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 `Ty::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<'tcx>(binder: ty::Binder<'tcx, 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         if !value.bound_vars().is_empty() {
  63             computation.flags = computation.flags | TypeFlags::HAS_RE_LATE_BOUND;
  64         }
  65
  66         f(&mut computation, value.skip_binder());
  67
  68         self.add_flags(computation.flags);
  69
  70         // The types that contributed to `computation` occurred within
  71         // a region binder, so subtract one from the region depth
  72         // within when adding the depth to `self`.
  73         let outer_exclusive_binder = computation.outer_exclusive_binder;
  74         if outer_exclusive_binder > ty::INNERMOST {
  75             self.add_exclusive_binder(outer_exclusive_binder.shifted_out(1));
  76         } // otherwise, this binder captures nothing
  77     }
  78
  79     #[allow(rustc::usage_of_ty_tykind)]
  80     fn add_kind(&mut self, kind: &ty::TyKind<'_>) {
  81         match kind {
  82             &ty::Bool
  83             | &ty::Char
  84             | &ty::Int(_)
  85             | &ty::Float(_)
  86             | &ty::Uint(_)
  87             | &ty::Never
  88             | &ty::Str
  89             | &ty::Foreign(..) => {}
  90
  91             &ty::Error(_) => self.add_flags(TypeFlags::HAS_ERROR),
  92
  93             &ty::Param(_) => {
  94                 self.add_flags(TypeFlags::HAS_TY_PARAM);
  95                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
  96             }
  97
  98             &ty::Generator(_, ref substs, _) => {
  99                 let substs = substs.as_generator();
 100                 let should_remove_further_specializable =
 101                     !self.flags.contains(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 102                 self.add_substs(substs.parent_substs());
 103                 if should_remove_further_specializable {
 104                     self.flags -= TypeFlags::STILL_FURTHER_SPECIALIZABLE;
 105                 }
 106
 107                 self.add_ty(substs.resume_ty());
 108                 self.add_ty(substs.return_ty());
 109                 self.add_ty(substs.witness());
 110                 self.add_ty(substs.yield_ty());
 111                 self.add_ty(substs.tupled_upvars_ty());
 112             }
 113
 114             &ty::GeneratorWitness(ts) => {
 115                 self.bound_computation(ts, |flags, ts| flags.add_tys(ts));
 116             }
 117
 118             &ty::Closure(_, substs) => {
 119                 let substs = substs.as_closure();
 120                 let should_remove_further_specializable =
 121                     !self.flags.contains(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 122                 self.add_substs(substs.parent_substs());
 123                 if should_remove_further_specializable {
 124                     self.flags -= TypeFlags::STILL_FURTHER_SPECIALIZABLE;
 125                 }
 126
 127                 self.add_ty(substs.sig_as_fn_ptr_ty());
 128                 self.add_ty(substs.kind_ty());
 129                 self.add_ty(substs.tupled_upvars_ty());
 130             }
 131
 132             &ty::Bound(debruijn, _) => {
 133                 self.add_bound_var(debruijn);
 134             }
 135
 136             &ty::Placeholder(..) => {
 137                 self.add_flags(TypeFlags::HAS_TY_PLACEHOLDER);
 138                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 139             }
 140
 141             &ty::Infer(infer) => {
 142                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 143                 match infer {
 144                     ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_) => {
 145                         self.add_flags(TypeFlags::HAS_TY_FRESH)
 146                     }
 147
 148                     ty::TyVar(_) | ty::IntVar(_) | ty::FloatVar(_) => {
 149                         self.add_flags(TypeFlags::HAS_TY_INFER)
 150                     }
 151                 }
 152             }
 153
 154             &ty::Adt(_, substs) => {
 155                 self.add_substs(substs);
 156             }
 157
 158             &ty::Projection(data) => {
 159                 self.add_flags(TypeFlags::HAS_TY_PROJECTION);
 160                 self.add_projection_ty(data);
 161             }
 162
 163             &ty::Opaque(_, substs) => {
 164                 self.add_flags(TypeFlags::HAS_TY_OPAQUE);
 165                 self.add_substs(substs);
 166             }
 167
 168             &ty::Dynamic(obj, r, _) => {
 169                 for predicate in obj.iter() {
 170                     self.bound_computation(predicate, |computation, predicate| match predicate {
 171                         ty::ExistentialPredicate::Trait(tr) => computation.add_substs(tr.substs),
 172                         ty::ExistentialPredicate::Projection(p) => {
 173                             computation.add_existential_projection(&p);
 174                         }
 175                         ty::ExistentialPredicate::AutoTrait(_) => {}
 176                     });
 177                 }
 178
 179                 self.add_region(r);
 180             }
 181
 182             &ty::Array(tt, len) => {
 183                 self.add_ty(tt);
 184                 self.add_const(len);
 185             }
 186
 187             &ty::Slice(tt) => self.add_ty(tt),
 188
 189             &ty::RawPtr(ref m) => {
 190                 self.add_ty(m.ty);
 191             }
 192
 193             &ty::Ref(r, ty, _) => {
 194                 self.add_region(r);
 195                 self.add_ty(ty);
 196             }
 197
 198             &ty::Tuple(types) => {
 199                 self.add_tys(types);
 200             }
 201
 202             &ty::FnDef(_, substs) => {
 203                 self.add_substs(substs);
 204             }
 205
 206             &ty::FnPtr(fn_sig) => self.bound_computation(fn_sig, |computation, fn_sig| {
 207                 computation.add_tys(fn_sig.inputs());
 208                 computation.add_ty(fn_sig.output());
 209             }),
 210         }
 211     }
 212
 213     fn add_predicate(&mut self, binder: ty::Binder<'_, ty::PredicateKind<'_>>) {
 214         self.bound_computation(binder, |computation, atom| computation.add_predicate_atom(atom));
 215     }
 216
 217     fn add_predicate_atom(&mut self, atom: ty::PredicateKind<'_>) {
 218         match atom {
 219             ty::PredicateKind::Trait(trait_pred) => {
 220                 self.add_substs(trait_pred.trait_ref.substs);
 221             }
 222             ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => {
 223                 self.add_region(a);
 224                 self.add_region(b);
 225             }
 226             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(ty, region)) => {
 227                 self.add_ty(ty);
 228                 self.add_region(region);
 229             }
 230             ty::PredicateKind::Subtype(ty::SubtypePredicate { a_is_expected: _, a, b }) => {
 231                 self.add_ty(a);
 232                 self.add_ty(b);
 233             }
 234             ty::PredicateKind::Coerce(ty::CoercePredicate { a, b }) => {
 235                 self.add_ty(a);
 236                 self.add_ty(b);
 237             }
 238             ty::PredicateKind::Projection(ty::ProjectionPredicate { projection_ty, term }) => {
 239                 self.add_projection_ty(projection_ty);
 240                 match term.unpack() {
 241                     ty::TermKind::Ty(ty) => self.add_ty(ty),
 242                     ty::TermKind::Const(c) => self.add_const(c),
 243                 }
 244             }
 245             ty::PredicateKind::WellFormed(arg) => {
 246                 self.add_substs(slice::from_ref(&arg));
 247             }
 248             ty::PredicateKind::ObjectSafe(_def_id) => {}
 249             ty::PredicateKind::ClosureKind(_def_id, substs, _kind) => {
 250                 self.add_substs(substs);
 251             }
 252             ty::PredicateKind::ConstEvaluatable(uv) => {
 253                 self.add_const(uv);
 254             }
 255             ty::PredicateKind::ConstEquate(expected, found) => {
 256                 self.add_const(expected);
 257                 self.add_const(found);
 258             }
 259             ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
 260                 self.add_ty(ty);
 261             }
 262             ty::PredicateKind::Ambiguous => {}
 263         }
 264     }
 265
 266     fn add_ty(&mut self, ty: Ty<'_>) {
 267         self.add_flags(ty.flags());
 268         self.add_exclusive_binder(ty.outer_exclusive_binder());
 269     }
 270
 271     fn add_tys(&mut self, tys: &[Ty<'_>]) {
 272         for &ty in tys {
 273             self.add_ty(ty);
 274         }
 275     }
 276
 277     fn add_region(&mut self, r: ty::Region<'_>) {
 278         self.add_flags(r.type_flags());
 279         if let ty::ReLateBound(debruijn, _) = *r {
 280             self.add_bound_var(debruijn);
 281         }
 282     }
 283
 284     fn add_const(&mut self, c: ty::Const<'_>) {
 285         self.add_ty(c.ty());
 286         match c.kind() {
 287             ty::ConstKind::Unevaluated(uv) => {
 288                 self.add_substs(uv.substs);
 289                 self.add_flags(TypeFlags::HAS_CT_PROJECTION);
 290             }
 291             ty::ConstKind::Infer(infer) => {
 292                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 293                 match infer {
 294                     InferConst::Fresh(_) => self.add_flags(TypeFlags::HAS_CT_FRESH),
 295                     InferConst::Var(_) => self.add_flags(TypeFlags::HAS_CT_INFER),
 296                 }
 297             }
 298             ty::ConstKind::Bound(debruijn, _) => {
 299                 self.add_bound_var(debruijn);
 300             }
 301             ty::ConstKind::Param(_) => {
 302                 self.add_flags(TypeFlags::HAS_CT_PARAM);
 303                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 304             }
 305             ty::ConstKind::Placeholder(_) => {
 306                 self.add_flags(TypeFlags::HAS_CT_PLACEHOLDER);
 307                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 308             }
 309             ty::ConstKind::Value(_) => {}
 310             ty::ConstKind::Error(_) => self.add_flags(TypeFlags::HAS_ERROR),
 311         }
 312     }
 313
 314     fn add_existential_projection(&mut self, projection: &ty::ExistentialProjection<'_>) {
 315         self.add_substs(projection.substs);
 316         match projection.term.unpack() {
 317             ty::TermKind::Ty(ty) => self.add_ty(ty),
 318             ty::TermKind::Const(ct) => self.add_const(ct),
 319         }
 320     }
 321
 322     fn add_projection_ty(&mut self, projection_ty: ty::ProjectionTy<'_>) {
 323         self.add_substs(projection_ty.substs);
 324     }
 325
 326     fn add_substs(&mut self, substs: &[GenericArg<'_>]) {
 327         for kind in substs {
 328             match kind.unpack() {
 329                 GenericArgKind::Type(ty) => self.add_ty(ty),
 330                 GenericArgKind::Lifetime(lt) => self.add_region(lt),
 331                 GenericArgKind::Const(ct) => self.add_const(ct),
 332             }
 333         }
 334     }
 335 }