ty_to_tcx(self.tcx(), l.id, var_ty);
 219         visit::walk_local(self, l);
 220     }
 221
 222     fn visit_ty(&mut self, t: &hir::Ty) {
 223         match t.node {
 224             hir::TyFixedLengthVec(ref ty, ref count_expr) => {
 225                 self.visit_ty(&**ty);
 226                 write_ty_to_tcx(self.tcx(), count_expr.id, self.tcx().types.usize);
 227             }
 228             _ => visit::walk_ty(self, t)
 229         }
 230     }
 231 }
 232
 233 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 234     fn visit_upvar_borrow_map(&self) {
 235         if self.fcx.writeback_errors.get() {
 236             return;
 237         }
 238
 239         for (upvar_id, upvar_capture) in self.fcx.inh.tables.borrow().upvar_capture_map.iter() {
 240             let new_upvar_capture = match *upvar_capture {
 241                 ty::UpvarCapture::ByValue => ty::UpvarCapture::ByValue,
 242                 ty::UpvarCapture::ByRef(ref upvar_borrow) => {
 243                     let r = upvar_borrow.region;
 244                     let r = self.resolve(&r, ResolvingUpvar(*upvar_id));
 245                     ty::UpvarCapture::ByRef(
 246                         ty::UpvarBorrow { kind: upvar_borrow.kind, region: r })
 247                 }
 248             };
 249             debug!("Upvar capture for {:?} resolved to {:?}",
 250                    upvar_id,
 251                    new_upvar_capture);
 252             self.fcx.tcx()
 253                     .tables
 254                     .borrow_mut()
 255                     .upvar_capture_map
 256                     .insert(*upvar_id, new_upvar_capture);
 257         }
 258     }
 259
 260     fn visit_closures(&self) {
 261         if self.fcx.writeback_errors.get() {
 262             return
 263         }
 264
 265         for (def_id, closure_ty) in self.fcx.inh.tables.borrow().closure_tys.iter() {
 266             let closure_ty = self.resolve(closure_ty, ResolvingClosure(*def_id));
 267             self.fcx.tcx().tables.borrow_mut().closure_tys.insert(*def_id, closure_ty);
 268         }
 269
 270         for (def_id, &closure_kind) in self.fcx.inh.tables.borrow().closure_kinds.iter() {
 271             self.fcx.tcx().tables.borrow_mut().closure_kinds.insert(*def_id, closure_kind);
 272         }
 273     }
 274
 275     fn visit_node_id(&self, reason: ResolveReason, id: ast::NodeId) {
 276         // Resolve any borrowings for the node with id `id`
 277         self.visit_adjustments(reason, id);
 278
 279         // Resolve the type of the node with id `id`
 280         let n_ty = self.fcx.node_ty(id);
 281         let n_ty = self.resolve(&n_ty, reason);
 282         write_ty_to_tcx(self.tcx(), id, n_ty);
 283         debug!("Node {} has type {:?}", id, n_ty);
 284
 285         // Resolve any substitutions
 286         self.fcx.opt_node_ty_substs(id, |item_substs| {
 287             write_substs_to_tcx(self.tcx(), id,
 288                                 self.resolve(item_substs, reason));
 289         });
 290     }
 291
 292     fn visit_adjustments(&self, reason: ResolveReason, id: ast::NodeId) {
 293         let adjustments = self.fcx.inh.tables.borrow_mut().adjustments.remove(&id);
 294         match adjustments {
 295             None => {
 296                 debug!("No adjustments for node {}", id);
 297             }
 298
 299             Some(adjustment) => {
 300                 let resolved_adjustment = match adjustment {
 301                     adjustment::AdjustReifyFnPointer => {
 302                         adjustment::AdjustReifyFnPointer
 303                     }
 304
 305                     adjustment::AdjustUnsafeFnPointer => {
 306                         adjustment::AdjustUnsafeFnPointer
 307                     }
 308
 309                     adjustment::AdjustDerefRef(adj) => {
 310                         for autoderef in 0..adj.autoderefs {
 311                             let method_call = MethodCall::autoderef(id, autoderef as u32);
 312                             self.visit_method_map_entry(reason, method_call);
 313                         }
 314
 315                         adjustment::AdjustDerefRef(adjustment::AutoDerefRef {
 316                             autoderefs: adj.autoderefs,
 317                             autoref: self.resolve(&adj.autoref, reason),
 318                             unsize: self.resolve(&adj.unsize, reason),
 319                         })
 320                     }
 321                 };
 322                 debug!("Adjustments for node {}: {:?}", id, resolved_adjustment);
 323                 self.tcx().tables.borrow_mut().adjustments.insert(
 324                     id, resolved_adjustment);
 325             }
 326         }
 327     }
 328
 329     fn visit_method_map_entry(&self,
 330                               reason: ResolveReason,
 331                               method_call: MethodCall) {
 332         // Resolve any method map entry
 333         let new_method = match self.fcx.inh.tables.borrow_mut().method_map.remove(&method_call) {
 334             Some(method) => {
 335                 debug!("writeback::resolve_method_map_entry(call={:?}, entry={:?})",
 336                        method_call,
 337                        method);
 338                 let new_method = MethodCallee {
 339                     def_id: method.def_id,
 340                     ty: self.resolve(&method.ty, reason),
 341                     substs: self.tcx().mk_substs(self.resolve(method.substs, reason)),
 342                 };
 343
 344                 Some(new_method)
 345             }
 346             None => None
 347         };
 348
 349         //NB(jroesch): We need to match twice to avoid a double borrow which would cause an ICE
 350         match new_method {
 351             Some(method) => {
 352                 self.tcx().tables.borrow_mut().method_map.insert(
 353                     method_call,
 354                     method);
 355             }
 356             None => {}
 357         }
 358     }
 359
 360     fn resolve<T:TypeFoldable<'tcx>>(&self, t: &T, reason: ResolveReason) -> T {
 361         t.fold_with(&mut Resolver::new(self.fcx, reason))
 362     }
 363 }
 364
 365 ///////////////////////////////////////////////////////////////////////////
 366 // Resolution reason.
 367
 368 #[derive(Copy, Clone)]
 369 enum ResolveReason {
 370     ResolvingExpr(Span),
 371     ResolvingLocal(Span),
 372     ResolvingPattern(Span),
 373     ResolvingUpvar(ty::UpvarId),
 374     ResolvingClosure(DefId),
 375 }
 376
 377 impl ResolveReason {
 378     fn span(&self, tcx: &ty::ctxt) -> Span {
 379         match *self {
 380             ResolvingExpr(s) => s,
 381             ResolvingLocal(s) => s,
 382             ResolvingPattern(s) => s,
 383             ResolvingUpvar(upvar_id) => {
 384                 tcx.expr_span(upvar_id.closure_expr_id)
 385             }
 386             ResolvingClosure(did) => {
 387                 if did.is_local() {
 388                     tcx.expr_span(did.node)
 389                 } else {
 390                     DUMMY_SP
 391                 }
 392             }
 393         }
 394     }
 395 }
 396
 397 ///////////////////////////////////////////////////////////////////////////
 398 // The Resolver. This is the type folding engine that detects
 399 // unresolved types and so forth.
 400
 401 struct Resolver<'cx, 'tcx: 'cx> {
 402     tcx: &'cx ty::ctxt<'tcx>,
 403     infcx: &'cx infer::InferCtxt<'cx, 'tcx>,
 404     writeback_errors: &'cx Cell<bool>,
 405     reason: ResolveReason,
 406 }
 407
 408 impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
 409     fn new(fcx: &'cx FnCtxt<'cx, 'tcx>,
 410            reason: ResolveReason)
 411            -> Resolver<'cx, 'tcx>
 412     {
 413         Resolver::from_infcx(fcx.infcx(), &fcx.writeback_errors, reason)
 414     }
 415
 416     fn from_infcx(infcx: &'cx infer::InferCtxt<'cx, 'tcx>,
 417                   writeback_errors: &'cx Cell<bool>,
 418                   reason: ResolveReason)
 419                   -> Resolver<'cx, 'tcx>
 420     {
 421         Resolver { infcx: infcx,
 422                    tcx: infcx.tcx,
 423                    writeback_errors: writeback_errors,
 424                    reason: reason }
 425     }
 426
 427     fn report_error(&self, e: infer::FixupError) {
 428         self.writeback_errors.set(true);
 429         if !self.tcx.sess.has_errors() {
 430             match self.reason {
 431                 ResolvingExpr(span) => {
 432                     span_err!(self.tcx.sess, span, E0101,
 433                         "cannot determine a type for this expression: {}",
 434                         infer::fixup_err_to_string(e));
 435                 }
 436
 437                 ResolvingLocal(span) => {
 438                     span_err!(self.tcx.sess, span, E0102,
 439                         "cannot determine a type for this local variable: {}",
 440                         infer::fixup_err_to_string(e));
 441                 }
 442
 443                 ResolvingPattern(span) => {
 444                     span_err!(self.tcx.sess, span, E0103,
 445                         "cannot determine a type for this pattern binding: {}",
 446                         infer::fixup_err_to_string(e));
 447                 }
 448
 449                 ResolvingUpvar(upvar_id) => {
 450                     let span = self.reason.span(self.tcx);
 451                     span_err!(self.tcx.sess, span, E0104,
 452                         "cannot resolve lifetime for captured variable `{}`: {}",
 453                         self.tcx.local_var_name_str(upvar_id.var_id).to_string(),
 454                         infer::fixup_err_to_string(e));
 455                 }
 456
 457                 ResolvingClosure(_) => {
 458                     let span = self.reason.span(self.tcx);
 459                     span_err!(self.tcx.sess, span, E0196,
 460                               "cannot determine a type for this closure")
 461                 }
 462             }
 463         }
 464     }
 465 }
 466
 467 impl<'cx, 'tcx> TypeFolder<'tcx> for Resolver<'cx, 'tcx> {
 468     fn tcx<'a>(&'a self) -> &'a ty::ctxt<'tcx> {
 469         self.tcx
 470     }
 471
 472     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
 473         match self.infcx.fully_resolve(&t) {
 474             Ok(t) => t,
 475             Err(e) => {
 476                 debug!("Resolver::fold_ty: input type `{:?}` not fully resolvable",
 477                        t);
 478                 self.report_error(e);
 479                 self.tcx().types.err
 480             }
 481         }
 482     }
 483
 484     fn fold_region(&mut self, r: ty::Region) -> ty::Region {
 485         match self.infcx.fully_resolve(&r) {
 486             Ok(r) => r,
 487             Err(e) => {
 488                 self.report_error(e);
 489                 ty::ReStatic
 490             }
 491         }
 492     }
 493 }
 494
 495 ///////////////////////////////////////////////////////////////////////////
 496 // During type check, we store promises with the result of trait
 497 // lookup rather than the actual results (because the results are not
 498 // necessarily available immediately). These routines unwind the
 499 // promises. It is expected that we will have already reported any
 500 // errors that may be encountered, so if the promises store an error,
 501 // a dummy result is returned.