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::pat_util;
  19 use middle::ty::{self, Ty, MethodCall, MethodCallee};
  20 use middle::ty_fold::{TypeFolder,TypeFoldable};
  21 use middle::infer;
  22 use write_substs_to_tcx;
  23 use write_ty_to_tcx;
  24 use util::ppaux::Repr;
  25
  26 use std::cell::Cell;
  27
  28 use syntax::ast;
  29 use syntax::codemap::{DUMMY_SP, Span};
  30 use syntax::print::pprust::pat_to_string;
  31 use syntax::visit;
  32 use syntax::visit::Visitor;
  33
  34 ///////////////////////////////////////////////////////////////////////////
  35 // Entry point functions
  36
  37 pub fn resolve_type_vars_in_expr(fcx: &FnCtxt, e: &ast::Expr) {
  38     assert_eq!(fcx.writeback_errors.get(), false);
  39     let mut wbcx = WritebackCx::new(fcx);
  40     wbcx.visit_expr(e);
  41     wbcx.visit_upvar_borrow_map();
  42     wbcx.visit_unboxed_closures();
  43     wbcx.visit_object_cast_map();
  44 }
  45
  46 pub fn resolve_type_vars_in_fn(fcx: &FnCtxt,
  47                                decl: &ast::FnDecl,
  48                                blk: &ast::Block) {
  49     assert_eq!(fcx.writeback_errors.get(), false);
  50     let mut wbcx = WritebackCx::new(fcx);
  51     wbcx.visit_block(blk);
  52     for arg in decl.inputs.iter() {
  53         wbcx.visit_node_id(ResolvingPattern(arg.pat.span), arg.id);
  54         wbcx.visit_pat(&*arg.pat);
  55
  56         // Privacy needs the type for the whole pattern, not just each binding
  57         if !pat_util::pat_is_binding(&fcx.tcx().def_map, &*arg.pat) {
  58             wbcx.visit_node_id(ResolvingPattern(arg.pat.span),
  59                                arg.pat.id);
  60         }
  61     }
  62     wbcx.visit_upvar_borrow_map();
  63     wbcx.visit_unboxed_closures();
  64     wbcx.visit_object_cast_map();
  65 }
  66
  67 ///////////////////////////////////////////////////////////////////////////
  68 // The Writerback context. This visitor walks the AST, checking the
  69 // fn-specific tables to find references to types or regions. It
  70 // resolves those regions to remove inference variables and writes the
  71 // final result back into the master tables in the tcx. Here and
  72 // there, it applies a few ad-hoc checks that were not convenient to
  73 // do elsewhere.
  74
  75 struct WritebackCx<'cx, 'tcx: 'cx> {
  76     fcx: &'cx FnCtxt<'cx, 'tcx>,
  77 }
  78
  79 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
  80     fn new(fcx: &'cx FnCtxt<'cx, 'tcx>) -> WritebackCx<'cx, 'tcx> {
  81         WritebackCx { fcx: fcx }
  82     }
  83
  84     fn tcx(&self) -> &'cx ty::ctxt<'tcx> {
  85         self.fcx.tcx()
  86     }
  87 }
  88
  89 ///////////////////////////////////////////////////////////////////////////
  90 // Impl of Visitor for Resolver
  91 //
  92 // This is the master code which walks the AST. It delegates most of
  93 // the heavy lifting to the generic visit and resolve functions
  94 // below. In general, a function is made into a `visitor` if it must
  95 // traffic in node-ids or update tables in the type context etc.
  96
  97 impl<'cx, 'tcx, 'v> Visitor<'v> for WritebackCx<'cx, 'tcx> {
  98     fn visit_item(&mut self, _: &ast::Item) {
  99         // Ignore items
 100     }
 101
 102     fn visit_stmt(&mut self, s: &ast::Stmt) {
 103         if self.fcx.writeback_errors.get() {
 104             return;
 105         }
 106
 107         self.visit_node_id(ResolvingExpr(s.span), ty::stmt_node_id(s));
 108         visit::walk_stmt(self, s);
 109     }
 110
 111     fn visit_expr(&mut self, e: &ast::Expr) {
 112         if self.fcx.writeback_errors.get() {
 113             return;
 114         }
 115
 116         self.visit_node_id(ResolvingExpr(e.span), e.id);
 117         self.visit_method_map_entry(ResolvingExpr(e.span),
 118                                     MethodCall::expr(e.id));
 119
 120         match e.node {
 121             ast::ExprClosure(_, _, ref decl, _) => {
 122                 for input in decl.inputs.iter() {
 123                     let _ = self.visit_node_id(ResolvingExpr(e.span),
 124                                                input.id);
 125                 }
 126             }
 127             _ => {}
 128         }
 129
 130         visit::walk_expr(self, e);
 131     }
 132
 133     fn visit_block(&mut self, b: &ast::Block) {
 134         if self.fcx.writeback_errors.get() {
 135             return;
 136         }
 137
 138         self.visit_node_id(ResolvingExpr(b.span), b.id);
 139         visit::walk_block(self, b);
 140     }
 141
 142     fn visit_pat(&mut self, p: &ast::Pat) {
 143         if self.fcx.writeback_errors.get() {
 144             return;
 145         }
 146
 147         self.visit_node_id(ResolvingPattern(p.span), p.id);
 148
 149         debug!("Type for pattern binding {} (id {}) resolved to {}",
 150                pat_to_string(p),
 151                p.id,
 152                ty::node_id_to_type(self.tcx(), p.id).repr(self.tcx()));
 153
 154         visit::walk_pat(self, p);
 155     }
 156
 157     fn visit_local(&mut self, l: &ast::Local) {
 158         if self.fcx.writeback_errors.get() {
 159             return;
 160         }
 161
 162         let var_ty = self.fcx.local_ty(l.span, l.id);
 163         let var_ty = self.resolve(&var_ty, ResolvingLocal(l.span));
 164         write_ty_to_tcx(self.tcx(), l.id, var_ty);
 165         visit::walk_local(self, l);
 166     }
 167
 168     fn visit_ty(&mut self, t: &ast::Ty) {
 169         match t.node {
 170             ast::TyFixedLengthVec(ref ty, ref count_expr) => {
 171                 self.visit_ty(&**ty);
 172                 write_ty_to_tcx(self.tcx(), count_expr.id, self.tcx().types.uint);
 173             }
 174             _ => visit::walk_ty(self, t)
 175         }
 176     }
 177 }
 178
 179 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 180     fn visit_upvar_borrow_map(&self) {
 181         if self.fcx.writeback_errors.get() {
 182             return;
 183         }
 184
 185         for (upvar_id, upvar_borrow) in self.fcx.inh.upvar_borrow_map.borrow().iter() {
 186             let r = upvar_borrow.region;
 187             let r = self.resolve(&r, ResolvingUpvar(*upvar_id));
 188             let new_upvar_borrow = ty::UpvarBorrow { kind: upvar_borrow.kind,
 189                                                      region: r };
 190             debug!("Upvar borrow for {} resolved to {}",
 191                    upvar_id.repr(self.tcx()),
 192                    new_upvar_borrow.repr(self.tcx()));
 193             self.fcx.tcx().upvar_borrow_map.borrow_mut().insert(
 194                 *upvar_id, new_upvar_borrow);
 195         }
 196     }
 197
 198     fn visit_unboxed_closures(&self) {
 199         if self.fcx.writeback_errors.get() {
 200             return
 201         }
 202
 203         for (def_id, unboxed_closure) in self.fcx
 204                                              .inh
 205                                              .unboxed_closures
 206                                              .borrow()
 207                                              .iter() {
 208             let closure_ty = self.resolve(&unboxed_closure.closure_type,
 209                                           ResolvingUnboxedClosure(*def_id));
 210             let unboxed_closure = ty::UnboxedClosure {
 211                 closure_type: closure_ty,
 212                 kind: unboxed_closure.kind,
 213             };
 214             self.fcx
 215                 .tcx()
 216                 .unboxed_closures
 217                 .borrow_mut()
 218                 .insert(*def_id, unboxed_closure);
 219         }
 220     }
 221
 222     fn visit_object_cast_map(&self) {
 223         if self.fcx.writeback_errors.get() {
 224             return
 225         }
 226
 227         for (&node_id, trait_ref) in self.fcx
 228                                             .inh
 229                                             .object_cast_map
 230                                             .borrow()
 231                                             .iter()
 232         {
 233             let span = ty::expr_span(self.tcx(), node_id);
 234             let reason = ResolvingExpr(span);
 235             let closure_ty = self.resolve(trait_ref, reason);
 236             self.tcx()
 237                 .object_cast_map
 238                 .borrow_mut()
 239                 .insert(node_id, closure_ty);
 240         }
 241     }
 242
 243     fn visit_node_id(&self, reason: ResolveReason, id: ast::NodeId) {
 244         // Resolve any borrowings for the node with id `id`
 245         self.visit_adjustments(reason, id);
 246
 247         // Resolve the type of the node with id `id`
 248         let n_ty = self.fcx.node_ty(id);
 249         let n_ty = self.resolve(&n_ty, reason);
 250         write_ty_to_tcx(self.tcx(), id, n_ty);
 251         debug!("Node {} has type {}", id, n_ty.repr(self.tcx()));
 252
 253         // Resolve any substitutions
 254         self.fcx.opt_node_ty_substs(id, |item_substs| {
 255             write_substs_to_tcx(self.tcx(), id,
 256                                 self.resolve(item_substs, reason));
 257         });
 258     }
 259
 260     fn visit_adjustments(&self, reason: ResolveReason, id: ast::NodeId) {
 261         match self.fcx.inh.adjustments.borrow_mut().remove(&id) {
 262             None => {
 263                 debug!("No adjustments for node {}", id);
 264             }
 265
 266             Some(adjustment) => {
 267                 let adj_object = ty::adjust_is_object(&adjustment);
 268                 let resolved_adjustment = match adjustment {
 269                     ty::AdjustReifyFnPointer(def_id) => {
 270                         ty::AdjustReifyFnPointer(def_id)
 271                     }
 272
 273                     ty::AdjustDerefRef(adj) => {
 274                         for autoderef in range(0, adj.autoderefs) {
 275                             let method_call = MethodCall::autoderef(id, autoderef);
 276                             self.visit_method_map_entry(reason, method_call);
 277                         }
 278
 279                         if adj_object {
 280                             let method_call = MethodCall::autoobject(id);
 281                             self.visit_method_map_entry(reason, method_call);
 282                         }
 283
 284                         ty::AdjustDerefRef(ty::AutoDerefRef {
 285                             autoderefs: adj.autoderefs,
 286                             autoref: self.resolve(&adj.autoref, reason),
 287                         })
 288                     }
 289                 };
 290                 debug!("Adjustments for node {}: {:?}", id, resolved_adjustment);
 291                 self.tcx().adjustments.borrow_mut().insert(
 292                     id, resolved_adjustment);
 293             }
 294         }
 295     }
 296
 297     fn visit_method_map_entry(&self,
 298                               reason: ResolveReason,
 299                               method_call: MethodCall) {
 300         // Resolve any method map entry
 301         match self.fcx.inh.method_map.borrow_mut().remove(&method_call) {
 302             Some(method) => {
 303                 debug!("writeback::resolve_method_map_entry(call={:?}, entry={})",
 304                        method_call,
 305                        method.repr(self.tcx()));
 306                 let new_method = MethodCallee {
 307                     origin: self.resolve(&method.origin, reason),
 308                     ty: self.resolve(&method.ty, reason),
 309                     substs: self.resolve(&method.substs, reason),
 310                 };
 311
 312                 self.tcx().method_map.borrow_mut().insert(
 313                     method_call,
 314                     new_method);
 315             }
 316             None => {}
 317         }
 318     }
 319
 320     fn resolve<T:TypeFoldable<'tcx>>(&self, t: &T, reason: ResolveReason) -> T {
 321         t.fold_with(&mut Resolver::new(self.fcx, reason))
 322     }
 323 }
 324
 325 ///////////////////////////////////////////////////////////////////////////
 326 // Resolution reason.
 327
 328 #[derive(Copy)]
 329 enum ResolveReason {
 330     ResolvingExpr(Span),
 331     ResolvingLocal(Span),
 332     ResolvingPattern(Span),
 333     ResolvingUpvar(ty::UpvarId),
 334     ResolvingUnboxedClosure(ast::DefId),
 335 }
 336
 337 impl ResolveReason {
 338     fn span(&self, tcx: &ty::ctxt) -> Span {
 339         match *self {
 340             ResolvingExpr(s) => s,
 341             ResolvingLocal(s) => s,
 342             ResolvingPattern(s) => s,
 343             ResolvingUpvar(upvar_id) => {
 344                 ty::expr_span(tcx, upvar_id.closure_expr_id)
 345             }
 346             ResolvingUnboxedClosure(did) => {
 347                 if did.krate == ast::LOCAL_CRATE {
 348                     ty::expr_span(tcx, did.node)
 349                 } else {
 350                     DUMMY_SP
 351                 }
 352             }
 353         }
 354     }
 355 }
 356
 357 ///////////////////////////////////////////////////////////////////////////
 358 // The Resolver. This is the type folding engine that detects
 359 // unresolved types and so forth.
 360
 361 struct Resolver<'cx, 'tcx: 'cx> {
 362     tcx: &'cx ty::ctxt<'tcx>,
 363     infcx: &'cx infer::InferCtxt<'cx, 'tcx>,
 364     writeback_errors: &'cx Cell<bool>,
 365     reason: ResolveReason,
 366 }
 367
 368 impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
 369     fn new(fcx: &'cx FnCtxt<'cx, 'tcx>,
 370            reason: ResolveReason)
 371            -> Resolver<'cx, 'tcx>
 372     {
 373         Resolver::from_infcx(fcx.infcx(), &fcx.writeback_errors, reason)
 374     }
 375
 376     fn from_infcx(infcx: &'cx infer::InferCtxt<'cx, 'tcx>,
 377                   writeback_errors: &'cx Cell<bool>,
 378                   reason: ResolveReason)
 379                   -> Resolver<'cx, 'tcx>
 380     {
 381         Resolver { infcx: infcx,
 382                    tcx: infcx.tcx,
 383                    writeback_errors: writeback_errors,
 384                    reason: reason }
 385     }
 386
 387     fn report_error(&self, e: infer::fixup_err) {
 388         self.writeback_errors.set(true);
 389         if !self.tcx.sess.has_errors() {
 390             match self.reason {
 391                 ResolvingExpr(span) => {
 392                     span_err!(self.tcx.sess, span, E0101,
 393                         "cannot determine a type for this expression: {}",
 394                         infer::fixup_err_to_string(e));
 395                 }
 396
 397                 ResolvingLocal(span) => {
 398                     span_err!(self.tcx.sess, span, E0102,
 399                         "cannot determine a type for this local variable: {}",
 400                         infer::fixup_err_to_string(e));
 401                 }
 402
 403                 ResolvingPattern(span) => {
 404                     span_err!(self.tcx.sess, span, E0103,
 405                         "cannot determine a type for this pattern binding: {}",
 406                         infer::fixup_err_to_string(e));
 407                 }
 408
 409                 ResolvingUpvar(upvar_id) => {
 410                     let span = self.reason.span(self.tcx);
 411                     span_err!(self.tcx.sess, span, E0104,
 412                         "cannot resolve lifetime for captured variable `{}`: {}",
 413                         ty::local_var_name_str(self.tcx, upvar_id.var_id).get().to_string(),
 414                         infer::fixup_err_to_string(e));
 415                 }
 416
 417                 ResolvingUnboxedClosure(_) => {
 418                     let span = self.reason.span(self.tcx);
 419                     self.tcx.sess.span_err(span,
 420                                            "cannot determine a type for this \
 421                                             unboxed closure")
 422                 }
 423             }
 424         }
 425     }
 426 }
 427
 428 impl<'cx, 'tcx> TypeFolder<'tcx> for Resolver<'cx, 'tcx> {
 429     fn tcx<'a>(&'a self) -> &'a ty::ctxt<'tcx> {
 430         self.tcx
 431     }
 432
 433     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
 434         match self.infcx.fully_resolve(&t) {
 435             Ok(t) => t,
 436             Err(e) => {
 437                 debug!("Resolver::fold_ty: input type `{}` not fully resolvable",
 438                        t.repr(self.tcx));
 439                 self.report_error(e);
 440                 self.tcx().types.err
 441             }
 442         }
 443     }
 444
 445     fn fold_region(&mut self, r: ty::Region) -> ty::Region {
 446         match self.infcx.fully_resolve(&r) {
 447             Ok(r) => r,
 448             Err(e) => {
 449                 self.report_error(e);
 450                 ty::ReStatic
 451             }
 452         }
 453     }
 454 }
 455
 456 ///////////////////////////////////////////////////////////////////////////
 457 // During type check, we store promises with the result of trait
 458 // lookup rather than the actual results (because the results are not
 459 // necessarily available immediately). These routines unwind the
 460 // promises. It is expected that we will have already reported any
 461 // errors that may be encountered, so if the promises store an error,
 462 // a dummy result is returned.