src/librustc/ty/flags.rs

   1 // Copyright 2012-2015 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 use mir::interpret::ConstValue;
  12 use ty::subst::Substs;
  13 use ty::{self, Ty, TypeFlags, TypeFoldable};
  14
  15 #[derive(Debug)]
  16 pub struct FlagComputation {
  17     pub flags: TypeFlags,
  18
  19     // see `TyS::outer_exclusive_binder` for details
  20     pub outer_exclusive_binder: ty::DebruijnIndex,
  21 }
  22
  23 impl FlagComputation {
  24     fn new() -> FlagComputation {
  25         FlagComputation {
  26             flags: TypeFlags::empty(),
  27             outer_exclusive_binder: ty::INNERMOST,
  28         }
  29     }
  30
  31     pub fn for_sty(st: &ty::TypeVariants) -> FlagComputation {
  32         let mut result = FlagComputation::new();
  33         result.add_sty(st);
  34         result
  35     }
  36
  37     fn add_flags(&mut self, flags: TypeFlags) {
  38         self.flags = self.flags | (flags & TypeFlags::NOMINAL_FLAGS);
  39     }
  40
  41     /// indicates that `self` refers to something at binding level `binder`
  42     fn add_binder(&mut self, binder: ty::DebruijnIndex) {
  43         let exclusive_binder = binder.shifted_in(1);
  44         self.add_exclusive_binder(exclusive_binder);
  45     }
  46
  47     /// indicates that `self` refers to something *inside* binding
  48     /// level `binder` -- not bound by `binder`, but bound by the next
  49     /// binder internal to it
  50     fn add_exclusive_binder(&mut self, exclusive_binder: ty::DebruijnIndex) {
  51         self.outer_exclusive_binder = self.outer_exclusive_binder.max(exclusive_binder);
  52     }
  53
  54     /// Adds the flags/depth from a set of types that appear within the current type, but within a
  55     /// region binder.
  56     fn add_bound_computation(&mut self, computation: &FlagComputation) {
  57         self.add_flags(computation.flags);
  58
  59         // The types that contributed to `computation` occurred within
  60         // a region binder, so subtract one from the region depth
  61         // within when adding the depth to `self`.
  62         let outer_exclusive_binder = computation.outer_exclusive_binder;
  63         if outer_exclusive_binder > ty::INNERMOST {
  64             self.add_exclusive_binder(outer_exclusive_binder.shifted_out(1));
  65         } else {
  66             // otherwise, this binder captures nothing
  67         }
  68     }
  69
  70     fn add_sty(&mut self, st: &ty::TypeVariants) {
  71         match st {
  72             &ty::TyBool |
  73             &ty::TyChar |
  74             &ty::TyInt(_) |
  75             &ty::TyFloat(_) |
  76             &ty::TyUint(_) |
  77             &ty::TyNever |
  78             &ty::TyStr |
  79             &ty::TyForeign(..) => {
  80             }
  81
  82             // You might think that we could just return TyError for
  83             // any type containing TyError as a component, and get
  84             // rid of the TypeFlags::HAS_TY_ERR flag -- likewise for ty_bot (with
  85             // the exception of function types that return bot).
  86             // But doing so caused sporadic memory corruption, and
  87             // neither I (tjc) nor nmatsakis could figure out why,
  88             // so we're doing it this way.
  89             &ty::TyError => {
  90                 self.add_flags(TypeFlags::HAS_TY_ERR)
  91             }
  92
  93             &ty::TyParam(ref p) => {
  94                 self.add_flags(TypeFlags::HAS_FREE_LOCAL_NAMES);
  95                 if p.is_self() {
  96                     self.add_flags(TypeFlags::HAS_SELF);
  97                 } else {
  98                     self.add_flags(TypeFlags::HAS_PARAMS);
  99                 }
 100             }
 101
 102             &ty::TyGenerator(_, ref substs, _) => {
 103                 self.add_flags(TypeFlags::HAS_TY_CLOSURE);
 104                 self.add_flags(TypeFlags::HAS_FREE_LOCAL_NAMES);
 105                 self.add_substs(&substs.substs);
 106             }
 107
 108             &ty::TyGeneratorWitness(ref ts) => {
 109                 let mut computation = FlagComputation::new();
 110                 computation.add_tys(&ts.skip_binder()[..]);
 111                 self.add_bound_computation(&computation);
 112             }
 113
 114             &ty::TyClosure(_, ref substs) => {
 115                 self.add_flags(TypeFlags::HAS_TY_CLOSURE);
 116                 self.add_flags(TypeFlags::HAS_FREE_LOCAL_NAMES);
 117                 self.add_substs(&substs.substs);
 118             }
 119
 120             &ty::TyInfer(infer) => {
 121                 self.add_flags(TypeFlags::HAS_FREE_LOCAL_NAMES); // it might, right?
 122                 self.add_flags(TypeFlags::HAS_TY_INFER);
 123                 match infer {
 124                     ty::FreshTy(_) |
 125                     ty::FreshIntTy(_) |
 126                     ty::FreshFloatTy(_) |
 127                     ty::CanonicalTy(_) => {
 128                         self.add_flags(TypeFlags::HAS_CANONICAL_VARS);
 129                     }
 130
 131                     ty::TyVar(_) |
 132                     ty::IntVar(_) |
 133                     ty::FloatVar(_) => {
 134                         self.add_flags(TypeFlags::KEEP_IN_LOCAL_TCX)
 135                     }
 136                 }
 137             }
 138
 139             &ty::TyAdt(_, substs) => {
 140                 self.add_substs(substs);
 141             }
 142
 143             &ty::TyProjection(ref data) => {
 144                 // currently we can't normalize projections that
 145                 // include bound regions, so track those separately.
 146                 if !data.has_escaping_regions() {
 147                     self.add_flags(TypeFlags::HAS_NORMALIZABLE_PROJECTION);
 148                 }
 149                 self.add_flags(TypeFlags::HAS_PROJECTION);
 150                 self.add_projection_ty(data);
 151             }
 152
 153             &ty::TyAnon(_, substs) => {
 154                 self.add_flags(TypeFlags::HAS_PROJECTION);
 155                 self.add_substs(substs);
 156             }
 157
 158             &ty::TyDynamic(ref obj, r) => {
 159                 let mut computation = FlagComputation::new();
 160                 for predicate in obj.skip_binder().iter() {
 161                     match *predicate {
 162                         ty::ExistentialPredicate::Trait(tr) => computation.add_substs(tr.substs),
 163                         ty::ExistentialPredicate::Projection(p) => {
 164                             let mut proj_computation = FlagComputation::new();
 165                             proj_computation.add_existential_projection(&p);
 166                             self.add_bound_computation(&proj_computation);
 167                         }
 168                         ty::ExistentialPredicate::AutoTrait(_) => {}
 169                     }
 170                 }
 171                 self.add_bound_computation(&computation);
 172                 self.add_region(r);
 173             }
 174
 175             &ty::TyArray(tt, len) => {
 176                 self.add_ty(tt);
 177                 self.add_const(len);
 178             }
 179
 180             &ty::TySlice(tt) => {
 181                 self.add_ty(tt)
 182             }
 183
 184             &ty::TyRawPtr(ref m) => {
 185                 self.add_ty(m.ty);
 186             }
 187
 188             &ty::TyRef(r, ty, _) => {
 189                 self.add_region(r);
 190                 self.add_ty(ty);
 191             }
 192
 193             &ty::TyTuple(ref ts) => {
 194                 self.add_tys(&ts[..]);
 195             }
 196
 197             &ty::TyFnDef(_, substs) => {
 198                 self.add_substs(substs);
 199             }
 200
 201             &ty::TyFnPtr(f) => {
 202                 self.add_fn_sig(f);
 203             }
 204         }
 205     }
 206
 207     fn add_ty(&mut self, ty: Ty) {
 208         self.add_flags(ty.flags);
 209         self.add_exclusive_binder(ty.outer_exclusive_binder);
 210     }
 211
 212     fn add_tys(&mut self, tys: &[Ty]) {
 213         for &ty in tys {
 214             self.add_ty(ty);
 215         }
 216     }
 217
 218     fn add_fn_sig(&mut self, fn_sig: ty::PolyFnSig) {
 219         let mut computation = FlagComputation::new();
 220
 221         computation.add_tys(fn_sig.skip_binder().inputs());
 222         computation.add_ty(fn_sig.skip_binder().output());
 223
 224         self.add_bound_computation(&computation);
 225     }
 226
 227     fn add_region(&mut self, r: ty::Region) {
 228         self.add_flags(r.type_flags());
 229         if let ty::ReLateBound(debruijn, _) = *r {
 230             self.add_binder(debruijn);
 231         }
 232     }
 233
 234     fn add_const(&mut self, constant: &ty::Const) {
 235         self.add_ty(constant.ty);
 236         if let ConstValue::Unevaluated(_, substs) = constant.val {
 237             self.add_flags(TypeFlags::HAS_PROJECTION);
 238             self.add_substs(substs);
 239         }
 240     }
 241
 242     fn add_existential_projection(&mut self, projection: &ty::ExistentialProjection) {
 243         self.add_substs(projection.substs);
 244         self.add_ty(projection.ty);
 245     }
 246
 247     fn add_projection_ty(&mut self, projection_ty: &ty::ProjectionTy) {
 248         self.add_substs(projection_ty.substs);
 249     }
 250
 251     fn add_substs(&mut self, substs: &Substs) {
 252         for ty in substs.types() {
 253             self.add_ty(ty);
 254         }
 255
 256         for r in substs.regions() {
 257             self.add_region(r);
 258         }
 259     }
 260 }