src/librustc/middle/typeck/astconv.rs

   1 // Copyright 2012-2014 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 /*!
  12  * Conversion from AST representation of types to the ty.rs
  13  * representation.  The main routine here is `ast_ty_to_ty()`: each use
  14  * is parameterized by an instance of `AstConv` and a `RegionScope`.
  15  *
  16  * The parameterization of `ast_ty_to_ty()` is because it behaves
  17  * somewhat differently during the collect and check phases,
  18  * particularly with respect to looking up the types of top-level
  19  * items.  In the collect phase, the crate context is used as the
  20  * `AstConv` instance; in this phase, the `get_item_ty()` function
  21  * triggers a recursive call to `ty_of_item()`  (note that
  22  * `ast_ty_to_ty()` will detect recursive types and report an error).
  23  * In the check phase, when the FnCtxt is used as the `AstConv`,
  24  * `get_item_ty()` just looks up the item type in `tcx.tcache`.
  25  *
  26  * The `RegionScope` trait controls what happens when the user does
  27  * not specify a region in some location where a region is required
  28  * (e.g., if the user writes `&Foo` as a type rather than `&'a Foo`).
  29  * See the `rscope` module for more details.
  30  *
  31  * Unlike the `AstConv` trait, the region scope can change as we descend
  32  * the type.  This is to accommodate the fact that (a) fn types are binding
  33  * scopes and (b) the default region may change.  To understand case (a),
  34  * consider something like:
  35  *
  36  *   type foo = { x: &a.int, y: |&a.int| }
  37  *
  38  * The type of `x` is an error because there is no region `a` in scope.
  39  * In the type of `y`, however, region `a` is considered a bound region
  40  * as it does not already appear in scope.
  41  *
  42  * Case (b) says that if you have a type:
  43  *   type foo<'a> = ...;
  44  *   type bar = fn(&foo, &a.foo)
  45  * The fully expanded version of type bar is:
  46  *   type bar = fn(&'foo &, &a.foo<'a>)
  47  * Note that the self region for the `foo` defaulted to `&` in the first
  48  * case but `&a` in the second.  Basically, defaults that appear inside
  49  * an rptr (`&r.T`) use the region `r` that appears in the rptr.
  50  */
  51
  52
  53 use middle::const_eval;
  54 use middle::subst::Subst;
  55 use middle::ty::{substs};
  56 use middle::ty::{ty_param_substs_and_ty};
  57 use middle::ty;
  58 use middle::typeck::rscope;
  59 use middle::typeck::rscope::{RegionScope};
  60 use middle::typeck::lookup_def_tcx;
  61 use util::ppaux::Repr;
  62
  63 use syntax::abi::AbiSet;
  64 use syntax::{ast, ast_util};
  65 use syntax::codemap::Span;
  66 use syntax::owned_slice::OwnedSlice;
  67 use syntax::print::pprust::{lifetime_to_str, path_to_str};
  68
  69 pub trait AstConv {
  70     fn tcx<'a>(&'a self) -> &'a ty::ctxt;
  71     fn get_item_ty(&self, id: ast::DefId) -> ty::ty_param_bounds_and_ty;
  72     fn get_trait_def(&self, id: ast::DefId) -> @ty::TraitDef;
  73
  74     // what type should we use when a type is omitted?
  75     fn ty_infer(&self, span: Span) -> ty::t;
  76 }
  77
  78 pub fn ast_region_to_region(tcx: &ty::ctxt, lifetime: &ast::Lifetime)
  79                             -> ty::Region {
  80     let r = match tcx.named_region_map.find(&lifetime.id) {
  81         None => {
  82             // should have been recorded by the `resolve_lifetime` pass
  83             tcx.sess.span_bug(lifetime.span, "unresolved lifetime");
  84         }
  85
  86         Some(&ast::DefStaticRegion) => {
  87             ty::ReStatic
  88         }
  89
  90         Some(&ast::DefLateBoundRegion(binder_id, _, id)) => {
  91             ty::ReLateBound(binder_id, ty::BrNamed(ast_util::local_def(id),
  92                                                    lifetime.name))
  93         }
  94
  95         Some(&ast::DefEarlyBoundRegion(index, id)) => {
  96             ty::ReEarlyBound(id, index, lifetime.name)
  97         }
  98
  99         Some(&ast::DefFreeRegion(scope_id, id)) => {
 100             ty::ReFree(ty::FreeRegion {
 101                     scope_id: scope_id,
 102                     bound_region: ty::BrNamed(ast_util::local_def(id),
 103                                               lifetime.name)
 104                 })
 105         }
 106     };
 107
 108     debug!("ast_region_to_region(lifetime={} id={}) yields {}",
 109             lifetime_to_str(lifetime),
 110             lifetime.id, r.repr(tcx));
 111
 112     r
 113 }
 114
 115 fn opt_ast_region_to_region<AC:AstConv,RS:RegionScope>(
 116     this: &AC,
 117     rscope: &RS,
 118     default_span: Span,
 119     opt_lifetime: &Option<ast::Lifetime>) -> ty::Region
 120 {
 121     let r = match *opt_lifetime {
 122         Some(ref lifetime) => {
 123             ast_region_to_region(this.tcx(), lifetime)
 124         }
 125
 126         None => {
 127             match rscope.anon_regions(default_span, 1) {
 128                 Err(()) => {
 129                     debug!("optional region in illegal location");
 130                     this.tcx().sess.span_err(
 131                         default_span, "missing lifetime specifier");
 132                     ty::ReStatic
 133                 }
 134
 135                 Ok(rs) => {
 136                     *rs.get(0)
 137                 }
 138             }
 139         }
 140     };
 141
 142     debug!("opt_ast_region_to_region(opt_lifetime={:?}) yields {}",
 143             opt_lifetime.as_ref().map(|e| lifetime_to_str(e)),
 144             r.repr(this.tcx()));
 145
 146     r
 147 }
 148
 149 fn ast_path_substs<AC:AstConv,RS:RegionScope>(
 150     this: &AC,
 151     rscope: &RS,
 152     decl_generics: &ty::Generics,
 153     self_ty: Option<ty::t>,
 154     path: &ast::Path) -> ty::substs
 155 {
 156     /*!
 157      * Given a path `path` that refers to an item `I` with the
 158      * declared generics `decl_generics`, returns an appropriate
 159      * set of substitutions for this particular reference to `I`.
 160      */
 161
 162     let tcx = this.tcx();
 163
 164     // If the type is parameterized by the this region, then replace this
 165     // region with the current anon region binding (in other words,
 166     // whatever & would get replaced with).
 167     let expected_num_region_params = decl_generics.region_param_defs().len();
 168     let supplied_num_region_params = path.segments.last().unwrap().lifetimes.len();
 169     let regions = if expected_num_region_params == supplied_num_region_params {
 170         path.segments.last().unwrap().lifetimes.map(
 171             |l| ast_region_to_region(this.tcx(), l))
 172     } else {
 173         let anon_regions =
 174             rscope.anon_regions(path.span, expected_num_region_params);
 175
 176         if supplied_num_region_params != 0 || anon_regions.is_err() {
 177             tcx.sess.span_err(
 178                 path.span,
 179                 format!("wrong number of lifetime parameters: \
 180                         expected {} but found {}",
 181                         expected_num_region_params,
 182                         supplied_num_region_params));
 183         }
 184
 185         match anon_regions {
 186             Ok(v) => v.move_iter().collect(),
 187             Err(()) => Vec::from_fn(expected_num_region_params,
 188                                     |_| ty::ReStatic) // hokey
 189         }
 190     };
 191
 192     // Convert the type parameters supplied by the user.
 193     let supplied_ty_param_count = path.segments.iter().flat_map(|s| s.types.iter()).len();
 194     let formal_ty_param_count = decl_generics.type_param_defs().len();
 195     let required_ty_param_count = decl_generics.type_param_defs().iter()
 196                                                .take_while(|x| x.default.is_none())
 197                                                .len();
 198     if supplied_ty_param_count < required_ty_param_count {
 199         let expected = if required_ty_param_count < formal_ty_param_count {
 200             "expected at least"
 201         } else {
 202             "expected"
 203         };
 204         this.tcx().sess.span_fatal(path.span,
 205             format!("wrong number of type arguments: {} {} but found {}",
 206                 expected, required_ty_param_count, supplied_ty_param_count));
 207     } else if supplied_ty_param_count > formal_ty_param_count {
 208         let expected = if required_ty_param_count < formal_ty_param_count {
 209             "expected at most"
 210         } else {
 211             "expected"
 212         };
 213         this.tcx().sess.span_fatal(path.span,
 214             format!("wrong number of type arguments: {} {} but found {}",
 215                 expected, formal_ty_param_count, supplied_ty_param_count));
 216     }
 217
 218     if supplied_ty_param_count > required_ty_param_count
 219         && !this.tcx().sess.features.default_type_params.get() {
 220         this.tcx().sess.span_err(path.span, "default type parameters are \
 221                                              experimental and possibly buggy");
 222         this.tcx().sess.span_note(path.span, "add #[feature(default_type_params)] \
 223                                               to the crate attributes to enable");
 224     }
 225
 226     let tps = path.segments.iter().flat_map(|s| s.types.iter())
 227                             .map(|&a_t| ast_ty_to_ty(this, rscope, a_t))
 228                             .collect();
 229
 230     let mut substs = substs {
 231         regions: ty::NonerasedRegions(OwnedSlice::from_vec(regions)),
 232         self_ty: self_ty,
 233         tps: tps
 234     };
 235
 236     for param in decl_generics.type_param_defs()
 237                               .slice_from(supplied_ty_param_count).iter() {
 238         let ty = param.default.unwrap().subst_spanned(tcx, &substs, Some(path.span));
 239         substs.tps.push(ty);
 240     }
 241
 242     substs
 243 }
 244
 245 pub fn ast_path_to_substs_and_ty<AC:AstConv,
 246                                  RS:RegionScope>(
 247                                  this: &AC,
 248                                  rscope: &RS,
 249                                  did: ast::DefId,
 250                                  path: &ast::Path)
 251                                  -> ty_param_substs_and_ty {
 252     let tcx = this.tcx();
 253     let ty::ty_param_bounds_and_ty {
 254         generics: generics,
 255         ty: decl_ty
 256     } = this.get_item_ty(did);
 257
 258     let substs = ast_path_substs(this, rscope, &generics, None, path);
 259     let ty = ty::subst(tcx, &substs, decl_ty);
 260     ty_param_substs_and_ty { substs: substs, ty: ty }
 261 }
 262
 263 pub fn ast_path_to_trait_ref<AC:AstConv,RS:RegionScope>(
 264     this: &AC,
 265     rscope: &RS,
 266     trait_def_id: ast::DefId,
 267     self_ty: Option<ty::t>,
 268     path: &ast::Path) -> @ty::TraitRef
 269 {
 270     let trait_def =
 271         this.get_trait_def(trait_def_id);
 272     let substs =
 273         ast_path_substs(
 274             this,
 275             rscope,
 276             &trait_def.generics,
 277             self_ty,
 278             path);
 279     let trait_ref =
 280         @ty::TraitRef {def_id: trait_def_id,
 281                        substs: substs};
 282     return trait_ref;
 283 }
 284
 285 pub fn ast_path_to_ty<AC:AstConv,RS:RegionScope>(
 286         this: &AC,
 287         rscope: &RS,
 288         did: ast::DefId,
 289         path: &ast::Path)
 290      -> ty_param_substs_and_ty
 291 {
 292     // Look up the polytype of the item and then substitute the provided types
 293     // for any type/region parameters.
 294     let ty::ty_param_substs_and_ty {
 295         substs: substs,
 296         ty: ty
 297     } = ast_path_to_substs_and_ty(this, rscope, did, path);
 298     ty_param_substs_and_ty { substs: substs, ty: ty }
 299 }
 300
 301 pub static NO_REGIONS: uint = 1;
 302 pub static NO_TPS: uint = 2;
 303
 304 fn check_path_args(tcx: &ty::ctxt,
 305                    path: &ast::Path,
 306                    flags: uint) {
 307     if (flags & NO_TPS) != 0u {
 308         if !path.segments.iter().all(|s| s.types.is_empty()) {
 309             tcx.sess.span_err(
 310                 path.span,
 311                 "type parameters are not allowed on this type");
 312         }
 313     }
 314
 315     if (flags & NO_REGIONS) != 0u {
 316         if !path.segments.last().unwrap().lifetimes.is_empty() {
 317             tcx.sess.span_err(
 318                 path.span,
 319                 "region parameters are not allowed on this type");
 320         }
 321     }
 322 }
 323
 324 pub fn ast_ty_to_prim_ty(tcx: &ty::ctxt, ast_ty: &ast::Ty) -> Option<ty::t> {
 325     match ast_ty.node {
 326         ast::TyPath(ref path, _, id) => {
 327             let a_def = match tcx.def_map.borrow().find(&id) {
 328                 None => tcx.sess.span_fatal(
 329                     ast_ty.span, format!("unbound path {}", path_to_str(path))),
 330                 Some(&d) => d
 331             };
 332             match a_def {
 333                 ast::DefPrimTy(nty) => {
 334                     match nty {
 335                         ast::TyBool => {
 336                             check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 337                             Some(ty::mk_bool())
 338                         }
 339                         ast::TyChar => {
 340                             check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 341                             Some(ty::mk_char())
 342                         }
 343                         ast::TyInt(it) => {
 344                             check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 345                             Some(ty::mk_mach_int(it))
 346                         }
 347                         ast::TyUint(uit) => {
 348                             check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 349                             Some(ty::mk_mach_uint(uit))
 350                         }
 351                         ast::TyFloat(ft) => {
 352                             check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 353                             Some(ty::mk_mach_float(ft))
 354                         }
 355                         ast::TyStr => {
 356                             tcx.sess.span_err(ast_ty.span,
 357                                               "bare `str` is not a type");
 358                             // return /something/ so they can at least get more errors
 359                             Some(ty::mk_str(tcx, ty::vstore_uniq))
 360                         }
 361                     }
 362                 }
 363                 _ => None
 364             }
 365         }
 366         _ => None
 367     }
 368 }
 369
 370 // Parses the programmer's textual representation of a type into our
 371 // internal notion of a type.
 372 pub fn ast_ty_to_ty<AC:AstConv, RS:RegionScope>(
 373     this: &AC, rscope: &RS, ast_ty: &ast::Ty) -> ty::t {
 374
 375     fn ast_ty_to_mt<AC:AstConv, RS:RegionScope>(
 376         this: &AC, rscope: &RS, ty: &ast::Ty) -> ty::mt {
 377
 378         ty::mt {ty: ast_ty_to_ty(this, rscope, ty), mutbl: ast::MutImmutable}
 379     }
 380
 381     fn ast_mt_to_mt<AC:AstConv, RS:RegionScope>(
 382         this: &AC, rscope: &RS, mt: &ast::MutTy) -> ty::mt {
 383
 384         ty::mt {ty: ast_ty_to_ty(this, rscope, mt.ty), mutbl: mt.mutbl}
 385     }
 386
 387     enum PointerTy {
 388         Box,
 389         VStore(ty::vstore)
 390     }
 391     impl PointerTy {
 392         fn expect_vstore(&self, tcx: &ty::ctxt, span: Span, ty: &str) -> ty::vstore {
 393             match *self {
 394                 Box => {
 395                     tcx.sess.span_err(span, format!("managed {} are not supported", ty));
 396                     // everything can be ~, so this is a worth substitute
 397                     ty::vstore_uniq
 398                 }
 399                 VStore(vst) => vst
 400             }
 401         }
 402     }
 403
 404     // Handle ~, and & being able to mean strs and vecs.
 405     // If a_seq_ty is a str or a vec, make it a str/vec.
 406     // Also handle first-class trait types.
 407     fn mk_pointer<AC:AstConv,
 408                   RS:RegionScope>(
 409                   this: &AC,
 410                   rscope: &RS,
 411                   a_seq_ty: &ast::MutTy,
 412                   ptr_ty: PointerTy,
 413                   constr: |ty::mt| -> ty::t)
 414                   -> ty::t {
 415         let tcx = this.tcx();
 416         debug!("mk_pointer(ptr_ty={:?})", ptr_ty);
 417
 418         match a_seq_ty.ty.node {
 419             ast::TyVec(ty) => {
 420                 let vst = ptr_ty.expect_vstore(tcx, a_seq_ty.ty.span, "vectors");
 421                 let mut mt = ast_ty_to_mt(this, rscope, ty);
 422                 if a_seq_ty.mutbl == ast::MutMutable {
 423                     mt.mutbl = ast::MutMutable;
 424                 }
 425                 debug!("&[]: vst={:?}", vst);
 426                 return ty::mk_vec(tcx, mt, vst);
 427             }
 428             ast::TyPath(ref path, ref bounds, id) => {
 429                 // Note that the "bounds must be empty if path is not a trait"
 430                 // restriction is enforced in the below case for ty_path, which
 431                 // will run after this as long as the path isn't a trait.
 432                 match tcx.def_map.borrow().find(&id) {
 433                     Some(&ast::DefPrimTy(ast::TyStr)) if
 434                             a_seq_ty.mutbl == ast::MutImmutable => {
 435                         check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 436                         let vst = ptr_ty.expect_vstore(tcx, path.span, "strings");
 437                         return ty::mk_str(tcx, vst);
 438                     }
 439                     Some(&ast::DefTrait(trait_def_id)) => {
 440                         let result = ast_path_to_trait_ref(
 441                             this, rscope, trait_def_id, None, path);
 442                         let trait_store = match ptr_ty {
 443                             VStore(ty::vstore_uniq) => ty::UniqTraitStore,
 444                             VStore(ty::vstore_slice(r)) => {
 445                                 ty::RegionTraitStore(r)
 446                             }
 447                             _ => {
 448                                 tcx.sess.span_err(
 449                                     path.span,
 450                                     "~trait or &trait are the only supported \
 451                                      forms of casting-to-trait");
 452                                 return ty::mk_err();
 453                             }
 454                         };
 455                         let bounds = conv_builtin_bounds(this.tcx(), bounds, trait_store);
 456                         return ty::mk_trait(tcx,
 457                                             result.def_id,
 458                                             result.substs.clone(),
 459                                             trait_store,
 460                                             a_seq_ty.mutbl,
 461                                             bounds);
 462                     }
 463                     _ => {}
 464                 }
 465             }
 466             _ => {}
 467         }
 468
 469         let seq_ty = ast_mt_to_mt(this, rscope, a_seq_ty);
 470         return constr(seq_ty);
 471     }
 472
 473     let tcx = this.tcx();
 474
 475     let mut ast_ty_to_ty_cache = tcx.ast_ty_to_ty_cache.borrow_mut();
 476     match ast_ty_to_ty_cache.find(&ast_ty.id) {
 477         Some(&ty::atttce_resolved(ty)) => return ty,
 478         Some(&ty::atttce_unresolved) => {
 479             tcx.sess.span_fatal(ast_ty.span,
 480                                 "illegal recursive type; insert an enum \
 481                                  or struct in the cycle, if this is \
 482                                  desired");
 483         }
 484         None => { /* go on */ }
 485     }
 486     ast_ty_to_ty_cache.insert(ast_ty.id, ty::atttce_unresolved);
 487     drop(ast_ty_to_ty_cache);
 488
 489     let typ = ast_ty_to_prim_ty(tcx, ast_ty).unwrap_or_else(|| match ast_ty.node {
 490             ast::TyNil => ty::mk_nil(),
 491             ast::TyBot => ty::mk_bot(),
 492             ast::TyBox(ty) => {
 493                 let mt = ast::MutTy { ty: ty, mutbl: ast::MutImmutable };
 494                 mk_pointer(this, rscope, &mt, Box, |tmt| ty::mk_box(tcx, tmt.ty))
 495             }
 496             ast::TyUniq(ty) => {
 497                 let mt = ast::MutTy { ty: ty, mutbl: ast::MutImmutable };
 498                 mk_pointer(this, rscope, &mt, VStore(ty::vstore_uniq),
 499                            |tmt| ty::mk_uniq(tcx, tmt.ty))
 500             }
 501             ast::TyVec(ty) => {
 502                 tcx.sess.span_err(ast_ty.span, "bare `[]` is not a type");
 503                 // return /something/ so they can at least get more errors
 504                 ty::mk_vec(tcx, ast_ty_to_mt(this, rscope, ty), ty::vstore_uniq)
 505             }
 506             ast::TyPtr(ref mt) => {
 507                 ty::mk_ptr(tcx, ast_mt_to_mt(this, rscope, mt))
 508             }
 509             ast::TyRptr(ref region, ref mt) => {
 510                 let r = opt_ast_region_to_region(this, rscope, ast_ty.span, region);
 511                 debug!("ty_rptr r={}", r.repr(this.tcx()));
 512                 mk_pointer(this, rscope, mt, VStore(ty::vstore_slice(r)),
 513                            |tmt| ty::mk_rptr(tcx, r, tmt))
 514             }
 515             ast::TyTup(ref fields) => {
 516                 let flds = fields.iter()
 517                                  .map(|&t| ast_ty_to_ty(this, rscope, t))
 518                                  .collect();
 519                 ty::mk_tup(tcx, flds)
 520             }
 521             ast::TyBareFn(ref bf) => {
 522                 if bf.decl.variadic && !bf.abis.is_c() {
 523                     tcx.sess.span_err(ast_ty.span,
 524                                       "variadic function must have C calling convention");
 525                 }
 526                 ty::mk_bare_fn(tcx, ty_of_bare_fn(this, ast_ty.id, bf.purity,
 527                                                   bf.abis, bf.decl))
 528             }
 529             ast::TyClosure(ref f) => {
 530                 if f.sigil == ast::ManagedSigil {
 531                     tcx.sess.span_err(ast_ty.span,
 532                                       "managed closures are not supported");
 533                 }
 534
 535                 let bounds = conv_builtin_bounds(this.tcx(), &f.bounds, match f.sigil {
 536                         // Use corresponding trait store to figure out default bounds
 537                         // if none were specified.
 538                         ast::BorrowedSigil => ty::RegionTraitStore(ty::ReEmpty), // dummy region
 539                         ast::OwnedSigil    => ty::UniqTraitStore,
 540                         ast::ManagedSigil  => return ty::mk_err()
 541                     });
 542                 let fn_decl = ty_of_closure(this,
 543                                             rscope,
 544                                             ast_ty.id,
 545                                             f.sigil,
 546                                             f.purity,
 547                                             f.onceness,
 548                                             bounds,
 549                                             &f.region,
 550                                             f.decl,
 551                                             None,
 552                                             ast_ty.span);
 553                 ty::mk_closure(tcx, fn_decl)
 554             }
 555             ast::TyPath(ref path, ref bounds, id) => {
 556                 let a_def = match tcx.def_map.borrow().find(&id) {
 557                     None => tcx.sess.span_fatal(
 558                         ast_ty.span, format!("unbound path {}", path_to_str(path))),
 559                     Some(&d) => d
 560                 };
 561                 // Kind bounds on path types are only supported for traits.
 562                 match a_def {
 563                     // But don't emit the error if the user meant to do a trait anyway.
 564                     ast::DefTrait(..) => { },
 565                     _ if bounds.is_some() =>
 566                         tcx.sess.span_err(ast_ty.span,
 567                                           "kind bounds can only be used on trait types"),
 568                     _ => { },
 569                 }
 570                 match a_def {
 571                     ast::DefTrait(_) => {
 572                         let path_str = path_to_str(path);
 573                         tcx.sess.span_err(
 574                             ast_ty.span,
 575                             format!("reference to trait `{}` where a type is expected; \
 576                                     try `@{}`, `~{}`, or `&{}`",
 577                                     path_str, path_str, path_str, path_str));
 578                         ty::mk_err()
 579                     }
 580                     ast::DefTy(did) | ast::DefStruct(did) => {
 581                         ast_path_to_ty(this, rscope, did, path).ty
 582                     }
 583                     ast::DefTyParam(id, n) => {
 584                         check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 585                         ty::mk_param(tcx, n, id)
 586                     }
 587                     ast::DefSelfTy(id) => {
 588                         // n.b.: resolve guarantees that the this type only appears in a
 589                         // trait, which we rely upon in various places when creating
 590                         // substs
 591                         check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 592                         let did = ast_util::local_def(id);
 593                         ty::mk_self(tcx, did)
 594                     }
 595                     ast::DefMod(id) => {
 596                         tcx.sess.span_fatal(ast_ty.span,
 597                             format!("found module name used as a type: {}",
 598                                     tcx.map.node_to_str(id.node)));
 599                     }
 600                     ast::DefPrimTy(_) => {
 601                         fail!("DefPrimTy arm missed in previous ast_ty_to_prim_ty call");
 602                     }
 603                     _ => {
 604                         tcx.sess.span_fatal(ast_ty.span,
 605                             format!("found value name used as a type: {:?}", a_def));
 606                     }
 607                 }
 608             }
 609             ast::TyFixedLengthVec(ty, e) => {
 610                 match const_eval::eval_const_expr_partial(tcx, e) {
 611                     Ok(ref r) => {
 612                         match *r {
 613                             const_eval::const_int(i) =>
 614                                 ty::mk_vec(tcx, ast_ty_to_mt(this, rscope, ty),
 615                                            ty::vstore_fixed(i as uint)),
 616                             const_eval::const_uint(i) =>
 617                                 ty::mk_vec(tcx, ast_ty_to_mt(this, rscope, ty),
 618                                            ty::vstore_fixed(i as uint)),
 619                             _ => {
 620                                 tcx.sess.span_fatal(
 621                                     ast_ty.span, "expected constant expr for vector length");
 622                             }
 623                         }
 624                     }
 625                     Err(ref r) => {
 626                         tcx.sess.span_fatal(
 627                             ast_ty.span,
 628                             format!("expected constant expr for vector length: {}", *r));
 629                     }
 630                 }
 631             }
 632             ast::TyTypeof(_e) => {
 633                 tcx.sess.span_bug(ast_ty.span, "typeof is reserved but unimplemented");
 634             }
 635             ast::TyInfer => {
 636                 // TyInfer also appears as the type of arguments or return
 637                 // values in a ExprFnBlock or ExprProc, or as the type of
 638                 // local variables. Both of these cases are handled specially
 639                 // and will not descend into this routine.
 640                 this.ty_infer(ast_ty.span)
 641             }
 642         });
 643
 644     tcx.ast_ty_to_ty_cache.borrow_mut().insert(ast_ty.id, ty::atttce_resolved(typ));
 645     return typ;
 646 }
 647
 648 pub fn ty_of_arg<AC: AstConv, RS: RegionScope>(this: &AC, rscope: &RS, a: &ast::Arg,
 649                                                expected_ty: Option<ty::t>) -> ty::t {
 650     match a.ty.node {
 651         ast::TyInfer if expected_ty.is_some() => expected_ty.unwrap(),
 652         ast::TyInfer => this.ty_infer(a.ty.span),
 653         _ => ast_ty_to_ty(this, rscope, a.ty),
 654     }
 655 }
 656
 657 struct SelfInfo {
 658     untransformed_self_ty: ty::t,
 659     explicit_self: ast::ExplicitSelf
 660 }
 661
 662 pub fn ty_of_method<AC:AstConv>(
 663     this: &AC,
 664     id: ast::NodeId,
 665     purity: ast::Purity,
 666     untransformed_self_ty: ty::t,
 667     explicit_self: ast::ExplicitSelf,
 668     decl: &ast::FnDecl) -> ty::BareFnTy {
 669     ty_of_method_or_bare_fn(this, id, purity, AbiSet::Rust(), Some(SelfInfo {
 670         untransformed_self_ty: untransformed_self_ty,
 671         explicit_self: explicit_self
 672     }), decl)
 673 }
 674
 675 pub fn ty_of_bare_fn<AC:AstConv>(this: &AC, id: ast::NodeId,
 676                                  purity: ast::Purity, abi: AbiSet,
 677                                  decl: &ast::FnDecl) -> ty::BareFnTy {
 678     ty_of_method_or_bare_fn(this, id, purity, abi, None, decl)
 679 }
 680
 681 fn ty_of_method_or_bare_fn<AC:AstConv>(this: &AC, id: ast::NodeId,
 682                                        purity: ast::Purity, abi: AbiSet,
 683                                        opt_self_info: Option<SelfInfo>,
 684                                        decl: &ast::FnDecl) -> ty::BareFnTy {
 685     debug!("ty_of_method_or_bare_fn");
 686
 687     // new region names that appear inside of the fn decl are bound to
 688     // that function type
 689     let rb = rscope::BindingRscope::new(id);
 690
 691     let self_ty = opt_self_info.and_then(|self_info| {
 692         match self_info.explicit_self.node {
 693             ast::SelfStatic => None,
 694             ast::SelfValue => {
 695                 Some(self_info.untransformed_self_ty)
 696             }
 697             ast::SelfRegion(ref lifetime, mutability) => {
 698                 let region =
 699                     opt_ast_region_to_region(this, &rb,
 700                                              self_info.explicit_self.span,
 701                                              lifetime);
 702                 Some(ty::mk_rptr(this.tcx(), region,
 703                                  ty::mt {ty: self_info.untransformed_self_ty,
 704                                          mutbl: mutability}))
 705             }
 706             ast::SelfUniq => {
 707                 Some(ty::mk_uniq(this.tcx(), self_info.untransformed_self_ty))
 708             }
 709         }
 710     });
 711
 712     // HACK(eddyb) replace the fake self type in the AST with the actual type.
 713     let input_tys = if self_ty.is_some() {
 714         decl.inputs.slice_from(1)
 715     } else {
 716         decl.inputs.as_slice()
 717     };
 718     let input_tys = input_tys.iter().map(|a| ty_of_arg(this, &rb, a, None));
 719
 720     let self_and_input_tys = self_ty.move_iter().chain(input_tys).collect();
 721
 722     let output_ty = match decl.output.node {
 723         ast::TyInfer => this.ty_infer(decl.output.span),
 724         _ => ast_ty_to_ty(this, &rb, decl.output)
 725     };
 726
 727     return ty::BareFnTy {
 728         purity: purity,
 729         abis: abi,
 730         sig: ty::FnSig {
 731             binder_id: id,
 732             inputs: self_and_input_tys,
 733             output: output_ty,
 734             variadic: decl.variadic
 735         }
 736     };
 737 }
 738
 739 pub fn ty_of_closure<AC:AstConv,RS:RegionScope>(
 740     this: &AC,
 741     rscope: &RS,
 742     id: ast::NodeId,
 743     sigil: ast::Sigil,
 744     purity: ast::Purity,
 745     onceness: ast::Onceness,
 746     bounds: ty::BuiltinBounds,
 747     opt_lifetime: &Option<ast::Lifetime>,
 748     decl: &ast::FnDecl,
 749     expected_sig: Option<ty::FnSig>,
 750     span: Span)
 751     -> ty::ClosureTy
 752 {
 753     debug!("ty_of_fn_decl");
 754
 755     // resolve the function bound region in the original region
 756     // scope `rscope`, not the scope of the function parameters
 757     let bound_region = match opt_lifetime {
 758         &Some(ref lifetime) => {
 759             ast_region_to_region(this.tcx(), lifetime)
 760         }
 761         &None => {
 762             match sigil {
 763                 ast::OwnedSigil | ast::ManagedSigil => {
 764                     // @fn(), ~fn() default to static as the bound
 765                     // on their upvars:
 766                     ty::ReStatic
 767                 }
 768                 ast::BorrowedSigil => {
 769                     // || defaults as normal for an omitted lifetime:
 770                     opt_ast_region_to_region(this, rscope, span, opt_lifetime)
 771                 }
 772             }
 773         }
 774     };
 775
 776     // new region names that appear inside of the fn decl are bound to
 777     // that function type
 778     let rb = rscope::BindingRscope::new(id);
 779
 780     let input_tys = decl.inputs.iter().enumerate().map(|(i, a)| {
 781         let expected_arg_ty = expected_sig.as_ref().and_then(|e| {
 782             // no guarantee that the correct number of expected args
 783             // were supplied
 784             if i < e.inputs.len() {
 785                 Some(*e.inputs.get(i))
 786             } else {
 787                 None
 788             }
 789         });
 790         ty_of_arg(this, &rb, a, expected_arg_ty)
 791     }).collect();
 792
 793     let expected_ret_ty = expected_sig.map(|e| e.output);
 794     let output_ty = match decl.output.node {
 795         ast::TyInfer if expected_ret_ty.is_some() => expected_ret_ty.unwrap(),
 796         ast::TyInfer => this.ty_infer(decl.output.span),
 797         _ => ast_ty_to_ty(this, &rb, decl.output)
 798     };
 799
 800     ty::ClosureTy {
 801         purity: purity,
 802         sigil: sigil,
 803         onceness: onceness,
 804         region: bound_region,
 805         bounds: bounds,
 806         sig: ty::FnSig {binder_id: id,
 807                         inputs: input_tys,
 808                         output: output_ty,
 809                         variadic: decl.variadic}
 810     }
 811 }
 812
 813 fn conv_builtin_bounds(tcx: &ty::ctxt, ast_bounds: &Option<OwnedSlice<ast::TyParamBound>>,
 814                        store: ty::TraitStore)
 815                        -> ty::BuiltinBounds {
 816     //! Converts a list of bounds from the AST into a `BuiltinBounds`
 817     //! struct. Reports an error if any of the bounds that appear
 818     //! in the AST refer to general traits and not the built-in traits
 819     //! like `Send`. Used to translate the bounds that
 820     //! appear in closure and trait types, where only builtin bounds are
 821     //! legal.
 822     //! If no bounds were specified, we choose a "default" bound based on
 823     //! the allocation type of the fn/trait, as per issue #7264. The user can
 824     //! override this with an empty bounds list, e.g. "~fn:()" or "~Trait:".
 825
 826     match (ast_bounds, store) {
 827         (&Some(ref bound_vec), _) => {
 828             let mut builtin_bounds = ty::EmptyBuiltinBounds();
 829             for ast_bound in bound_vec.iter() {
 830                 match *ast_bound {
 831                     ast::TraitTyParamBound(ref b) => {
 832                         match lookup_def_tcx(tcx, b.path.span, b.ref_id) {
 833                             ast::DefTrait(trait_did) => {
 834                                 if ty::try_add_builtin_trait(tcx, trait_did,
 835                                                              &mut builtin_bounds) {
 836                                     continue; // success
 837                                 }
 838                             }
 839                             _ => { }
 840                         }
 841                         tcx.sess.span_fatal(
 842                             b.path.span,
 843                             format!("only the builtin traits can be used \
 844                                   as closure or object bounds"));
 845                     }
 846                     ast::RegionTyParamBound => {
 847                         builtin_bounds.add(ty::BoundStatic);
 848                     }
 849                 }
 850             }
 851             builtin_bounds
 852         },
 853         // ~Trait is sugar for ~Trait:Send.
 854         (&None, ty::UniqTraitStore) => {
 855             let mut set = ty::EmptyBuiltinBounds(); set.add(ty::BoundSend); set
 856         }
 857         // &'static Trait is sugar for &'static Trait:'static.
 858         (&None, ty::RegionTraitStore(ty::ReStatic)) => {
 859             let mut set = ty::EmptyBuiltinBounds(); set.add(ty::BoundStatic); set
 860         }
 861         // &'r Trait is sugar for &'r Trait:<no-bounds>.
 862         (&None, ty::RegionTraitStore(..)) => ty::EmptyBuiltinBounds(),
 863     }
 864 }