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::intravisit::{self, Visitor};
  33 use rustc_front::util as hir_util;
  34 use rustc_front::hir;
  35
  36 ///////////////////////////////////////////////////////////////////////////
  37 // Entry point functions
  38
  39 pub fn resolve_type_vars_in_expr(fcx: &FnCtxt, e: &hir::Expr) {
  40     assert_eq!(fcx.writeback_errors.get(), false);
  41     let mut wbcx = WritebackCx::new(fcx);
  42     wbcx.visit_expr(e);
  43     wbcx.visit_upvar_borrow_map();
  44     wbcx.visit_closures();
  45     wbcx.visit_liberated_fn_sigs();
  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.borrow(), &*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     wbcx.visit_liberated_fn_sigs();
  67 }
  68
  69 ///////////////////////////////////////////////////////////////////////////
  70 // The Writerback context. This visitor walks the AST, checking the
  71 // fn-specific tables to find references to types or regions. It
  72 // resolves those regions to remove inference variables and writes the
  73 // final result back into the master tables in the tcx. Here and
  74 // there, it applies a few ad-hoc checks that were not convenient to
  75 // do elsewhere.
  76
  77 struct WritebackCx<'cx, 'tcx: 'cx> {
  78     fcx: &'cx FnCtxt<'cx, 'tcx>,
  79 }
  80
  81 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
  82     fn new(fcx: &'cx FnCtxt<'cx, 'tcx>) -> WritebackCx<'cx, 'tcx> {
  83         WritebackCx { fcx: fcx }
  84     }
  85
  86     fn tcx(&self) -> &'cx ty::ctxt<'tcx> {
  87         self.fcx.tcx()
  88     }
  89
  90     // Hacky hack: During type-checking, we treat *all* operators
  91     // as potentially overloaded. But then, during writeback, if
  92     // we observe that something like `a+b` is (known to be)
  93     // operating on scalars, we clear the overload.
  94     fn fix_scalar_binary_expr(&mut self, e: &hir::Expr) {
  95         match e.node {
  96             hir::ExprBinary(ref op, ref lhs, ref rhs) |
  97             hir::ExprAssignOp(ref op, ref lhs, ref rhs) => {
  98                 let lhs_ty = self.fcx.node_ty(lhs.id);
  99                 let lhs_ty = self.fcx.infcx().resolve_type_vars_if_possible(&lhs_ty);
 100
 101                 let rhs_ty = self.fcx.node_ty(rhs.id);
 102                 let rhs_ty = self.fcx.infcx().resolve_type_vars_if_possible(&rhs_ty);
 103
 104                 if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
 105                     self.fcx.inh.tables.borrow_mut().method_map.remove(&MethodCall::expr(e.id));
 106
 107                     // weird but true: the by-ref binops put an
 108                     // adjustment on the lhs but not the rhs; the
 109                     // adjustment for rhs is kind of baked into the
 110                     // system.
 111                     match e.node {
 112                         hir::ExprBinary(..) => {
 113                             if !hir_util::is_by_value_binop(op.node) {
 114                                 self.fcx.inh.tables.borrow_mut().adjustments.remove(&lhs.id);
 115                             }
 116                         },
 117                         hir::ExprAssignOp(..) => {
 118                             self.fcx.inh.tables.borrow_mut().adjustments.remove(&lhs.id);
 119                         },
 120                         _ => {},
 121                     }
 122                 } else {
 123                     let tcx = self.tcx();
 124
 125                     if let hir::ExprAssignOp(..) = e.node {
 126                         if
 127                             !tcx.sess.features.borrow().augmented_assignments &&
 128                             !self.fcx.expr_ty(e).references_error()
 129                         {
 130                             tcx.sess.span_err(
 131                                 e.span,
 132                                 "overloaded augmented assignments are not stable");
 133                             fileline_help!(
 134                                 tcx.sess, e.span,
 135                                 "add #![feature(augmented_assignments)] to the crate root \
 136                                  to enable");
 137                         }
 138                     }
 139                 }
 140             }
 141             _ => {},
 142         }
 143     }
 144 }
 145
 146 ///////////////////////////////////////////////////////////////////////////
 147 // Impl of Visitor for Resolver
 148 //
 149 // This is the master code which walks the AST. It delegates most of
 150 // the heavy lifting to the generic visit and resolve functions
 151 // below. In general, a function is made into a `visitor` if it must
 152 // traffic in node-ids or update tables in the type context etc.
 153
 154 impl<'cx, 'tcx, 'v> Visitor<'v> for WritebackCx<'cx, 'tcx> {
 155     fn visit_stmt(&mut self, s: &hir::Stmt) {
 156         if self.fcx.writeback_errors.get() {
 157             return;
 158         }
 159
 160         self.visit_node_id(ResolvingExpr(s.span), hir_util::stmt_id(s));
 161         intravisit::walk_stmt(self, s);
 162     }
 163
 164     fn visit_expr(&mut self, e: &hir::Expr) {
 165         if self.fcx.writeback_errors.get() {
 166             return;
 167         }
 168
 169         self.fix_scalar_binary_expr(e);
 170
 171         self.visit_node_id(ResolvingExpr(e.span), e.id);
 172         self.visit_method_map_entry(ResolvingExpr(e.span),
 173                                     MethodCall::expr(e.id));
 174
 175         if let hir::ExprClosure(_, ref decl, _) = e.node {
 176             for input in &decl.inputs {
 177                 self.visit_node_id(ResolvingExpr(e.span), input.id);
 178             }
 179         }
 180
 181         intravisit::walk_expr(self, e);
 182     }
 183
 184     fn visit_block(&mut self, b: &hir::Block) {
 185         if self.fcx.writeback_errors.get() {
 186             return;
 187         }
 188
 189         self.visit_node_id(ResolvingExpr(b.span), b.id);
 190         intravisit::walk_block(self, b);
 191     }
 192
 193     fn visit_pat(&mut self, p: &hir::Pat) {
 194         if self.fcx.writeback_errors.get() {
 195             return;
 196         }
 197
 198         self.visit_node_id(ResolvingPattern(p.span), p.id);
 199
 200         debug!("Type for pattern binding {} (id {}) resolved to {:?}",
 201                pat_to_string(p),
 202                p.id,
 203                self.tcx().node_id_to_type(p.id));
 204
 205         intravisit::walk_pat(self, p);
 206     }
 207
 208     fn visit_local(&mut self, l: &hir::Local) {
 209         if self.fcx.writeback_errors.get() {
 210             return;
 211         }
 212
 213         let var_ty = self.fcx.local_ty(l.span, l.id);
 214         let var_ty = self.resolve(&var_ty, ResolvingLocal(l.span));
 215         write_ty_to_tcx(self.tcx(), l.id, var_ty);
 216         intravisit::walk_local(self, l);
 217     }
 218
 219     fn visit_ty(&mut self, t: &hir::Ty) {
 220         match t.node {
 221             hir::TyFixedLengthVec(ref ty, ref count_expr) => {
 222                 self.visit_ty(&**ty);
 223                 write_ty_to_tcx(self.tcx(), count_expr.id, self.tcx().types.usize);
 224             }
 225             hir::TyBareFn(ref function_declaration) => {
 226                 intravisit::walk_fn_decl_nopat(self, &function_declaration.decl);
 227                 walk_list!(self, visit_lifetime_def, &function_declaration.lifetimes);
 228             }
 229             _ => intravisit::walk_ty(self, t)
 230         }
 231     }
 232 }
 233
 234 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 235     fn visit_upvar_borrow_map(&self) {
 236         if self.fcx.writeback_errors.get() {
 237             return;
 238         }
 239
 240         for (upvar_id, upvar_capture) in self.fcx.inh.tables.borrow().upvar_capture_map.iter() {
 241             let new_upvar_capture = match *upvar_capture {
 242                 ty::UpvarCapture::ByValue => ty::UpvarCapture::ByValue,
 243                 ty::UpvarCapture::ByRef(ref upvar_borrow) => {
 244                     let r = upvar_borrow.region;
 245                     let r = self.resolve(&r, ResolvingUpvar(*upvar_id));
 246                     ty::UpvarCapture::ByRef(
 247                         ty::UpvarBorrow { kind: upvar_borrow.kind, region: r })
 248                 }
 249             };
 250             debug!("Upvar capture for {:?} resolved to {:?}",
 251                    upvar_id,
 252                    new_upvar_capture);
 253             self.fcx.tcx()
 254                     .tables
 255                     .borrow_mut()
 256                     .upvar_capture_map
 257                     .insert(*upvar_id, new_upvar_capture);
 258         }
 259     }
 260
 261     fn visit_closures(&self) {
 262         if self.fcx.writeback_errors.get() {
 263             return
 264         }
 265
 266         for (def_id, closure_ty) in self.fcx.inh.tables.borrow().closure_tys.iter() {
 267             let closure_ty = self.resolve(closure_ty, ResolvingClosure(*def_id));
 268             self.fcx.tcx().tables.borrow_mut().closure_tys.insert(*def_id, closure_ty);
 269         }
 270
 271         for (def_id, &closure_kind) in self.fcx.inh.tables.borrow().closure_kinds.iter() {
 272             self.fcx.tcx().tables.borrow_mut().closure_kinds.insert(*def_id, closure_kind);
 273         }
 274     }
 275
 276     fn visit_node_id(&self, reason: ResolveReason, id: ast::NodeId) {
 277         // Resolve any borrowings for the node with id `id`
 278         self.visit_adjustments(reason, id);
 279
 280         // Resolve the type of the node with id `id`
 281         let n_ty = self.fcx.node_ty(id);
 282         let n_ty = self.resolve(&n_ty, reason);
 283         write_ty_to_tcx(self.tcx(), id, n_ty);
 284         debug!("Node {} has type {:?}", id, n_ty);
 285
 286         // Resolve any substitutions
 287         self.fcx.opt_node_ty_substs(id, |item_substs| {
 288             write_substs_to_tcx(self.tcx(), id,
 289                                 self.resolve(item_substs, reason));
 290         });
 291     }
 292
 293     fn visit_adjustments(&self, reason: ResolveReason, id: ast::NodeId) {
 294         let adjustments = self.fcx.inh.tables.borrow_mut().adjustments.remove(&id);
 295         match adjustments {
 296             None => {
 297                 debug!("No adjustments for node {}", id);
 298             }
 299
 300             Some(adjustment) => {
 301                 let resolved_adjustment = match adjustment {
 302                     adjustment::AdjustReifyFnPointer => {
 303                         adjustment::AdjustReifyFnPointer
 304                     }
 305
 306                     adjustment::AdjustUnsafeFnPointer => {
 307                         adjustment::AdjustUnsafeFnPointer
 308                     }
 309
 310                     adjustment::AdjustDerefRef(adj) => {
 311                         for autoderef in 0..adj.autoderefs {
 312                             let method_call = MethodCall::autoderef(id, autoderef as u32);
 313                             self.visit_method_map_entry(reason, method_call);
 314                         }
 315
 316                         adjustment::AdjustDerefRef(adjustment::AutoDerefRef {
 317                             autoderefs: adj.autoderefs,
 318                             autoref: self.resolve(&adj.autoref, reason),
 319                             unsize: self.resolve(&adj.unsize, reason),
 320                         })
 321                     }
 322                 };
 323                 debug!("Adjustments for node {}: {:?}", id, resolved_adjustment);
 324                 self.tcx().tables.borrow_mut().adjustments.insert(
 325                     id, resolved_adjustment);
 326             }
 327         }
 328     }
 329
 330     fn visit_method_map_entry(&self,
 331                               reason: ResolveReason,
 332                               method_call: MethodCall) {
 333         // Resolve any method map entry
 334         let new_method = match self.fcx.inh.tables.borrow_mut().method_map.remove(&method_call) {
 335             Some(method) => {
 336                 debug!("writeback::resolve_method_map_entry(call={:?}, entry={:?})",
 337                        method_call,
 338                        method);
 339                 let new_method = MethodCallee {
 340                     def_id: method.def_id,
 341                     ty: self.resolve(&method.ty, reason),
 342                     substs: self.tcx().mk_substs(self.resolve(method.substs, reason)),
 343                 };
 344
 345                 Some(new_method)
 346             }
 347             None => None
 348         };
 349
 350         //NB(jroesch): We need to match twice to avoid a double borrow which would cause an ICE
 351         match new_method {
 352             Some(method) => {
 353                 self.tcx().tables.borrow_mut().method_map.insert(
 354                     method_call,
 355                     method);
 356             }
 357             None => {}
 358         }
 359     }
 360
 361     fn visit_liberated_fn_sigs(&self) {
 362         for (&node_id, fn_sig) in self.fcx.inh.tables.borrow().liberated_fn_sigs.iter() {
 363             let fn_sig = self.resolve(fn_sig, ResolvingFnSig(node_id));
 364             self.tcx().tables.borrow_mut().liberated_fn_sigs.insert(node_id, fn_sig.clone());
 365         }
 366     }
 367
 368     fn resolve<T:TypeFoldable<'tcx>>(&self, t: &T, reason: ResolveReason) -> T {
 369         t.fold_with(&mut Resolver::new(self.fcx, reason))
 370     }
 371 }
 372
 373 ///////////////////////////////////////////////////////////////////////////
 374 // Resolution reason.
 375
 376 #[derive(Copy, Clone)]
 377 enum ResolveReason {
 378     ResolvingExpr(Span),
 379     ResolvingLocal(Span),
 380     ResolvingPattern(Span),
 381     ResolvingUpvar(ty::UpvarId),
 382     ResolvingClosure(DefId),
 383     ResolvingFnSig(ast::NodeId),
 384 }
 385
 386 impl ResolveReason {
 387     fn span(&self, tcx: &ty::ctxt) -> Span {
 388         match *self {
 389             ResolvingExpr(s) => s,
 390             ResolvingLocal(s) => s,
 391             ResolvingPattern(s) => s,
 392             ResolvingUpvar(upvar_id) => {
 393                 tcx.expr_span(upvar_id.closure_expr_id)
 394             }
 395             ResolvingFnSig(id) => {
 396                 tcx.map.span(id)
 397             }
 398             ResolvingClosure(did) => {
 399                 if let Some(node_id) = tcx.map.as_local_node_id(did) {
 400                     tcx.expr_span(node_id)
 401                 } else {
 402                     DUMMY_SP
 403                 }
 404             }
 405         }
 406     }
 407 }
 408
 409 ///////////////////////////////////////////////////////////////////////////
 410 // The Resolver. This is the type folding engine that detects
 411 // unresolved types and so forth.
 412
 413 struct Resolver<'cx, 'tcx: 'cx> {
 414     tcx: &'cx ty::ctxt<'tcx>,
 415     infcx: &'cx infer::InferCtxt<'cx, 'tcx>,
 416     writeback_errors: &'cx Cell<bool>,
 417     reason: ResolveReason,
 418 }
 419
 420 impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
 421     fn new(fcx: &'cx FnCtxt<'cx, 'tcx>,
 422            reason: ResolveReason)
 423            -> Resolver<'cx, 'tcx>
 424     {
 425         Resolver::from_infcx(fcx.infcx(), &fcx.writeback_errors, reason)
 426     }
 427
 428     fn from_infcx(infcx: &'cx infer::InferCtxt<'cx, 'tcx>,
 429                   writeback_errors: &'cx Cell<bool>,
 430                   reason: ResolveReason)
 431                   -> Resolver<'cx, 'tcx>
 432     {
 433         Resolver { infcx: infcx,
 434                    tcx: infcx.tcx,
 435                    writeback_errors: writeback_errors,
 436                    reason: reason }
 437     }
 438
 439     fn report_error(&self, e: infer::FixupError) {
 440         self.writeback_errors.set(true);
 441         if !self.tcx.sess.has_errors() {
 442             match self.reason {
 443                 ResolvingExpr(span) => {
 444                     span_err!(self.tcx.sess, span, E0101,
 445                         "cannot determine a type for this expression: {}",
 446                         infer::fixup_err_to_string(e));
 447                 }
 448
 449                 ResolvingLocal(span) => {
 450                     span_err!(self.tcx.sess, span, E0102,
 451                         "cannot determine a type for this local variable: {}",
 452                         infer::fixup_err_to_string(e));
 453                 }
 454
 455                 ResolvingPattern(span) => {
 456                     span_err!(self.tcx.sess, span, E0103,
 457                         "cannot determine a type for this pattern binding: {}",
 458                         infer::fixup_err_to_string(e));
 459                 }
 460
 461                 ResolvingUpvar(upvar_id) => {
 462                     let span = self.reason.span(self.tcx);
 463                     span_err!(self.tcx.sess, span, E0104,
 464                         "cannot resolve lifetime for captured variable `{}`: {}",
 465                         self.tcx.local_var_name_str(upvar_id.var_id).to_string(),
 466                         infer::fixup_err_to_string(e));
 467                 }
 468
 469                 ResolvingClosure(_) => {
 470                     let span = self.reason.span(self.tcx);
 471                     span_err!(self.tcx.sess, span, E0196,
 472                               "cannot determine a type for this closure")
 473                 }
 474
 475                 ResolvingFnSig(id) => {
 476                     // any failures here should also fail when
 477                     // resolving the patterns, closure types, or
 478                     // something else.
 479                     let span = self.reason.span(self.tcx);
 480                     self.tcx.sess.delay_span_bug(
 481                         span,
 482                         &format!("cannot resolve some aspect of fn sig for {:?}", id));
 483                 }
 484             }
 485         }
 486     }
 487 }
 488
 489 impl<'cx, 'tcx> TypeFolder<'tcx> for Resolver<'cx, 'tcx> {
 490     fn tcx<'a>(&'a self) -> &'a ty::ctxt<'tcx> {
 491         self.tcx
 492     }
 493
 494     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
 495         match self.infcx.fully_resolve(&t) {
 496             Ok(t) => t,
 497             Err(e) => {
 498                 debug!("Resolver::fold_ty: input type `{:?}` not fully resolvable",
 499                        t);
 500                 self.report_error(e);
 501                 self.tcx().types.err
 502             }
 503         }
 504     }
 505
 506     fn fold_region(&mut self, r: ty::Region) -> ty::Region {
 507         match self.infcx.fully_resolve(&r) {
 508             Ok(r) => r,
 509             Err(e) => {
 510                 self.report_error(e);
 511                 ty::ReStatic
 512             }
 513         }
 514     }
 515 }
 516
 517 ///////////////////////////////////////////////////////////////////////////
 518 // During type check, we store promises with the result of trait
 519 // lookup rather than the actual results (because the results are not
 520 // necessarily available immediately). These routines unwind the
 521 // promises. It is expected that we will have already reported any
 522 // errors that may be encountered, so if the promises store an error,
 523 // a dummy result is returned.