src/librustc_middle/ty/flags.rs

   1 use crate::ty::subst::{GenericArg, GenericArgKind};
   2 use crate::ty::{self, InferConst, Ty, TypeFlags};
   3 use std::slice;
   4
   5 #[derive(Debug)]
   6 pub struct FlagComputation {
   7     pub flags: TypeFlags,
   8
   9     // see `TyS::outer_exclusive_binder` for details
  10     pub outer_exclusive_binder: ty::DebruijnIndex,
  11 }
  12
  13 impl FlagComputation {
  14     fn new() -> FlagComputation {
  15         FlagComputation { flags: TypeFlags::empty(), outer_exclusive_binder: ty::INNERMOST }
  16     }
  17
  18     #[allow(rustc::usage_of_ty_tykind)]
  19     pub fn for_kind(kind: &ty::TyKind<'_>) -> FlagComputation {
  20         let mut result = FlagComputation::new();
  21         result.add_kind(kind);
  22         result
  23     }
  24
  25     pub fn for_predicate(kind: &ty::PredicateKind<'_>) -> FlagComputation {
  26         let mut result = FlagComputation::new();
  27         result.add_predicate_kind(kind);
  28         result
  29     }
  30
  31     pub fn for_const(c: &ty::Const<'_>) -> TypeFlags {
  32         let mut result = FlagComputation::new();
  33         result.add_const(c);
  34         result.flags
  35     }
  36
  37     fn add_flags(&mut self, flags: TypeFlags) {
  38         self.flags = self.flags | flags;
  39     }
  40
  41     /// indicates that `self` refers to something at binding level `binder`
  42     fn add_bound_var(&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         } // otherwise, this binder captures nothing
  66     }
  67
  68     #[allow(rustc::usage_of_ty_tykind)]
  69     fn add_kind(&mut self, kind: &ty::TyKind<'_>) {
  70         match kind {
  71             &ty::Bool
  72             | &ty::Char
  73             | &ty::Int(_)
  74             | &ty::Float(_)
  75             | &ty::Uint(_)
  76             | &ty::Never
  77             | &ty::Str
  78             | &ty::Foreign(..) => {}
  79
  80             &ty::Error(_) => self.add_flags(TypeFlags::HAS_ERROR),
  81
  82             &ty::Param(_) => {
  83                 self.add_flags(TypeFlags::HAS_TY_PARAM);
  84                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
  85             }
  86
  87             &ty::Generator(_, ref substs, _) => {
  88                 let substs = substs.as_generator();
  89                 let should_remove_further_specializable =
  90                     !self.flags.contains(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
  91                 self.add_substs(substs.parent_substs());
  92                 if should_remove_further_specializable {
  93                     self.flags -= TypeFlags::STILL_FURTHER_SPECIALIZABLE;
  94                 }
  95
  96                 self.add_ty(substs.resume_ty());
  97                 self.add_ty(substs.return_ty());
  98                 self.add_ty(substs.witness());
  99                 self.add_ty(substs.yield_ty());
 100                 self.add_ty(substs.tupled_upvars_ty());
 101             }
 102
 103             &ty::GeneratorWitness(ts) => {
 104                 let mut computation = FlagComputation::new();
 105                 computation.add_tys(ts.skip_binder());
 106                 self.add_bound_computation(computation);
 107             }
 108
 109             &ty::Closure(_, substs) => {
 110                 let substs = substs.as_closure();
 111                 let should_remove_further_specializable =
 112                     !self.flags.contains(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 113                 self.add_substs(substs.parent_substs());
 114                 if should_remove_further_specializable {
 115                     self.flags -= TypeFlags::STILL_FURTHER_SPECIALIZABLE;
 116                 }
 117
 118                 self.add_ty(substs.sig_as_fn_ptr_ty());
 119                 self.add_ty(substs.kind_ty());
 120                 self.add_ty(substs.tupled_upvars_ty());
 121             }
 122
 123             &ty::Bound(debruijn, _) => {
 124                 self.add_bound_var(debruijn);
 125             }
 126
 127             &ty::Placeholder(..) => {
 128                 self.add_flags(TypeFlags::HAS_TY_PLACEHOLDER);
 129                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 130             }
 131
 132             &ty::Infer(infer) => {
 133                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 134                 match infer {
 135                     ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_) => {}
 136
 137                     ty::TyVar(_) | ty::IntVar(_) | ty::FloatVar(_) => {
 138                         self.add_flags(TypeFlags::HAS_TY_INFER)
 139                     }
 140                 }
 141             }
 142
 143             &ty::Adt(_, substs) => {
 144                 self.add_substs(substs);
 145             }
 146
 147             &ty::Projection(data) => {
 148                 self.add_flags(TypeFlags::HAS_TY_PROJECTION);
 149                 self.add_projection_ty(data);
 150             }
 151
 152             &ty::Opaque(_, substs) => {
 153                 self.add_flags(TypeFlags::HAS_TY_OPAQUE);
 154                 self.add_substs(substs);
 155             }
 156
 157             &ty::Dynamic(ref obj, r) => {
 158                 let mut computation = FlagComputation::new();
 159                 for predicate in obj.skip_binder().iter() {
 160                     match predicate {
 161                         ty::ExistentialPredicate::Trait(tr) => computation.add_substs(tr.substs),
 162                         ty::ExistentialPredicate::Projection(p) => {
 163                             let mut proj_computation = FlagComputation::new();
 164                             proj_computation.add_existential_projection(&p);
 165                             self.add_bound_computation(proj_computation);
 166                         }
 167                         ty::ExistentialPredicate::AutoTrait(_) => {}
 168                     }
 169                 }
 170                 self.add_bound_computation(computation);
 171                 self.add_region(r);
 172             }
 173
 174             &ty::Array(tt, len) => {
 175                 self.add_ty(tt);
 176                 self.add_const(len);
 177             }
 178
 179             &ty::Slice(tt) => self.add_ty(tt),
 180
 181             &ty::RawPtr(ref m) => {
 182                 self.add_ty(m.ty);
 183             }
 184
 185             &ty::Ref(r, ty, _) => {
 186                 self.add_region(r);
 187                 self.add_ty(ty);
 188             }
 189
 190             &ty::Tuple(ref substs) => {
 191                 self.add_substs(substs);
 192             }
 193
 194             &ty::FnDef(_, substs) => {
 195                 self.add_substs(substs);
 196             }
 197
 198             &ty::FnPtr(f) => {
 199                 self.add_fn_sig(f);
 200             }
 201         }
 202     }
 203
 204     fn add_predicate_kind(&mut self, kind: &ty::PredicateKind<'_>) {
 205         match kind {
 206             ty::PredicateKind::ForAll(binder) => {
 207                 let mut computation = FlagComputation::new();
 208
 209                 computation.add_predicate_atom(binder.skip_binder());
 210
 211                 self.add_bound_computation(computation);
 212             }
 213             &ty::PredicateKind::Atom(atom) => self.add_predicate_atom(atom),
 214         }
 215     }
 216
 217     fn add_predicate_atom(&mut self, atom: ty::PredicateAtom<'_>) {
 218         match atom {
 219             ty::PredicateAtom::Trait(trait_pred, _constness) => {
 220                 self.add_substs(trait_pred.trait_ref.substs);
 221             }
 222             ty::PredicateAtom::RegionOutlives(ty::OutlivesPredicate(a, b)) => {
 223                 self.add_region(a);
 224                 self.add_region(b);
 225             }
 226             ty::PredicateAtom::TypeOutlives(ty::OutlivesPredicate(ty, region)) => {
 227                 self.add_ty(ty);
 228                 self.add_region(region);
 229             }
 230             ty::PredicateAtom::Subtype(ty::SubtypePredicate { a_is_expected: _, a, b }) => {
 231                 self.add_ty(a);
 232                 self.add_ty(b);
 233             }
 234             ty::PredicateAtom::Projection(ty::ProjectionPredicate { projection_ty, ty }) => {
 235                 self.add_projection_ty(projection_ty);
 236                 self.add_ty(ty);
 237             }
 238             ty::PredicateAtom::WellFormed(arg) => {
 239                 self.add_substs(slice::from_ref(&arg));
 240             }
 241             ty::PredicateAtom::ObjectSafe(_def_id) => {}
 242             ty::PredicateAtom::ClosureKind(_def_id, substs, _kind) => {
 243                 self.add_substs(substs);
 244             }
 245             ty::PredicateAtom::ConstEvaluatable(_def_id, substs) => {
 246                 self.add_substs(substs);
 247             }
 248             ty::PredicateAtom::ConstEquate(expected, found) => {
 249                 self.add_const(expected);
 250                 self.add_const(found);
 251             }
 252         }
 253     }
 254
 255     fn add_ty(&mut self, ty: Ty<'_>) {
 256         self.add_flags(ty.flags);
 257         self.add_exclusive_binder(ty.outer_exclusive_binder);
 258     }
 259
 260     fn add_tys(&mut self, tys: &[Ty<'_>]) {
 261         for &ty in tys {
 262             self.add_ty(ty);
 263         }
 264     }
 265
 266     fn add_fn_sig(&mut self, fn_sig: ty::PolyFnSig<'_>) {
 267         let mut computation = FlagComputation::new();
 268
 269         computation.add_tys(fn_sig.skip_binder().inputs());
 270         computation.add_ty(fn_sig.skip_binder().output());
 271
 272         self.add_bound_computation(computation);
 273     }
 274
 275     fn add_region(&mut self, r: ty::Region<'_>) {
 276         self.add_flags(r.type_flags());
 277         if let ty::ReLateBound(debruijn, _) = *r {
 278             self.add_bound_var(debruijn);
 279         }
 280     }
 281
 282     fn add_const(&mut self, c: &ty::Const<'_>) {
 283         self.add_ty(c.ty);
 284         match c.val {
 285             ty::ConstKind::Unevaluated(_, substs, _) => {
 286                 self.add_substs(substs);
 287                 self.add_flags(TypeFlags::HAS_CT_PROJECTION);
 288             }
 289             ty::ConstKind::Infer(infer) => {
 290                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 291                 match infer {
 292                     InferConst::Fresh(_) => {}
 293                     InferConst::Var(_) => self.add_flags(TypeFlags::HAS_CT_INFER),
 294                 }
 295             }
 296             ty::ConstKind::Bound(debruijn, _) => {
 297                 self.add_bound_var(debruijn);
 298             }
 299             ty::ConstKind::Param(_) => {
 300                 self.add_flags(TypeFlags::HAS_CT_PARAM);
 301                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 302             }
 303             ty::ConstKind::Placeholder(_) => {
 304                 self.add_flags(TypeFlags::HAS_CT_PLACEHOLDER);
 305                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 306             }
 307             ty::ConstKind::Value(_) => {}
 308             ty::ConstKind::Error(_) => self.add_flags(TypeFlags::HAS_ERROR),
 309         }
 310     }
 311
 312     fn add_existential_projection(&mut self, projection: &ty::ExistentialProjection<'_>) {
 313         self.add_substs(projection.substs);
 314         self.add_ty(projection.ty);
 315     }
 316
 317     fn add_projection_ty(&mut self, projection_ty: ty::ProjectionTy<'_>) {
 318         self.add_substs(projection_ty.substs);
 319     }
 320
 321     fn add_substs(&mut self, substs: &[GenericArg<'_>]) {
 322         for kind in substs {
 323             match kind.unpack() {
 324                 GenericArgKind::Type(ty) => self.add_ty(ty),
 325                 GenericArgKind::Lifetime(lt) => self.add_region(lt),
 326                 GenericArgKind::Const(ct) => self.add_const(ct),
 327             }
 328         }
 329     }
 330 }