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::Trait(trait_pred, _constness) => {
 207                 let mut computation = FlagComputation::new();
 208                 computation.add_substs(trait_pred.skip_binder().trait_ref.substs);
 209
 210                 self.add_bound_computation(computation);
 211             }
 212             ty::PredicateKind::RegionOutlives(poly_outlives) => {
 213                 let mut computation = FlagComputation::new();
 214                 let ty::OutlivesPredicate(a, b) = poly_outlives.skip_binder();
 215                 computation.add_region(a);
 216                 computation.add_region(b);
 217
 218                 self.add_bound_computation(computation);
 219             }
 220             ty::PredicateKind::TypeOutlives(poly_outlives) => {
 221                 let mut computation = FlagComputation::new();
 222                 let ty::OutlivesPredicate(ty, region) = poly_outlives.skip_binder();
 223                 computation.add_ty(ty);
 224                 computation.add_region(region);
 225
 226                 self.add_bound_computation(computation);
 227             }
 228             ty::PredicateKind::Subtype(poly_subtype) => {
 229                 let mut computation = FlagComputation::new();
 230                 let ty::SubtypePredicate { a_is_expected: _, a, b } = poly_subtype.skip_binder();
 231                 computation.add_ty(a);
 232                 computation.add_ty(b);
 233
 234                 self.add_bound_computation(computation);
 235             }
 236             &ty::PredicateKind::Projection(projection) => {
 237                 let mut computation = FlagComputation::new();
 238                 let ty::ProjectionPredicate { projection_ty, ty } = projection.skip_binder();
 239                 computation.add_projection_ty(projection_ty);
 240                 computation.add_ty(ty);
 241
 242                 self.add_bound_computation(computation);
 243             }
 244             ty::PredicateKind::WellFormed(arg) => {
 245                 self.add_substs(slice::from_ref(arg));
 246             }
 247             ty::PredicateKind::ObjectSafe(_def_id) => {}
 248             ty::PredicateKind::ClosureKind(_def_id, substs, _kind) => {
 249                 self.add_substs(substs);
 250             }
 251             ty::PredicateKind::ConstEvaluatable(_def_id, substs) => {
 252                 self.add_substs(substs);
 253             }
 254             ty::PredicateKind::ConstEquate(expected, found) => {
 255                 self.add_const(expected);
 256                 self.add_const(found);
 257             }
 258         }
 259     }
 260
 261     fn add_ty(&mut self, ty: Ty<'_>) {
 262         self.add_flags(ty.flags);
 263         self.add_exclusive_binder(ty.outer_exclusive_binder);
 264     }
 265
 266     fn add_tys(&mut self, tys: &[Ty<'_>]) {
 267         for &ty in tys {
 268             self.add_ty(ty);
 269         }
 270     }
 271
 272     fn add_fn_sig(&mut self, fn_sig: ty::PolyFnSig<'_>) {
 273         let mut computation = FlagComputation::new();
 274
 275         computation.add_tys(fn_sig.skip_binder().inputs());
 276         computation.add_ty(fn_sig.skip_binder().output());
 277
 278         self.add_bound_computation(computation);
 279     }
 280
 281     fn add_region(&mut self, r: ty::Region<'_>) {
 282         self.add_flags(r.type_flags());
 283         if let ty::ReLateBound(debruijn, _) = *r {
 284             self.add_bound_var(debruijn);
 285         }
 286     }
 287
 288     fn add_const(&mut self, c: &ty::Const<'_>) {
 289         self.add_ty(c.ty);
 290         match c.val {
 291             ty::ConstKind::Unevaluated(_, substs, _) => {
 292                 self.add_substs(substs);
 293                 self.add_flags(TypeFlags::HAS_CT_PROJECTION);
 294             }
 295             ty::ConstKind::Infer(infer) => {
 296                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 297                 match infer {
 298                     InferConst::Fresh(_) => {}
 299                     InferConst::Var(_) => self.add_flags(TypeFlags::HAS_CT_INFER),
 300                 }
 301             }
 302             ty::ConstKind::Bound(debruijn, _) => {
 303                 self.add_bound_var(debruijn);
 304             }
 305             ty::ConstKind::Param(_) => {
 306                 self.add_flags(TypeFlags::HAS_CT_PARAM);
 307                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 308             }
 309             ty::ConstKind::Placeholder(_) => {
 310                 self.add_flags(TypeFlags::HAS_CT_PLACEHOLDER);
 311                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 312             }
 313             ty::ConstKind::Value(_) => {}
 314             ty::ConstKind::Error(_) => self.add_flags(TypeFlags::HAS_ERROR),
 315         }
 316     }
 317
 318     fn add_existential_projection(&mut self, projection: &ty::ExistentialProjection<'_>) {
 319         self.add_substs(projection.substs);
 320         self.add_ty(projection.ty);
 321     }
 322
 323     fn add_projection_ty(&mut self, projection_ty: ty::ProjectionTy<'_>) {
 324         self.add_substs(projection_ty.substs);
 325     }
 326
 327     fn add_substs(&mut self, substs: &[GenericArg<'_>]) {
 328         for kind in substs {
 329             match kind.unpack() {
 330                 GenericArgKind::Type(ty) => self.add_ty(ty),
 331                 GenericArgKind::Lifetime(lt) => self.add_region(lt),
 332                 GenericArgKind::Const(ct) => self.add_const(ct),
 333             }
 334         }
 335     }
 336 }