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 use middle::const_eval;
  52 use middle::def;
  53 use middle::resolve_lifetime as rl;
  54 use middle::subst::{FnSpace, TypeSpace, AssocSpace, SelfSpace, Subst, Substs};
  55 use middle::subst::{VecPerParamSpace};
  56 use middle::ty::{mod, Ty};
  57 use middle::typeck::lookup_def_tcx;
  58 use middle::typeck::rscope::{UnelidableRscope, RegionScope, SpecificRscope,
  59                              ShiftedRscope, BindingRscope};
  60 use middle::typeck::rscope;
  61 use middle::typeck::TypeAndSubsts;
  62 use util::nodemap::DefIdMap;
  63 use util::ppaux::{Repr, UserString};
  64
  65 use std::rc::Rc;
  66 use std::iter::AdditiveIterator;
  67 use syntax::{abi, ast, ast_util};
  68 use syntax::codemap::Span;
  69 use syntax::parse::token;
  70 use syntax::print::pprust;
  71
  72 pub trait AstConv<'tcx> {
  73     fn tcx<'a>(&'a self) -> &'a ty::ctxt<'tcx>;
  74     fn get_item_ty(&self, id: ast::DefId) -> ty::Polytype<'tcx>;
  75     fn get_trait_def(&self, id: ast::DefId) -> Rc<ty::TraitDef<'tcx>>;
  76
  77     /// What type should we use when a type is omitted?
  78     fn ty_infer(&self, span: Span) -> Ty<'tcx>;
  79
  80     /// Returns true if associated types from the given trait and type are
  81     /// allowed to be used here and false otherwise.
  82     fn associated_types_of_trait_are_valid(&self,
  83                                            ty: Ty<'tcx>,
  84                                            trait_id: ast::DefId)
  85                                            -> bool;
  86
  87     /// Returns the binding of the given associated type for some type.
  88     fn associated_type_binding(&self,
  89                                span: Span,
  90                                ty: Option<Ty<'tcx>>,
  91                                trait_id: ast::DefId,
  92                                associated_type_id: ast::DefId)
  93                                -> Ty<'tcx>;
  94 }
  95
  96 pub fn ast_region_to_region(tcx: &ty::ctxt, lifetime: &ast::Lifetime)
  97                             -> ty::Region {
  98     let r = match tcx.named_region_map.get(&lifetime.id) {
  99         None => {
 100             // should have been recorded by the `resolve_lifetime` pass
 101             tcx.sess.span_bug(lifetime.span, "unresolved lifetime");
 102         }
 103
 104         Some(&rl::DefStaticRegion) => {
 105             ty::ReStatic
 106         }
 107
 108         Some(&rl::DefLateBoundRegion(debruijn, id)) => {
 109             ty::ReLateBound(debruijn, ty::BrNamed(ast_util::local_def(id), lifetime.name))
 110         }
 111
 112         Some(&rl::DefEarlyBoundRegion(space, index, id)) => {
 113             ty::ReEarlyBound(id, space, index, lifetime.name)
 114         }
 115
 116         Some(&rl::DefFreeRegion(scope, id)) => {
 117             ty::ReFree(ty::FreeRegion {
 118                     scope: scope,
 119                     bound_region: ty::BrNamed(ast_util::local_def(id),
 120                                               lifetime.name)
 121                 })
 122         }
 123     };
 124
 125     debug!("ast_region_to_region(lifetime={} id={}) yields {}",
 126            lifetime.repr(tcx),
 127            lifetime.id,
 128            r.repr(tcx));
 129
 130     r
 131 }
 132
 133 pub fn opt_ast_region_to_region<'tcx, AC: AstConv<'tcx>, RS: RegionScope>(
 134     this: &AC,
 135     rscope: &RS,
 136     default_span: Span,
 137     opt_lifetime: &Option<ast::Lifetime>) -> ty::Region
 138 {
 139     let r = match *opt_lifetime {
 140         Some(ref lifetime) => {
 141             ast_region_to_region(this.tcx(), lifetime)
 142         }
 143
 144         None => {
 145             match rscope.anon_regions(default_span, 1) {
 146                 Err(v) => {
 147                     debug!("optional region in illegal location");
 148                     span_err!(this.tcx().sess, default_span, E0106,
 149                         "missing lifetime specifier");
 150                     match v {
 151                         Some(v) => {
 152                             let mut m = String::new();
 153                             let len = v.len();
 154                             for (i, (name, n)) in v.into_iter().enumerate() {
 155                                 m.push_str(if n == 1 {
 156                                     format!("`{}`", name)
 157                                 } else {
 158                                     format!("one of `{}`'s {} elided lifetimes", name, n)
 159                                 }.as_slice());
 160
 161                                 if len == 2 && i == 0 {
 162                                     m.push_str(" or ");
 163                                 } else if i == len - 2 {
 164                                     m.push_str(", or ");
 165                                 } else if i != len - 1 {
 166                                     m.push_str(", ");
 167                                 }
 168                             }
 169                             if len == 1 {
 170                                 span_help!(this.tcx().sess, default_span,
 171                                     "this function's return type contains a borrowed value, but \
 172                                      the signature does not say which {} it is borrowed from",
 173                                     m);
 174                             } else if len == 0 {
 175                                 span_help!(this.tcx().sess, default_span,
 176                                     "this function's return type contains a borrowed value, but \
 177                                      there is no value for it to be borrowed from");
 178                                 span_help!(this.tcx().sess, default_span,
 179                                     "consider giving it a 'static lifetime");
 180                             } else {
 181                                 span_help!(this.tcx().sess, default_span,
 182                                     "this function's return type contains a borrowed value, but \
 183                                      the signature does not say whether it is borrowed from {}",
 184                                     m);
 185                             }
 186                         }
 187                         None => {},
 188                     }
 189                     ty::ReStatic
 190                 }
 191
 192                 Ok(rs) => rs[0],
 193             }
 194         }
 195     };
 196
 197     debug!("opt_ast_region_to_region(opt_lifetime={}) yields {}",
 198             opt_lifetime.repr(this.tcx()),
 199             r.repr(this.tcx()));
 200
 201     r
 202 }
 203
 204 fn ast_path_substs_for_ty<'tcx,AC,RS>(
 205     this: &AC,
 206     rscope: &RS,
 207     decl_def_id: ast::DefId,
 208     decl_generics: &ty::Generics<'tcx>,
 209     self_ty: Option<Ty<'tcx>>,
 210     path: &ast::Path)
 211     -> Substs<'tcx>
 212     where AC: AstConv<'tcx>, RS: RegionScope
 213 {
 214     /*!
 215      * Given a path `path` that refers to an item `I` with the
 216      * declared generics `decl_generics`, returns an appropriate
 217      * set of substitutions for this particular reference to `I`.
 218      */
 219
 220     let tcx = this.tcx();
 221
 222     // ast_path_substs() is only called to convert paths that are
 223     // known to refer to traits, types, or structs. In these cases,
 224     // all type parameters defined for the item being referenced will
 225     // be in the TypeSpace or SelfSpace.
 226     //
 227     // Note: in the case of traits, the self parameter is also
 228     // defined, but we don't currently create a `type_param_def` for
 229     // `Self` because it is implicit.
 230     assert!(decl_generics.regions.all(|d| d.space == TypeSpace));
 231     assert!(decl_generics.types.all(|d| d.space != FnSpace));
 232
 233     let (regions, types) = match path.segments.last().unwrap().parameters {
 234         ast::AngleBracketedParameters(ref data) => {
 235             convert_angle_bracketed_parameters(this, rscope, data)
 236         }
 237         ast::ParenthesizedParameters(ref data) => {
 238             span_err!(tcx.sess, path.span, E0169,
 239                       "parenthesized parameters may only be used with a trait");
 240             (Vec::new(), convert_parenthesized_parameters(this, data))
 241         }
 242     };
 243
 244     create_substs_for_ast_path(this, rscope, path.span, decl_def_id,
 245                                decl_generics, self_ty, types, regions)
 246 }
 247
 248 fn create_substs_for_ast_path<'tcx,AC,RS>(
 249     this: &AC,
 250     rscope: &RS,
 251     span: Span,
 252     decl_def_id: ast::DefId,
 253     decl_generics: &ty::Generics<'tcx>,
 254     self_ty: Option<Ty<'tcx>>,
 255     types: Vec<Ty<'tcx>>,
 256     regions: Vec<ty::Region>)
 257     -> Substs<'tcx>
 258     where AC: AstConv<'tcx>, RS: RegionScope
 259 {
 260     let tcx = this.tcx();
 261
 262     // If the type is parameterized by the this region, then replace this
 263     // region with the current anon region binding (in other words,
 264     // whatever & would get replaced with).
 265     let expected_num_region_params = decl_generics.regions.len(TypeSpace);
 266     let supplied_num_region_params = regions.len();
 267     let regions = if expected_num_region_params == supplied_num_region_params {
 268         regions
 269     } else {
 270         let anon_regions =
 271             rscope.anon_regions(span, expected_num_region_params);
 272
 273         if supplied_num_region_params != 0 || anon_regions.is_err() {
 274             span_err!(tcx.sess, span, E0107,
 275                       "wrong number of lifetime parameters: expected {}, found {}",
 276                       expected_num_region_params, supplied_num_region_params);
 277         }
 278
 279         match anon_regions {
 280             Ok(v) => v.into_iter().collect(),
 281             Err(_) => Vec::from_fn(expected_num_region_params,
 282                                    |_| ty::ReStatic) // hokey
 283         }
 284     };
 285
 286     // Convert the type parameters supplied by the user.
 287     let ty_param_defs = decl_generics.types.get_slice(TypeSpace);
 288     let supplied_ty_param_count = types.len();
 289     let formal_ty_param_count =
 290         ty_param_defs.iter()
 291         .take_while(|x| !ty::is_associated_type(tcx, x.def_id))
 292         .count();
 293     let required_ty_param_count =
 294         ty_param_defs.iter()
 295         .take_while(|x| {
 296             x.default.is_none() &&
 297                 !ty::is_associated_type(tcx, x.def_id)
 298         })
 299         .count();
 300     if supplied_ty_param_count < required_ty_param_count {
 301         let expected = if required_ty_param_count < formal_ty_param_count {
 302             "expected at least"
 303         } else {
 304             "expected"
 305         };
 306         this.tcx().sess.span_fatal(span,
 307                                    format!("wrong number of type arguments: {} {}, found {}",
 308                                            expected,
 309                                            required_ty_param_count,
 310                                            supplied_ty_param_count).as_slice());
 311     } else if supplied_ty_param_count > formal_ty_param_count {
 312         let expected = if required_ty_param_count < formal_ty_param_count {
 313             "expected at most"
 314         } else {
 315             "expected"
 316         };
 317         this.tcx().sess.span_fatal(span,
 318                                    format!("wrong number of type arguments: {} {}, found {}",
 319                                            expected,
 320                                            formal_ty_param_count,
 321                                            supplied_ty_param_count).as_slice());
 322     }
 323
 324     if supplied_ty_param_count > required_ty_param_count
 325         && !this.tcx().sess.features.borrow().default_type_params {
 326         span_err!(this.tcx().sess, span, E0108,
 327             "default type parameters are experimental and possibly buggy");
 328         span_help!(this.tcx().sess, span,
 329             "add #![feature(default_type_params)] to the crate attributes to enable");
 330     }
 331
 332     let mut substs = Substs::new_type(types, regions);
 333
 334     match self_ty {
 335         None => {
 336             // If no self-type is provided, it's still possible that
 337             // one was declared, because this could be an object type.
 338         }
 339         Some(ty) => {
 340             // If a self-type is provided, one should have been
 341             // "declared" (in other words, this should be a
 342             // trait-ref).
 343             assert!(decl_generics.types.get_self().is_some());
 344             substs.types.push(SelfSpace, ty);
 345         }
 346     }
 347
 348     for param in ty_param_defs[supplied_ty_param_count..].iter() {
 349         match param.default {
 350             Some(default) => {
 351                 // This is a default type parameter.
 352                 let default = default.subst_spanned(tcx,
 353                                                     &substs,
 354                                                     Some(span));
 355                 substs.types.push(TypeSpace, default);
 356             }
 357             None => {
 358                 tcx.sess.span_bug(span, "extra parameter without default");
 359             }
 360         }
 361     }
 362
 363     for param in decl_generics.types.get_slice(AssocSpace).iter() {
 364         substs.types.push(
 365             AssocSpace,
 366             this.associated_type_binding(span,
 367                                          self_ty,
 368                                          decl_def_id,
 369                                          param.def_id));
 370     }
 371
 372     return substs;
 373 }
 374
 375 fn convert_angle_bracketed_parameters<'tcx, AC, RS>(this: &AC,
 376                                                     rscope: &RS,
 377                                                     data: &ast::AngleBracketedParameterData)
 378                                                     -> (Vec<ty::Region>, Vec<Ty<'tcx>>)
 379     where AC: AstConv<'tcx>, RS: RegionScope
 380 {
 381     let regions: Vec<_> =
 382         data.lifetimes.iter()
 383         .map(|l| ast_region_to_region(this.tcx(), l))
 384         .collect();
 385
 386     let types: Vec<_> =
 387         data.types.iter()
 388         .map(|t| ast_ty_to_ty(this, rscope, &**t))
 389         .collect();
 390
 391     (regions, types)
 392 }
 393
 394 fn convert_parenthesized_parameters<'tcx,AC>(this: &AC,
 395                                              data: &ast::ParenthesizedParameterData)
 396                                              -> Vec<Ty<'tcx>>
 397     where AC: AstConv<'tcx>
 398 {
 399     let binding_rscope = BindingRscope::new();
 400
 401     let inputs = data.inputs.iter()
 402                             .map(|a_t| ast_ty_to_ty(this, &binding_rscope, &**a_t))
 403                             .collect();
 404     let input_ty = ty::mk_tup(this.tcx(), inputs);
 405
 406     let output = match data.output {
 407         Some(ref output_ty) => ast_ty_to_ty(this, &binding_rscope, &**output_ty),
 408         None => ty::mk_nil(this.tcx()),
 409     };
 410
 411     vec![input_ty, output]
 412 }
 413
 414 pub fn instantiate_poly_trait_ref<'tcx,AC,RS>(
 415     this: &AC,
 416     rscope: &RS,
 417     ast_trait_ref: &ast::PolyTraitRef,
 418     self_ty: Option<Ty<'tcx>>)
 419     -> Rc<ty::TraitRef<'tcx>>
 420     where AC: AstConv<'tcx>, RS: RegionScope
 421 {
 422     instantiate_trait_ref(this, rscope, &ast_trait_ref.trait_ref, self_ty)
 423 }
 424
 425 pub fn instantiate_trait_ref<'tcx,AC,RS>(this: &AC,
 426                                          rscope: &RS,
 427                                          ast_trait_ref: &ast::TraitRef,
 428                                          self_ty: Option<Ty<'tcx>>)
 429                                          -> Rc<ty::TraitRef<'tcx>>
 430                                          where AC: AstConv<'tcx>,
 431                                                RS: RegionScope
 432 {
 433     /*!
 434      * Instantiates the path for the given trait reference, assuming that
 435      * it's bound to a valid trait type. Returns the def_id for the defining
 436      * trait. Fails if the type is a type other than a trait type.
 437      */
 438
 439     match lookup_def_tcx(this.tcx(),
 440                          ast_trait_ref.path.span,
 441                          ast_trait_ref.ref_id) {
 442         def::DefTrait(trait_def_id) => {
 443             let trait_ref = Rc::new(ast_path_to_trait_ref(this, rscope, trait_def_id,
 444                                                           self_ty, &ast_trait_ref.path));
 445             this.tcx().trait_refs.borrow_mut().insert(ast_trait_ref.ref_id,
 446                                                       trait_ref.clone());
 447             trait_ref
 448         }
 449         _ => {
 450             this.tcx().sess.span_fatal(
 451                 ast_trait_ref.path.span,
 452                 format!("`{}` is not a trait", ast_trait_ref.path.user_string(this.tcx()))[]);
 453         }
 454     }
 455 }
 456
 457 fn ast_path_to_trait_ref<'tcx,AC,RS>(
 458     this: &AC,
 459     rscope: &RS,
 460     trait_def_id: ast::DefId,
 461     self_ty: Option<Ty<'tcx>>,
 462     path: &ast::Path)
 463     -> ty::TraitRef<'tcx>
 464     where AC: AstConv<'tcx>, RS: RegionScope
 465 {
 466     let trait_def = this.get_trait_def(trait_def_id);
 467
 468     // the trait reference introduces a binding level here, so
 469     // we need to shift the `rscope`. It'd be nice if we could
 470     // do away with this rscope stuff and work this knowledge
 471     // into resolve_lifetimes, as we do with non-omitted
 472     // lifetimes. Oh well, not there yet.
 473     let shifted_rscope = ShiftedRscope::new(rscope);
 474
 475     let (regions, types) = match path.segments.last().unwrap().parameters {
 476         ast::AngleBracketedParameters(ref data) => {
 477             convert_angle_bracketed_parameters(this, &shifted_rscope, data)
 478         }
 479         ast::ParenthesizedParameters(ref data) => {
 480             (Vec::new(), convert_parenthesized_parameters(this, data))
 481         }
 482     };
 483
 484     let substs = create_substs_for_ast_path(this,
 485                                             &shifted_rscope,
 486                                             path.span,
 487                                             trait_def_id,
 488                                             &trait_def.generics,
 489                                             self_ty,
 490                                             types,
 491                                             regions);
 492
 493     ty::TraitRef::new(trait_def_id, substs)
 494 }
 495
 496 pub fn ast_path_to_ty<'tcx, AC: AstConv<'tcx>, RS: RegionScope>(
 497     this: &AC,
 498     rscope: &RS,
 499     did: ast::DefId,
 500     path: &ast::Path)
 501     -> TypeAndSubsts<'tcx>
 502 {
 503     let tcx = this.tcx();
 504     let ty::Polytype {
 505         generics,
 506         ty: decl_ty
 507     } = this.get_item_ty(did);
 508
 509     let substs = ast_path_substs_for_ty(this,
 510                                         rscope,
 511                                         did,
 512                                         &generics,
 513                                         None,
 514                                         path);
 515     let ty = decl_ty.subst(tcx, &substs);
 516     TypeAndSubsts { substs: substs, ty: ty }
 517 }
 518
 519 /// Returns the type that this AST path refers to. If the path has no type
 520 /// parameters and the corresponding type has type parameters, fresh type
 521 /// and/or region variables are substituted.
 522 ///
 523 /// This is used when checking the constructor in struct literals.
 524 pub fn ast_path_to_ty_relaxed<'tcx,AC,RS>(
 525     this: &AC,
 526     rscope: &RS,
 527     did: ast::DefId,
 528     path: &ast::Path)
 529     -> TypeAndSubsts<'tcx>
 530     where AC : AstConv<'tcx>, RS : RegionScope
 531 {
 532     let tcx = this.tcx();
 533     let ty::Polytype {
 534         generics,
 535         ty: decl_ty
 536     } = this.get_item_ty(did);
 537
 538     let wants_params =
 539         generics.has_type_params(TypeSpace) || generics.has_region_params(TypeSpace);
 540
 541     let needs_defaults =
 542         wants_params &&
 543         path.segments.iter().all(|s| s.parameters.is_empty());
 544
 545     let substs = if needs_defaults {
 546         let type_params = Vec::from_fn(generics.types.len(TypeSpace),
 547                                        |_| this.ty_infer(path.span));
 548         let region_params =
 549             rscope.anon_regions(path.span, generics.regions.len(TypeSpace))
 550                   .unwrap();
 551         Substs::new(VecPerParamSpace::params_from_type(type_params),
 552                     VecPerParamSpace::params_from_type(region_params))
 553     } else {
 554         ast_path_substs_for_ty(this, rscope, did, &generics, None, path)
 555     };
 556
 557     let ty = decl_ty.subst(tcx, &substs);
 558     TypeAndSubsts {
 559         substs: substs,
 560         ty: ty,
 561     }
 562 }
 563
 564 pub const NO_REGIONS: uint = 1;
 565 pub const NO_TPS: uint = 2;
 566
 567 fn check_path_args(tcx: &ty::ctxt,
 568                    path: &ast::Path,
 569                    flags: uint) {
 570     if (flags & NO_TPS) != 0u {
 571         if path.segments.iter().any(|s| s.parameters.has_types()) {
 572             span_err!(tcx.sess, path.span, E0109,
 573                 "type parameters are not allowed on this type");
 574         }
 575     }
 576
 577     if (flags & NO_REGIONS) != 0u {
 578         if path.segments.iter().any(|s| s.parameters.has_lifetimes()) {
 579             span_err!(tcx.sess, path.span, E0110,
 580                 "region parameters are not allowed on this type");
 581         }
 582     }
 583 }
 584
 585 pub fn ast_ty_to_prim_ty<'tcx>(tcx: &ty::ctxt<'tcx>, ast_ty: &ast::Ty)
 586                                -> Option<Ty<'tcx>> {
 587     match ast_ty.node {
 588         ast::TyPath(ref path, _, id) => {
 589             let a_def = match tcx.def_map.borrow().get(&id) {
 590                 None => {
 591                     tcx.sess.span_bug(ast_ty.span,
 592                                       format!("unbound path {}",
 593                                               path.repr(tcx)).as_slice())
 594                 }
 595                 Some(&d) => d
 596             };
 597             match a_def {
 598                 def::DefPrimTy(nty) => {
 599                     match nty {
 600                         ast::TyBool => {
 601                             check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 602                             Some(ty::mk_bool())
 603                         }
 604                         ast::TyChar => {
 605                             check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 606                             Some(ty::mk_char())
 607                         }
 608                         ast::TyInt(it) => {
 609                             check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 610                             Some(ty::mk_mach_int(it))
 611                         }
 612                         ast::TyUint(uit) => {
 613                             check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 614                             Some(ty::mk_mach_uint(uit))
 615                         }
 616                         ast::TyFloat(ft) => {
 617                             check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 618                             Some(ty::mk_mach_float(ft))
 619                         }
 620                         ast::TyStr => {
 621                             Some(ty::mk_str(tcx))
 622                         }
 623                     }
 624                 }
 625                 _ => None
 626             }
 627         }
 628         _ => None
 629     }
 630 }
 631
 632 /// Converts the given AST type to a built-in type. A "built-in type" is, at
 633 /// present, either a core numeric type, a string, or `Box`.
 634 pub fn ast_ty_to_builtin_ty<'tcx, AC: AstConv<'tcx>, RS: RegionScope>(
 635         this: &AC,
 636         rscope: &RS,
 637         ast_ty: &ast::Ty)
 638         -> Option<Ty<'tcx>> {
 639     match ast_ty_to_prim_ty(this.tcx(), ast_ty) {
 640         Some(typ) => return Some(typ),
 641         None => {}
 642     }
 643
 644     match ast_ty.node {
 645         ast::TyPath(ref path, _, id) => {
 646             let a_def = match this.tcx().def_map.borrow().get(&id) {
 647                 None => {
 648                     this.tcx()
 649                         .sess
 650                         .span_bug(ast_ty.span,
 651                                   format!("unbound path {}",
 652                                           path.repr(this.tcx())).as_slice())
 653                 }
 654                 Some(&d) => d
 655             };
 656
 657             // FIXME(#12938): This is a hack until we have full support for
 658             // DST.
 659             match a_def {
 660                 def::DefTy(did, _) |
 661                 def::DefStruct(did) if Some(did) == this.tcx().lang_items.owned_box() => {
 662                     let ty = ast_path_to_ty(this, rscope, did, path).ty;
 663                     match ty.sty {
 664                         ty::ty_struct(struct_def_id, ref substs) => {
 665                             assert_eq!(struct_def_id, did);
 666                             assert_eq!(substs.types.len(TypeSpace), 1);
 667                             let referent_ty = *substs.types.get(TypeSpace, 0);
 668                             Some(ty::mk_uniq(this.tcx(), referent_ty))
 669                         }
 670                         _ => {
 671                             this.tcx().sess.span_bug(
 672                                 path.span,
 673                                 format!("converting `Box` to `{}`",
 674                                         ty.repr(this.tcx()))[]);
 675                         }
 676                     }
 677                 }
 678                 _ => None
 679             }
 680         }
 681         _ => None
 682     }
 683 }
 684
 685 // Handle `~`, `Box`, and `&` being able to mean strs and vecs.
 686 // If a_seq_ty is a str or a vec, make it a str/vec.
 687 // Also handle first-class trait types.
 688 fn mk_pointer<'tcx, AC: AstConv<'tcx>, RS: RegionScope>(
 689         this: &AC,
 690         rscope: &RS,
 691         a_seq_mutbl: ast::Mutability,
 692         a_seq_ty: &ast::Ty,
 693         region: ty::Region,
 694         constr: |Ty<'tcx>| -> Ty<'tcx>)
 695         -> Ty<'tcx>
 696 {
 697     let tcx = this.tcx();
 698
 699     debug!("mk_pointer(region={}, a_seq_ty={})",
 700            region,
 701            a_seq_ty.repr(tcx));
 702
 703     match a_seq_ty.node {
 704         ast::TyVec(ref ty) => {
 705             let ty = ast_ty_to_ty(this, rscope, &**ty);
 706             return constr(ty::mk_vec(tcx, ty, None));
 707         }
 708         ast::TyPath(ref path, ref opt_bounds, id) => {
 709             // Note that the "bounds must be empty if path is not a trait"
 710             // restriction is enforced in the below case for ty_path, which
 711             // will run after this as long as the path isn't a trait.
 712             match tcx.def_map.borrow().get(&id) {
 713                 Some(&def::DefPrimTy(ast::TyStr)) => {
 714                     check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 715                     return ty::mk_str_slice(tcx, region, a_seq_mutbl);
 716                 }
 717                 Some(&def::DefTrait(trait_def_id)) => {
 718                     let result = ast_path_to_trait_ref(this,
 719                                                        rscope,
 720                                                        trait_def_id,
 721                                                        None,
 722                                                        path);
 723                     let empty_vec = [];
 724                     let bounds = match *opt_bounds { None => empty_vec.as_slice(),
 725                                                      Some(ref bounds) => bounds.as_slice() };
 726                     let existential_bounds = conv_existential_bounds(this,
 727                                                                      rscope,
 728                                                                      path.span,
 729                                                                      &[Rc::new(result.clone())],
 730                                                                      bounds);
 731                     let tr = ty::mk_trait(tcx,
 732                                           result,
 733                                           existential_bounds);
 734                     return ty::mk_rptr(tcx, region, ty::mt{mutbl: a_seq_mutbl, ty: tr});
 735                 }
 736                 _ => {}
 737             }
 738         }
 739         _ => {}
 740     }
 741
 742     constr(ast_ty_to_ty(this, rscope, a_seq_ty))
 743 }
 744
 745 fn qpath_to_ty<'tcx,AC,RS>(this: &AC,
 746                            rscope: &RS,
 747                            ast_ty: &ast::Ty, // the TyQPath
 748                            qpath: &ast::QPath)
 749                            -> Ty<'tcx>
 750     where AC: AstConv<'tcx>, RS: RegionScope
 751 {
 752     debug!("qpath_to_ty(ast_ty={})",
 753            ast_ty.repr(this.tcx()));
 754
 755     let self_type = ast_ty_to_ty(this, rscope, &*qpath.self_type);
 756
 757     debug!("qpath_to_ty: self_type={}", self_type.repr(this.tcx()));
 758
 759     let trait_ref = instantiate_trait_ref(this,
 760                                           rscope,
 761                                           &*qpath.trait_ref,
 762                                           Some(self_type));
 763
 764     debug!("qpath_to_ty: trait_ref={}", trait_ref.repr(this.tcx()));
 765
 766     let trait_def = this.get_trait_def(trait_ref.def_id);
 767
 768     for ty_param_def in trait_def.generics.types.get_slice(AssocSpace).iter() {
 769         if ty_param_def.name == qpath.item_name.name {
 770             debug!("qpath_to_ty: corresponding ty_param_def={}", ty_param_def);
 771             return trait_ref.substs.type_for_def(ty_param_def);
 772         }
 773     }
 774
 775     this.tcx().sess.span_bug(ast_ty.span,
 776                              "this associated type didn't get added \
 777                               as a parameter for some reason")
 778 }
 779
 780 // Parses the programmer's textual representation of a type into our
 781 // internal notion of a type.
 782 pub fn ast_ty_to_ty<'tcx, AC: AstConv<'tcx>, RS: RegionScope>(
 783         this: &AC, rscope: &RS, ast_ty: &ast::Ty) -> Ty<'tcx>
 784 {
 785     debug!("ast_ty_to_ty(ast_ty={})",
 786            ast_ty.repr(this.tcx()));
 787
 788     let tcx = this.tcx();
 789
 790     let mut ast_ty_to_ty_cache = tcx.ast_ty_to_ty_cache.borrow_mut();
 791     match ast_ty_to_ty_cache.get(&ast_ty.id) {
 792         Some(&ty::atttce_resolved(ty)) => return ty,
 793         Some(&ty::atttce_unresolved) => {
 794             tcx.sess.span_fatal(ast_ty.span,
 795                                 "illegal recursive type; insert an enum \
 796                                  or struct in the cycle, if this is \
 797                                  desired");
 798         }
 799         None => { /* go on */ }
 800     }
 801     ast_ty_to_ty_cache.insert(ast_ty.id, ty::atttce_unresolved);
 802     drop(ast_ty_to_ty_cache);
 803
 804     let typ = ast_ty_to_builtin_ty(this, rscope, ast_ty).unwrap_or_else(|| {
 805         match ast_ty.node {
 806             ast::TyVec(ref ty) => {
 807                 ty::mk_vec(tcx, ast_ty_to_ty(this, rscope, &**ty), None)
 808             }
 809             ast::TyPtr(ref mt) => {
 810                 ty::mk_ptr(tcx, ty::mt {
 811                     ty: ast_ty_to_ty(this, rscope, &*mt.ty),
 812                     mutbl: mt.mutbl
 813                 })
 814             }
 815             ast::TyRptr(ref region, ref mt) => {
 816                 let r = opt_ast_region_to_region(this, rscope, ast_ty.span, region);
 817                 debug!("ty_rptr r={}", r.repr(this.tcx()));
 818                 mk_pointer(this, rscope, mt.mutbl, &*mt.ty, r,
 819                            |ty| ty::mk_rptr(tcx, r, ty::mt {ty: ty, mutbl: mt.mutbl}))
 820             }
 821             ast::TyTup(ref fields) => {
 822                 let flds = fields.iter()
 823                                  .map(|t| ast_ty_to_ty(this, rscope, &**t))
 824                                  .collect();
 825                 ty::mk_tup(tcx, flds)
 826             }
 827             ast::TyParen(ref typ) => ast_ty_to_ty(this, rscope, &**typ),
 828             ast::TyBareFn(ref bf) => {
 829                 if bf.decl.variadic && bf.abi != abi::C {
 830                     tcx.sess.span_err(ast_ty.span,
 831                                       "variadic function must have C calling convention");
 832                 }
 833                 ty::mk_bare_fn(tcx, ty_of_bare_fn(this, bf.fn_style, bf.abi, &*bf.decl))
 834             }
 835             ast::TyClosure(ref f) => {
 836                 // Use corresponding trait store to figure out default bounds
 837                 // if none were specified.
 838                 let bounds = conv_existential_bounds(this,
 839                                                      rscope,
 840                                                      ast_ty.span,
 841                                                      [].as_slice(),
 842                                                      f.bounds.as_slice());
 843                 let fn_decl = ty_of_closure(this,
 844                                             f.fn_style,
 845                                             f.onceness,
 846                                             bounds,
 847                                             ty::RegionTraitStore(
 848                                                 bounds.region_bound,
 849                                                 ast::MutMutable),
 850                                             &*f.decl,
 851                                             abi::Rust,
 852                                             None);
 853                 ty::mk_closure(tcx, fn_decl)
 854             }
 855             ast::TyProc(ref f) => {
 856                 // Use corresponding trait store to figure out default bounds
 857                 // if none were specified.
 858                 let bounds = conv_existential_bounds(this, rscope,
 859                                                      ast_ty.span,
 860                                                      [].as_slice(),
 861                                                      f.bounds.as_slice());
 862
 863                 let fn_decl = ty_of_closure(this,
 864                                             f.fn_style,
 865                                             f.onceness,
 866                                             bounds,
 867                                             ty::UniqTraitStore,
 868                                             &*f.decl,
 869                                             abi::Rust,
 870                                             None);
 871
 872                 ty::mk_closure(tcx, fn_decl)
 873             }
 874             ast::TyPolyTraitRef(ref bounds) => {
 875                 conv_ty_poly_trait_ref(this, rscope, ast_ty.span, bounds.as_slice())
 876             }
 877             ast::TyPath(ref path, ref bounds, id) => {
 878                 let a_def = match tcx.def_map.borrow().get(&id) {
 879                     None => {
 880                         tcx.sess
 881                            .span_bug(ast_ty.span,
 882                                      format!("unbound path {}",
 883                                              path.repr(tcx)).as_slice())
 884                     }
 885                     Some(&d) => d
 886                 };
 887                 // Kind bounds on path types are only supported for traits.
 888                 match a_def {
 889                     // But don't emit the error if the user meant to do a trait anyway.
 890                     def::DefTrait(..) => { },
 891                     _ if bounds.is_some() =>
 892                         tcx.sess.span_err(ast_ty.span,
 893                                           "kind bounds can only be used on trait types"),
 894                     _ => { },
 895                 }
 896                 match a_def {
 897                     def::DefTrait(trait_def_id) => {
 898                         let result = ast_path_to_trait_ref(this,
 899                                                            rscope,
 900                                                            trait_def_id,
 901                                                            None,
 902                                                            path);
 903                         let empty_bounds: &[ast::TyParamBound] = &[];
 904                         let ast_bounds = match *bounds {
 905                             Some(ref b) => b.as_slice(),
 906                             None => empty_bounds
 907                         };
 908                         let bounds = conv_existential_bounds(this,
 909                                                              rscope,
 910                                                              ast_ty.span,
 911                                                              &[Rc::new(result.clone())],
 912                                                              ast_bounds);
 913                         let result_ty = ty::mk_trait(tcx, result, bounds);
 914                         debug!("ast_ty_to_ty: result_ty={}", result_ty.repr(this.tcx()));
 915                         result_ty
 916                     }
 917                     def::DefTy(did, _) | def::DefStruct(did) => {
 918                         ast_path_to_ty(this, rscope, did, path).ty
 919                     }
 920                     def::DefTyParam(space, id, n) => {
 921                         check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 922                         ty::mk_param(tcx, space, n, id)
 923                     }
 924                     def::DefSelfTy(id) => {
 925                         // n.b.: resolve guarantees that the this type only appears in a
 926                         // trait, which we rely upon in various places when creating
 927                         // substs
 928                         check_path_args(tcx, path, NO_TPS | NO_REGIONS);
 929                         let did = ast_util::local_def(id);
 930                         ty::mk_self_type(tcx, did)
 931                     }
 932                     def::DefMod(id) => {
 933                         tcx.sess.span_fatal(ast_ty.span,
 934                             format!("found module name used as a type: {}",
 935                                     tcx.map.node_to_string(id.node)).as_slice());
 936                     }
 937                     def::DefPrimTy(_) => {
 938                         panic!("DefPrimTy arm missed in previous ast_ty_to_prim_ty call");
 939                     }
 940                     def::DefAssociatedTy(trait_type_id) => {
 941                         let path_str = tcx.map.path_to_string(
 942                             tcx.map.get_parent(trait_type_id.node));
 943                         tcx.sess.span_err(ast_ty.span,
 944                                           format!("ambiguous associated \
 945                                                    type; specify the type \
 946                                                    using the syntax `<Type \
 947                                                    as {}>::{}`",
 948                                                   path_str,
 949                                                   token::get_ident(
 950                                                       path.segments
 951                                                           .last()
 952                                                           .unwrap()
 953                                                           .identifier)
 954                                                   .get()).as_slice());
 955                         ty::mk_err()
 956                     }
 957                     _ => {
 958                         tcx.sess.span_fatal(ast_ty.span,
 959                                             format!("found value name used \
 960                                                      as a type: {}",
 961                                                     a_def).as_slice());
 962                     }
 963                 }
 964             }
 965             ast::TyQPath(ref qpath) => {
 966                 qpath_to_ty(this, rscope, ast_ty, &**qpath)
 967             }
 968             ast::TyFixedLengthVec(ref ty, ref e) => {
 969                 match const_eval::eval_const_expr_partial(tcx, &**e) {
 970                     Ok(ref r) => {
 971                         match *r {
 972                             const_eval::const_int(i) =>
 973                                 ty::mk_vec(tcx, ast_ty_to_ty(this, rscope, &**ty),
 974                                            Some(i as uint)),
 975                             const_eval::const_uint(i) =>
 976                                 ty::mk_vec(tcx, ast_ty_to_ty(this, rscope, &**ty),
 977                                            Some(i as uint)),
 978                             _ => {
 979                                 tcx.sess.span_fatal(
 980                                     ast_ty.span, "expected constant expr for array length");
 981                             }
 982                         }
 983                     }
 984                     Err(ref r) => {
 985                         tcx.sess.span_fatal(
 986                             ast_ty.span,
 987                             format!("expected constant expr for array \
 988                                      length: {}",
 989                                     *r).as_slice());
 990                     }
 991                 }
 992             }
 993             ast::TyTypeof(ref _e) => {
 994                 tcx.sess.span_bug(ast_ty.span, "typeof is reserved but unimplemented");
 995             }
 996             ast::TyInfer => {
 997                 // TyInfer also appears as the type of arguments or return
 998                 // values in a ExprClosure or ExprProc, or as
 999                 // the type of local variables. Both of these cases are
1000                 // handled specially and will not descend into this routine.
1001                 this.ty_infer(ast_ty.span)
1002             }
1003         }
1004     });
1005
1006     tcx.ast_ty_to_ty_cache.borrow_mut().insert(ast_ty.id, ty::atttce_resolved(typ));
1007     return typ;
1008 }
1009
1010 pub fn ty_of_arg<'tcx, AC: AstConv<'tcx>, RS: RegionScope>(this: &AC, rscope: &RS,
1011                                                            a: &ast::Arg,
1012                                                            expected_ty: Option<Ty<'tcx>>)
1013                                                            -> Ty<'tcx> {
1014     match a.ty.node {
1015         ast::TyInfer if expected_ty.is_some() => expected_ty.unwrap(),
1016         ast::TyInfer => this.ty_infer(a.ty.span),
1017         _ => ast_ty_to_ty(this, rscope, &*a.ty),
1018     }
1019 }
1020
1021 struct SelfInfo<'a, 'tcx> {
1022     untransformed_self_ty: Ty<'tcx>,
1023     explicit_self: &'a ast::ExplicitSelf,
1024 }
1025
1026 pub fn ty_of_method<'tcx, AC: AstConv<'tcx>>(
1027                     this: &AC,
1028                     fn_style: ast::FnStyle,
1029                     untransformed_self_ty: Ty<'tcx>,
1030                     explicit_self: &ast::ExplicitSelf,
1031                     decl: &ast::FnDecl,
1032                     abi: abi::Abi)
1033                     -> (ty::BareFnTy<'tcx>, ty::ExplicitSelfCategory) {
1034     let self_info = Some(SelfInfo {
1035         untransformed_self_ty: untransformed_self_ty,
1036         explicit_self: explicit_self,
1037     });
1038     let (bare_fn_ty, optional_explicit_self_category) =
1039         ty_of_method_or_bare_fn(this,
1040                                 fn_style,
1041                                 abi,
1042                                 self_info,
1043                                 decl);
1044     (bare_fn_ty, optional_explicit_self_category.unwrap())
1045 }
1046
1047 pub fn ty_of_bare_fn<'tcx, AC: AstConv<'tcx>>(this: &AC, fn_style: ast::FnStyle, abi: abi::Abi,
1048                                               decl: &ast::FnDecl) -> ty::BareFnTy<'tcx> {
1049     let (bare_fn_ty, _) = ty_of_method_or_bare_fn(this, fn_style, abi, None, decl);
1050     bare_fn_ty
1051 }
1052
1053 fn ty_of_method_or_bare_fn<'a, 'tcx, AC: AstConv<'tcx>>(
1054                            this: &AC,
1055                            fn_style: ast::FnStyle,
1056                            abi: abi::Abi,
1057                            opt_self_info: Option<SelfInfo<'a, 'tcx>>,
1058                            decl: &ast::FnDecl)
1059                            -> (ty::BareFnTy<'tcx>,
1060                                Option<ty::ExplicitSelfCategory>) {
1061     debug!("ty_of_method_or_bare_fn");
1062
1063     // New region names that appear inside of the arguments of the function
1064     // declaration are bound to that function type.
1065     let rb = rscope::BindingRscope::new();
1066
1067     // `implied_output_region` is the region that will be assumed for any
1068     // region parameters in the return type. In accordance with the rules for
1069     // lifetime elision, we can determine it in two ways. First (determined
1070     // here), if self is by-reference, then the implied output region is the
1071     // region of the self parameter.
1072     let mut explicit_self_category_result = None;
1073     let (self_ty, mut implied_output_region) = match opt_self_info {
1074         None => (None, None),
1075         Some(self_info) => {
1076             // Figure out and record the explicit self category.
1077             let explicit_self_category =
1078                 determine_explicit_self_category(this, &rb, &self_info);
1079             explicit_self_category_result = Some(explicit_self_category);
1080             match explicit_self_category {
1081                 ty::StaticExplicitSelfCategory => {
1082                     (None, None)
1083                 }
1084                 ty::ByValueExplicitSelfCategory => {
1085                     (Some(self_info.untransformed_self_ty), None)
1086                 }
1087                 ty::ByReferenceExplicitSelfCategory(region, mutability) => {
1088                     (Some(ty::mk_rptr(this.tcx(),
1089                                       region,
1090                                       ty::mt {
1091                                         ty: self_info.untransformed_self_ty,
1092                                         mutbl: mutability
1093                                       })),
1094                      Some(region))
1095                 }
1096                 ty::ByBoxExplicitSelfCategory => {
1097                     (Some(ty::mk_uniq(this.tcx(),
1098                                       self_info.untransformed_self_ty)),
1099                      None)
1100                 }
1101             }
1102         }
1103     };
1104
1105     // HACK(eddyb) replace the fake self type in the AST with the actual type.
1106     let input_params = if self_ty.is_some() {
1107         decl.inputs.slice_from(1)
1108     } else {
1109         decl.inputs.as_slice()
1110     };
1111     let input_tys = input_params.iter().map(|a| ty_of_arg(this, &rb, a, None));
1112     let input_pats: Vec<String> = input_params.iter()
1113                                               .map(|a| pprust::pat_to_string(&*a.pat))
1114                                               .collect();
1115     let self_and_input_tys: Vec<Ty> =
1116         self_ty.into_iter().chain(input_tys).collect();
1117
1118     let mut lifetimes_for_params: Vec<(String, Vec<ty::Region>)> = Vec::new();
1119
1120     // Second, if there was exactly one lifetime (either a substitution or a
1121     // reference) in the arguments, then any anonymous regions in the output
1122     // have that lifetime.
1123     if implied_output_region.is_none() {
1124         let mut self_and_input_tys_iter = self_and_input_tys.iter();
1125         if self_ty.is_some() {
1126             // Skip the first argument if `self` is present.
1127             drop(self_and_input_tys_iter.next())
1128         }
1129
1130         for (input_type, input_pat) in self_and_input_tys_iter.zip(input_pats.into_iter()) {
1131             let mut accumulator = Vec::new();
1132             ty::accumulate_lifetimes_in_type(&mut accumulator, *input_type);
1133             lifetimes_for_params.push((input_pat, accumulator));
1134         }
1135
1136         if lifetimes_for_params.iter().map(|&(_, ref x)| x.len()).sum() == 1 {
1137             implied_output_region =
1138                 Some(lifetimes_for_params.iter()
1139                                          .filter_map(|&(_, ref x)|
1140                                             if x.len() == 1 { Some(x[0]) } else { None })
1141                                          .next().unwrap());
1142         }
1143     }
1144
1145     let param_lifetimes: Vec<(String, uint)> = lifetimes_for_params.into_iter()
1146                                                                    .map(|(n, v)| (n, v.len()))
1147                                                                    .filter(|&(_, l)| l != 0)
1148                                                                    .collect();
1149
1150     let output_ty = match decl.output {
1151         ast::Return(ref output) if output.node == ast::TyInfer =>
1152             ty::FnConverging(this.ty_infer(output.span)),
1153         ast::Return(ref output) =>
1154             ty::FnConverging(match implied_output_region {
1155                 Some(implied_output_region) => {
1156                     let rb = SpecificRscope::new(implied_output_region);
1157                     ast_ty_to_ty(this, &rb, &**output)
1158                 }
1159                 None => {
1160                     // All regions must be explicitly specified in the output
1161                     // if the lifetime elision rules do not apply. This saves
1162                     // the user from potentially-confusing errors.
1163                     let rb = UnelidableRscope::new(param_lifetimes);
1164                     ast_ty_to_ty(this, &rb, &**output)
1165                 }
1166             }),
1167         ast::NoReturn(_) => ty::FnDiverging
1168     };
1169
1170     (ty::BareFnTy {
1171         fn_style: fn_style,
1172         abi: abi,
1173         sig: ty::FnSig {
1174             inputs: self_and_input_tys,
1175             output: output_ty,
1176             variadic: decl.variadic
1177         }
1178     }, explicit_self_category_result)
1179 }
1180
1181 fn determine_explicit_self_category<'a, 'tcx, AC: AstConv<'tcx>,
1182                                     RS:RegionScope>(
1183                                     this: &AC,
1184                                     rscope: &RS,
1185                                     self_info: &SelfInfo<'a, 'tcx>)
1186                                     -> ty::ExplicitSelfCategory
1187 {
1188     return match self_info.explicit_self.node {
1189         ast::SelfStatic => ty::StaticExplicitSelfCategory,
1190         ast::SelfValue(_) => ty::ByValueExplicitSelfCategory,
1191         ast::SelfRegion(ref lifetime, mutability, _) => {
1192             let region =
1193                 opt_ast_region_to_region(this,
1194                                          rscope,
1195                                          self_info.explicit_self.span,
1196                                          lifetime);
1197             ty::ByReferenceExplicitSelfCategory(region, mutability)
1198         }
1199         ast::SelfExplicit(ref ast_type, _) => {
1200             let explicit_type = ast_ty_to_ty(this, rscope, &**ast_type);
1201
1202             // We wish to (for now) categorize an explicit self
1203             // declaration like `self: SomeType` into either `self`,
1204             // `&self`, `&mut self`, or `Box<self>`. We do this here
1205             // by some simple pattern matching. A more precise check
1206             // is done later in `check_method_self_type()`.
1207             //
1208             // Examples:
1209             //
1210             // ```
1211             // impl Foo for &T {
1212             //     // Legal declarations:
1213             //     fn method1(self: &&T); // ByReferenceExplicitSelfCategory
1214             //     fn method2(self: &T); // ByValueExplicitSelfCategory
1215             //     fn method3(self: Box<&T>); // ByBoxExplicitSelfCategory
1216             //
1217             //     // Invalid cases will be caught later by `check_method_self_type`:
1218             //     fn method_err1(self: &mut T); // ByReferenceExplicitSelfCategory
1219             // }
1220             // ```
1221             //
1222             // To do the check we just count the number of "modifiers"
1223             // on each type and compare them. If they are the same or
1224             // the impl has more, we call it "by value". Otherwise, we
1225             // look at the outermost modifier on the method decl and
1226             // call it by-ref, by-box as appropriate. For method1, for
1227             // example, the impl type has one modifier, but the method
1228             // type has two, so we end up with
1229             // ByReferenceExplicitSelfCategory.
1230
1231             let impl_modifiers = count_modifiers(self_info.untransformed_self_ty);
1232             let method_modifiers = count_modifiers(explicit_type);
1233
1234             debug!("determine_explicit_self_category(self_info.untransformed_self_ty={} \
1235                    explicit_type={} \
1236                    modifiers=({},{})",
1237                    self_info.untransformed_self_ty.repr(this.tcx()),
1238                    explicit_type.repr(this.tcx()),
1239                    impl_modifiers,
1240                    method_modifiers);
1241
1242             if impl_modifiers >= method_modifiers {
1243                 ty::ByValueExplicitSelfCategory
1244             } else {
1245                 match explicit_type.sty {
1246                     ty::ty_rptr(r, mt) => ty::ByReferenceExplicitSelfCategory(r, mt.mutbl),
1247                     ty::ty_uniq(_) => ty::ByBoxExplicitSelfCategory,
1248                     _ => ty::ByValueExplicitSelfCategory,
1249                 }
1250             }
1251         }
1252     };
1253
1254     fn count_modifiers(ty: Ty) -> uint {
1255         match ty.sty {
1256             ty::ty_rptr(_, mt) => count_modifiers(mt.ty) + 1,
1257             ty::ty_uniq(t) => count_modifiers(t) + 1,
1258             _ => 0,
1259         }
1260     }
1261 }
1262
1263 pub fn ty_of_closure<'tcx, AC: AstConv<'tcx>>(
1264     this: &AC,
1265     fn_style: ast::FnStyle,
1266     onceness: ast::Onceness,
1267     bounds: ty::ExistentialBounds,
1268     store: ty::TraitStore,
1269     decl: &ast::FnDecl,
1270     abi: abi::Abi,
1271     expected_sig: Option<ty::FnSig<'tcx>>)
1272     -> ty::ClosureTy<'tcx>
1273 {
1274     debug!("ty_of_closure(expected_sig={})",
1275            expected_sig.repr(this.tcx()));
1276
1277     // new region names that appear inside of the fn decl are bound to
1278     // that function type
1279     let rb = rscope::BindingRscope::new();
1280
1281     let input_tys: Vec<_> = decl.inputs.iter().enumerate().map(|(i, a)| {
1282         let expected_arg_ty = expected_sig.as_ref().and_then(|e| {
1283             // no guarantee that the correct number of expected args
1284             // were supplied
1285             if i < e.inputs.len() {
1286                 Some(e.inputs[i])
1287             } else {
1288                 None
1289             }
1290         });
1291         ty_of_arg(this, &rb, a, expected_arg_ty)
1292     }).collect();
1293
1294     let expected_ret_ty = expected_sig.map(|e| e.output);
1295
1296     let output_ty = match decl.output {
1297         ast::Return(ref output) if output.node == ast::TyInfer && expected_ret_ty.is_some() =>
1298             expected_ret_ty.unwrap(),
1299         ast::Return(ref output) if output.node == ast::TyInfer =>
1300             ty::FnConverging(this.ty_infer(output.span)),
1301         ast::Return(ref output) =>
1302             ty::FnConverging(ast_ty_to_ty(this, &rb, &**output)),
1303         ast::NoReturn(_) => ty::FnDiverging
1304     };
1305
1306     debug!("ty_of_closure: input_tys={}", input_tys.repr(this.tcx()));
1307     debug!("ty_of_closure: output_ty={}", output_ty.repr(this.tcx()));
1308
1309     ty::ClosureTy {
1310         fn_style: fn_style,
1311         onceness: onceness,
1312         store: store,
1313         bounds: bounds,
1314         abi: abi,
1315         sig: ty::FnSig {inputs: input_tys,
1316                         output: output_ty,
1317                         variadic: decl.variadic}
1318     }
1319 }
1320
1321 pub fn conv_existential_bounds<'tcx, AC: AstConv<'tcx>, RS:RegionScope>(
1322     this: &AC,
1323     rscope: &RS,
1324     span: Span,
1325     main_trait_refs: &[Rc<ty::TraitRef<'tcx>>],
1326     ast_bounds: &[ast::TyParamBound])
1327     -> ty::ExistentialBounds
1328 {
1329     /*!
1330      * Given an existential type like `Foo+'a+Bar`, this routine
1331      * converts the `'a` and `Bar` intos an `ExistentialBounds`
1332      * struct. The `main_trait_refs` argument specifies the `Foo` --
1333      * it is absent for closures. Eventually this should all be
1334      * normalized, I think, so that there is no "main trait ref" and
1335      * instead we just have a flat list of bounds as the existential
1336      * type.
1337      */
1338
1339     let ast_bound_refs: Vec<&ast::TyParamBound> =
1340         ast_bounds.iter().collect();
1341
1342     let partitioned_bounds =
1343         partition_bounds(this.tcx(), span, ast_bound_refs.as_slice());
1344
1345     conv_existential_bounds_from_partitioned_bounds(
1346         this, rscope, span, main_trait_refs, partitioned_bounds)
1347 }
1348
1349 fn conv_ty_poly_trait_ref<'tcx, AC, RS>(
1350     this: &AC,
1351     rscope: &RS,
1352     span: Span,
1353     ast_bounds: &[ast::TyParamBound])
1354     -> Ty<'tcx>
1355     where AC: AstConv<'tcx>, RS:RegionScope
1356 {
1357     let ast_bounds: Vec<&ast::TyParamBound> = ast_bounds.iter().collect();
1358     let mut partitioned_bounds = partition_bounds(this.tcx(), span, ast_bounds[]);
1359
1360     let main_trait_bound = match partitioned_bounds.trait_bounds.remove(0) {
1361         Some(trait_bound) => {
1362             Some(instantiate_poly_trait_ref(this, rscope, trait_bound, None))
1363         }
1364         None => {
1365             this.tcx().sess.span_err(
1366                 span,
1367                 "at least one non-builtin trait is required for an object type");
1368             None
1369         }
1370     };
1371
1372     let bounds = conv_existential_bounds_from_partitioned_bounds(this,
1373                                                                  rscope,
1374                                                                  span,
1375                                                                  main_trait_bound.as_slice(),
1376                                                                  partitioned_bounds);
1377
1378     match main_trait_bound {
1379         None => ty::mk_err(),
1380         Some(principal) => ty::mk_trait(this.tcx(), (*principal).clone(), bounds)
1381     }
1382 }
1383
1384 pub fn conv_existential_bounds_from_partitioned_bounds<'tcx, AC, RS>(
1385     this: &AC,
1386     rscope: &RS,
1387     span: Span,
1388     main_trait_refs: &[Rc<ty::TraitRef<'tcx>>],
1389     partitioned_bounds: PartitionedBounds)
1390     -> ty::ExistentialBounds
1391     where AC: AstConv<'tcx>, RS:RegionScope
1392 {
1393     let PartitionedBounds { builtin_bounds,
1394                             trait_bounds,
1395                             region_bounds } =
1396         partitioned_bounds;
1397
1398     if !trait_bounds.is_empty() {
1399         let b = &trait_bounds[0];
1400         this.tcx().sess.span_err(
1401             b.trait_ref.path.span,
1402             format!("only the builtin traits can be used \
1403                      as closure or object bounds").as_slice());
1404     }
1405
1406     // The "main trait refs", rather annoyingly, have no type
1407     // specified for the `Self` parameter of the trait. The reason for
1408     // this is that they are, after all, *existential* types, and
1409     // hence that type is unknown. However, leaving this type missing
1410     // causes the substitution code to go all awry when walking the
1411     // bounds, so here we clone those trait refs and insert ty::err as
1412     // the self type. Perhaps we should do this more generally, it'd
1413     // be convenient (or perhaps something else, i.e., ty::erased).
1414     let main_trait_refs: Vec<Rc<ty::TraitRef>> =
1415         main_trait_refs.iter()
1416         .map(|t|
1417              Rc::new(ty::TraitRef {
1418                  def_id: t.def_id,
1419                  substs: t.substs.with_self_ty(ty::mk_err()) }))
1420         .collect();
1421
1422     let region_bound = compute_region_bound(this,
1423                                             rscope,
1424                                             span,
1425                                             builtin_bounds,
1426                                             region_bounds.as_slice(),
1427                                             main_trait_refs.as_slice());
1428
1429     ty::ExistentialBounds {
1430         region_bound: region_bound,
1431         builtin_bounds: builtin_bounds,
1432     }
1433 }
1434
1435 pub fn compute_opt_region_bound<'tcx>(tcx: &ty::ctxt<'tcx>,
1436                                       span: Span,
1437                                       builtin_bounds: ty::BuiltinBounds,
1438                                       region_bounds: &[&ast::Lifetime],
1439                                       trait_bounds: &[Rc<ty::TraitRef<'tcx>>])
1440                                       -> Option<ty::Region>
1441 {
1442     /*!
1443      * Given the bounds on a type parameter / existential type,
1444      * determines what single region bound (if any) we can use to
1445      * summarize this type. The basic idea is that we will use the
1446      * bound the user provided, if they provided one, and otherwise
1447      * search the supertypes of trait bounds for region bounds. It may
1448      * be that we can derive no bound at all, in which case we return
1449      * `None`.
1450      */
1451
1452     if region_bounds.len() > 1 {
1453         tcx.sess.span_err(
1454             region_bounds[1].span,
1455             format!("only a single explicit lifetime bound is permitted").as_slice());
1456     }
1457
1458     if region_bounds.len() != 0 {
1459         // Explicitly specified region bound. Use that.
1460         let r = region_bounds[0];
1461         return Some(ast_region_to_region(tcx, r));
1462     }
1463
1464     // No explicit region bound specified. Therefore, examine trait
1465     // bounds and see if we can derive region bounds from those.
1466     let derived_region_bounds =
1467         ty::required_region_bounds(
1468             tcx,
1469             &[],
1470             builtin_bounds,
1471             trait_bounds);
1472
1473     // If there are no derived region bounds, then report back that we
1474     // can find no region bound.
1475     if derived_region_bounds.len() == 0 {
1476         return None;
1477     }
1478
1479     // If any of the derived region bounds are 'static, that is always
1480     // the best choice.
1481     if derived_region_bounds.iter().any(|r| ty::ReStatic == *r) {
1482         return Some(ty::ReStatic);
1483     }
1484
1485     // Determine whether there is exactly one unique region in the set
1486     // of derived region bounds. If so, use that. Otherwise, report an
1487     // error.
1488     let r = derived_region_bounds[0];
1489     if derived_region_bounds.slice_from(1).iter().any(|r1| r != *r1) {
1490         tcx.sess.span_err(
1491             span,
1492             format!("ambiguous lifetime bound, \
1493                      explicit lifetime bound required").as_slice());
1494     }
1495     return Some(r);
1496 }
1497
1498 fn compute_region_bound<'tcx, AC: AstConv<'tcx>, RS:RegionScope>(
1499     this: &AC,
1500     rscope: &RS,
1501     span: Span,
1502     builtin_bounds: ty::BuiltinBounds,
1503     region_bounds: &[&ast::Lifetime],
1504     trait_bounds: &[Rc<ty::TraitRef<'tcx>>])
1505     -> ty::Region
1506 {
1507     /*!
1508      * A version of `compute_opt_region_bound` for use where some
1509      * region bound is required (existential types,
1510      * basically). Reports an error if no region bound can be derived
1511      * and we are in an `rscope` that does not provide a default.
1512      */
1513
1514     match compute_opt_region_bound(this.tcx(), span, builtin_bounds,
1515                                    region_bounds, trait_bounds) {
1516         Some(r) => r,
1517         None => {
1518             match rscope.default_region_bound(span) {
1519                 Some(r) => { r }
1520                 None => {
1521                     this.tcx().sess.span_err(
1522                         span,
1523                         format!("explicit lifetime bound required").as_slice());
1524                     ty::ReStatic
1525                 }
1526             }
1527         }
1528     }
1529 }
1530
1531 pub struct PartitionedBounds<'a> {
1532     pub builtin_bounds: ty::BuiltinBounds,
1533     pub trait_bounds: Vec<&'a ast::PolyTraitRef>,
1534     pub region_bounds: Vec<&'a ast::Lifetime>,
1535 }
1536
1537 pub fn partition_bounds<'a>(tcx: &ty::ctxt,
1538                             _span: Span,
1539                             ast_bounds: &'a [&ast::TyParamBound])
1540                             -> PartitionedBounds<'a>
1541 {
1542     /*!
1543      * Divides a list of bounds from the AST into three groups:
1544      * builtin bounds (Copy, Sized etc), general trait bounds,
1545      * and region bounds.
1546      */
1547
1548     let mut builtin_bounds = ty::empty_builtin_bounds();
1549     let mut region_bounds = Vec::new();
1550     let mut trait_bounds = Vec::new();
1551     let mut trait_def_ids = DefIdMap::new();
1552     for &ast_bound in ast_bounds.iter() {
1553         match *ast_bound {
1554             ast::TraitTyParamBound(ref b) => {
1555                 match lookup_def_tcx(tcx, b.trait_ref.path.span, b.trait_ref.ref_id) {
1556                     def::DefTrait(trait_did) => {
1557                         match trait_def_ids.get(&trait_did) {
1558                             // Already seen this trait. We forbid
1559                             // duplicates in the list (for some
1560                             // reason).
1561                             Some(span) => {
1562                                 span_err!(
1563                                     tcx.sess, b.trait_ref.path.span, E0127,
1564                                     "trait `{}` already appears in the \
1565                                      list of bounds",
1566                                     b.trait_ref.path.user_string(tcx));
1567                                 tcx.sess.span_note(
1568                                     *span,
1569                                     "previous appearance is here");
1570
1571                                 continue;
1572                             }
1573
1574                             None => { }
1575                         }
1576
1577                         trait_def_ids.insert(trait_did, b.trait_ref.path.span);
1578
1579                         if ty::try_add_builtin_trait(tcx,
1580                                                      trait_did,
1581                                                      &mut builtin_bounds) {
1582                             continue; // success
1583                         }
1584                     }
1585                     _ => {
1586                         // Not a trait? that's an error, but it'll get
1587                         // reported later.
1588                     }
1589                 }
1590                 trait_bounds.push(b);
1591             }
1592             ast::RegionTyParamBound(ref l) => {
1593                 region_bounds.push(l);
1594             }
1595         }
1596     }
1597
1598     PartitionedBounds {
1599         builtin_bounds: builtin_bounds,
1600         trait_bounds: trait_bounds,
1601         region_bounds: region_bounds,
1602     }
1603 }