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                 self.add_substs(substs);
  89             }
  90
  91             &ty::GeneratorWitness(ts) => {
  92                 let mut computation = FlagComputation::new();
  93                 computation.add_tys(ts.skip_binder());
  94                 self.add_bound_computation(computation);
  95             }
  96
  97             &ty::Closure(_, substs) => {
  98                 self.add_substs(substs);
  99             }
 100
 101             &ty::Bound(debruijn, _) => {
 102                 self.add_bound_var(debruijn);
 103             }
 104
 105             &ty::Placeholder(..) => {
 106                 self.add_flags(TypeFlags::HAS_TY_PLACEHOLDER);
 107                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 108             }
 109
 110             &ty::Infer(infer) => {
 111                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 112                 match infer {
 113                     ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_) => {}
 114
 115                     ty::TyVar(_) | ty::IntVar(_) | ty::FloatVar(_) => {
 116                         self.add_flags(TypeFlags::HAS_TY_INFER)
 117                     }
 118                 }
 119             }
 120
 121             &ty::Adt(_, substs) => {
 122                 self.add_substs(substs);
 123             }
 124
 125             &ty::Projection(data) => {
 126                 self.add_flags(TypeFlags::HAS_TY_PROJECTION);
 127                 self.add_projection_ty(data);
 128             }
 129
 130             &ty::Opaque(_, substs) => {
 131                 self.add_flags(TypeFlags::HAS_TY_OPAQUE);
 132                 self.add_substs(substs);
 133             }
 134
 135             &ty::Dynamic(ref obj, r) => {
 136                 let mut computation = FlagComputation::new();
 137                 for predicate in obj.skip_binder().iter() {
 138                     match predicate {
 139                         ty::ExistentialPredicate::Trait(tr) => computation.add_substs(tr.substs),
 140                         ty::ExistentialPredicate::Projection(p) => {
 141                             let mut proj_computation = FlagComputation::new();
 142                             proj_computation.add_existential_projection(&p);
 143                             self.add_bound_computation(proj_computation);
 144                         }
 145                         ty::ExistentialPredicate::AutoTrait(_) => {}
 146                     }
 147                 }
 148                 self.add_bound_computation(computation);
 149                 self.add_region(r);
 150             }
 151
 152             &ty::Array(tt, len) => {
 153                 self.add_ty(tt);
 154                 self.add_const(len);
 155             }
 156
 157             &ty::Slice(tt) => self.add_ty(tt),
 158
 159             &ty::RawPtr(ref m) => {
 160                 self.add_ty(m.ty);
 161             }
 162
 163             &ty::Ref(r, ty, _) => {
 164                 self.add_region(r);
 165                 self.add_ty(ty);
 166             }
 167
 168             &ty::Tuple(ref substs) => {
 169                 self.add_substs(substs);
 170             }
 171
 172             &ty::FnDef(_, substs) => {
 173                 self.add_substs(substs);
 174             }
 175
 176             &ty::FnPtr(f) => {
 177                 self.add_fn_sig(f);
 178             }
 179         }
 180     }
 181
 182     fn add_predicate_kind(&mut self, kind: &ty::PredicateKind<'_>) {
 183         match kind {
 184             ty::PredicateKind::Trait(trait_pred, _constness) => {
 185                 let mut computation = FlagComputation::new();
 186                 computation.add_substs(trait_pred.skip_binder().trait_ref.substs);
 187
 188                 self.add_bound_computation(computation);
 189             }
 190             ty::PredicateKind::RegionOutlives(poly_outlives) => {
 191                 let mut computation = FlagComputation::new();
 192                 let ty::OutlivesPredicate(a, b) = poly_outlives.skip_binder();
 193                 computation.add_region(a);
 194                 computation.add_region(b);
 195
 196                 self.add_bound_computation(computation);
 197             }
 198             ty::PredicateKind::TypeOutlives(poly_outlives) => {
 199                 let mut computation = FlagComputation::new();
 200                 let ty::OutlivesPredicate(ty, region) = poly_outlives.skip_binder();
 201                 computation.add_ty(ty);
 202                 computation.add_region(region);
 203
 204                 self.add_bound_computation(computation);
 205             }
 206             ty::PredicateKind::Subtype(poly_subtype) => {
 207                 let mut computation = FlagComputation::new();
 208                 let ty::SubtypePredicate { a_is_expected: _, a, b } = poly_subtype.skip_binder();
 209                 computation.add_ty(a);
 210                 computation.add_ty(b);
 211
 212                 self.add_bound_computation(computation);
 213             }
 214             &ty::PredicateKind::Projection(projection) => {
 215                 let mut computation = FlagComputation::new();
 216                 let ty::ProjectionPredicate { projection_ty, ty } = projection.skip_binder();
 217                 computation.add_projection_ty(projection_ty);
 218                 computation.add_ty(ty);
 219
 220                 self.add_bound_computation(computation);
 221             }
 222             ty::PredicateKind::WellFormed(arg) => {
 223                 self.add_substs(slice::from_ref(arg));
 224             }
 225             ty::PredicateKind::ObjectSafe(_def_id) => {}
 226             ty::PredicateKind::ClosureKind(_def_id, substs, _kind) => {
 227                 self.add_substs(substs);
 228             }
 229             ty::PredicateKind::ConstEvaluatable(_def_id, substs) => {
 230                 self.add_substs(substs);
 231             }
 232             ty::PredicateKind::ConstEquate(expected, found) => {
 233                 self.add_const(expected);
 234                 self.add_const(found);
 235             }
 236         }
 237     }
 238
 239     fn add_ty(&mut self, ty: Ty<'_>) {
 240         self.add_flags(ty.flags);
 241         self.add_exclusive_binder(ty.outer_exclusive_binder);
 242     }
 243
 244     fn add_tys(&mut self, tys: &[Ty<'_>]) {
 245         for &ty in tys {
 246             self.add_ty(ty);
 247         }
 248     }
 249
 250     fn add_fn_sig(&mut self, fn_sig: ty::PolyFnSig<'_>) {
 251         let mut computation = FlagComputation::new();
 252
 253         computation.add_tys(fn_sig.skip_binder().inputs());
 254         computation.add_ty(fn_sig.skip_binder().output());
 255
 256         self.add_bound_computation(computation);
 257     }
 258
 259     fn add_region(&mut self, r: ty::Region<'_>) {
 260         self.add_flags(r.type_flags());
 261         if let ty::ReLateBound(debruijn, _) = *r {
 262             self.add_bound_var(debruijn);
 263         }
 264     }
 265
 266     fn add_const(&mut self, c: &ty::Const<'_>) {
 267         self.add_ty(c.ty);
 268         match c.val {
 269             ty::ConstKind::Unevaluated(_, substs, _) => {
 270                 self.add_substs(substs);
 271                 self.add_flags(TypeFlags::HAS_CT_PROJECTION);
 272             }
 273             ty::ConstKind::Infer(infer) => {
 274                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 275                 match infer {
 276                     InferConst::Fresh(_) => {}
 277                     InferConst::Var(_) => self.add_flags(TypeFlags::HAS_CT_INFER),
 278                 }
 279             }
 280             ty::ConstKind::Bound(debruijn, _) => {
 281                 self.add_bound_var(debruijn);
 282             }
 283             ty::ConstKind::Param(_) => {
 284                 self.add_flags(TypeFlags::HAS_CT_PARAM);
 285                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 286             }
 287             ty::ConstKind::Placeholder(_) => {
 288                 self.add_flags(TypeFlags::HAS_CT_PLACEHOLDER);
 289                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 290             }
 291             ty::ConstKind::Value(_) => {}
 292             ty::ConstKind::Error(_) => self.add_flags(TypeFlags::HAS_ERROR),
 293         }
 294     }
 295
 296     fn add_existential_projection(&mut self, projection: &ty::ExistentialProjection<'_>) {
 297         self.add_substs(projection.substs);
 298         self.add_ty(projection.ty);
 299     }
 300
 301     fn add_projection_ty(&mut self, projection_ty: ty::ProjectionTy<'_>) {
 302         self.add_substs(projection_ty.substs);
 303     }
 304
 305     fn add_substs(&mut self, substs: &[GenericArg<'_>]) {
 306         for kind in substs {
 307             match kind.unpack() {
 308                 GenericArgKind::Type(ty) => self.add_ty(ty),
 309                 GenericArgKind::Lifetime(lt) => self.add_region(lt),
 310                 GenericArgKind::Const(ct) => self.add_const(ct),
 311             }
 312         }
 313     }
 314 }