compiler/rustc_middle/src/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(binder: ty::Binder<ty::PredicateKind<'_>>) -> FlagComputation {
  26         let mut result = FlagComputation::new();
  27         result.add_predicate(binder);
  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 bound_computation<T, F>(&mut self, value: ty::Binder<T>, f: F)
  57     where
  58         F: FnOnce(&mut Self, T),
  59     {
  60         let mut computation = FlagComputation::new();
  61
  62         f(&mut computation, value.skip_binder());
  63
  64         self.add_flags(computation.flags);
  65
  66         // The types that contributed to `computation` occurred within
  67         // a region binder, so subtract one from the region depth
  68         // within when adding the depth to `self`.
  69         let outer_exclusive_binder = computation.outer_exclusive_binder;
  70         if outer_exclusive_binder > ty::INNERMOST {
  71             self.add_exclusive_binder(outer_exclusive_binder.shifted_out(1));
  72         } // otherwise, this binder captures nothing
  73     }
  74
  75     #[allow(rustc::usage_of_ty_tykind)]
  76     fn add_kind(&mut self, kind: &ty::TyKind<'_>) {
  77         match kind {
  78             &ty::Bool
  79             | &ty::Char
  80             | &ty::Int(_)
  81             | &ty::Float(_)
  82             | &ty::Uint(_)
  83             | &ty::Never
  84             | &ty::Str
  85             | &ty::Foreign(..) => {}
  86
  87             &ty::Error(_) => self.add_flags(TypeFlags::HAS_ERROR),
  88
  89             &ty::Param(_) => {
  90                 self.add_flags(TypeFlags::HAS_TY_PARAM);
  91                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
  92             }
  93
  94             &ty::Generator(_, ref substs, _) => {
  95                 let substs = substs.as_generator();
  96                 let should_remove_further_specializable =
  97                     !self.flags.contains(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
  98                 self.add_substs(substs.parent_substs());
  99                 if should_remove_further_specializable {
 100                     self.flags -= TypeFlags::STILL_FURTHER_SPECIALIZABLE;
 101                 }
 102
 103                 self.add_ty(substs.resume_ty());
 104                 self.add_ty(substs.return_ty());
 105                 self.add_ty(substs.witness());
 106                 self.add_ty(substs.yield_ty());
 107                 self.add_ty(substs.tupled_upvars_ty());
 108             }
 109
 110             &ty::GeneratorWitness(ts) => {
 111                 self.bound_computation(ts, |flags, ts| flags.add_tys(ts));
 112             }
 113
 114             &ty::Closure(_, substs) => {
 115                 let substs = substs.as_closure();
 116                 let should_remove_further_specializable =
 117                     !self.flags.contains(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 118                 self.add_substs(substs.parent_substs());
 119                 if should_remove_further_specializable {
 120                     self.flags -= TypeFlags::STILL_FURTHER_SPECIALIZABLE;
 121                 }
 122
 123                 self.add_ty(substs.sig_as_fn_ptr_ty());
 124                 self.add_ty(substs.kind_ty());
 125                 self.add_ty(substs.tupled_upvars_ty());
 126             }
 127
 128             &ty::Bound(debruijn, _) => {
 129                 self.add_bound_var(debruijn);
 130             }
 131
 132             &ty::Placeholder(..) => {
 133                 self.add_flags(TypeFlags::HAS_TY_PLACEHOLDER);
 134                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 135             }
 136
 137             &ty::Infer(infer) => {
 138                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 139                 match infer {
 140                     ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_) => {}
 141
 142                     ty::TyVar(_) | ty::IntVar(_) | ty::FloatVar(_) => {
 143                         self.add_flags(TypeFlags::HAS_TY_INFER)
 144                     }
 145                 }
 146             }
 147
 148             &ty::Adt(_, substs) => {
 149                 self.add_substs(substs);
 150             }
 151
 152             &ty::Projection(data) => {
 153                 self.add_flags(TypeFlags::HAS_TY_PROJECTION);
 154                 self.add_projection_ty(data);
 155             }
 156
 157             &ty::Opaque(_, substs) => {
 158                 self.add_flags(TypeFlags::HAS_TY_OPAQUE);
 159                 self.add_substs(substs);
 160             }
 161
 162             &ty::Dynamic(obj, r) => {
 163                 for predicate in obj.iter() {
 164                     self.bound_computation(predicate, |computation, predicate| match predicate {
 165                         ty::ExistentialPredicate::Trait(tr) => computation.add_substs(tr.substs),
 166                         ty::ExistentialPredicate::Projection(p) => {
 167                             computation.add_existential_projection(&p);
 168                         }
 169                         ty::ExistentialPredicate::AutoTrait(_) => {}
 170                     });
 171                 }
 172
 173                 self.add_region(r);
 174             }
 175
 176             &ty::Array(tt, len) => {
 177                 self.add_ty(tt);
 178                 self.add_const(len);
 179             }
 180
 181             &ty::Slice(tt) => self.add_ty(tt),
 182
 183             &ty::RawPtr(ref m) => {
 184                 self.add_ty(m.ty);
 185             }
 186
 187             &ty::Ref(r, ty, _) => {
 188                 self.add_region(r);
 189                 self.add_ty(ty);
 190             }
 191
 192             &ty::Tuple(ref substs) => {
 193                 self.add_substs(substs);
 194             }
 195
 196             &ty::FnDef(_, substs) => {
 197                 self.add_substs(substs);
 198             }
 199
 200             &ty::FnPtr(fn_sig) => self.bound_computation(fn_sig, |computation, fn_sig| {
 201                 computation.add_tys(fn_sig.inputs());
 202                 computation.add_ty(fn_sig.output());
 203             }),
 204         }
 205     }
 206
 207     fn add_predicate(&mut self, binder: ty::Binder<ty::PredicateKind<'_>>) {
 208         self.bound_computation(binder, |computation, atom| computation.add_predicate_atom(atom));
 209     }
 210
 211     fn add_predicate_atom(&mut self, atom: ty::PredicateKind<'_>) {
 212         match atom {
 213             ty::PredicateKind::Trait(trait_pred, _constness) => {
 214                 self.add_substs(trait_pred.trait_ref.substs);
 215             }
 216             ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => {
 217                 self.add_region(a);
 218                 self.add_region(b);
 219             }
 220             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(ty, region)) => {
 221                 self.add_ty(ty);
 222                 self.add_region(region);
 223             }
 224             ty::PredicateKind::Subtype(ty::SubtypePredicate { a_is_expected: _, a, b }) => {
 225                 self.add_ty(a);
 226                 self.add_ty(b);
 227             }
 228             ty::PredicateKind::Projection(ty::ProjectionPredicate { projection_ty, ty }) => {
 229                 self.add_projection_ty(projection_ty);
 230                 self.add_ty(ty);
 231             }
 232             ty::PredicateKind::WellFormed(arg) => {
 233                 self.add_substs(slice::from_ref(&arg));
 234             }
 235             ty::PredicateKind::ObjectSafe(_def_id) => {}
 236             ty::PredicateKind::ClosureKind(_def_id, substs, _kind) => {
 237                 self.add_substs(substs);
 238             }
 239             ty::PredicateKind::ConstEvaluatable(_def_id, substs) => {
 240                 self.add_substs(substs);
 241             }
 242             ty::PredicateKind::ConstEquate(expected, found) => {
 243                 self.add_const(expected);
 244                 self.add_const(found);
 245             }
 246             ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
 247                 self.add_ty(ty);
 248             }
 249         }
 250     }
 251
 252     fn add_ty(&mut self, ty: Ty<'_>) {
 253         self.add_flags(ty.flags());
 254         self.add_exclusive_binder(ty.outer_exclusive_binder);
 255     }
 256
 257     fn add_tys(&mut self, tys: &[Ty<'_>]) {
 258         for &ty in tys {
 259             self.add_ty(ty);
 260         }
 261     }
 262
 263     fn add_region(&mut self, r: ty::Region<'_>) {
 264         self.add_flags(r.type_flags());
 265         if let ty::ReLateBound(debruijn, _) = *r {
 266             self.add_bound_var(debruijn);
 267         }
 268     }
 269
 270     fn add_const(&mut self, c: &ty::Const<'_>) {
 271         self.add_ty(c.ty);
 272         match c.val {
 273             ty::ConstKind::Unevaluated(unevaluated) => self.add_unevaluated_const(unevaluated),
 274             ty::ConstKind::Infer(infer) => {
 275                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 276                 match infer {
 277                     InferConst::Fresh(_) => {}
 278                     InferConst::Var(_) => self.add_flags(TypeFlags::HAS_CT_INFER),
 279                 }
 280             }
 281             ty::ConstKind::Bound(debruijn, _) => {
 282                 self.add_bound_var(debruijn);
 283             }
 284             ty::ConstKind::Param(_) => {
 285                 self.add_flags(TypeFlags::HAS_CT_PARAM);
 286                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 287             }
 288             ty::ConstKind::Placeholder(_) => {
 289                 self.add_flags(TypeFlags::HAS_CT_PLACEHOLDER);
 290                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 291             }
 292             ty::ConstKind::Value(_) => {}
 293             ty::ConstKind::Error(_) => self.add_flags(TypeFlags::HAS_ERROR),
 294         }
 295     }
 296
 297     fn add_unevaluated_const(&mut self, ct: ty::Unevaluated<'tcx>) {
 298         self.add_substs(ct.substs);
 299         self.add_flags(TypeFlags::HAS_CT_PROJECTION);
 300     }
 301
 302     fn add_existential_projection(&mut self, projection: &ty::ExistentialProjection<'_>) {
 303         self.add_substs(projection.substs);
 304         self.add_ty(projection.ty);
 305     }
 306
 307     fn add_projection_ty(&mut self, projection_ty: ty::ProjectionTy<'_>) {
 308         self.add_substs(projection_ty.substs);
 309     }
 310
 311     fn add_substs(&mut self, substs: &[GenericArg<'_>]) {
 312         for kind in substs {
 313             match kind.unpack() {
 314                 GenericArgKind::Type(ty) => self.add_ty(ty),
 315                 GenericArgKind::Lifetime(lt) => self.add_region(lt),
 316                 GenericArgKind::Const(ct) => self.add_const(ct),
 317             }
 318         }
 319     }
 320 }