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<'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     pub fn for_unevaluated_const(uv: ty::Unevaluated<'_>) -> TypeFlags {
  38         let mut result = FlagComputation::new();
  39         result.add_unevaluated_const(uv);
  40         result.flags
  41     }
  42
  43     fn add_flags(&mut self, flags: TypeFlags) {
  44         self.flags = self.flags | flags;
  45     }
  46
  47     /// indicates that `self` refers to something at binding level `binder`
  48     fn add_bound_var(&mut self, binder: ty::DebruijnIndex) {
  49         let exclusive_binder = binder.shifted_in(1);
  50         self.add_exclusive_binder(exclusive_binder);
  51     }
  52
  53     /// indicates that `self` refers to something *inside* binding
  54     /// level `binder` -- not bound by `binder`, but bound by the next
  55     /// binder internal to it
  56     fn add_exclusive_binder(&mut self, exclusive_binder: ty::DebruijnIndex) {
  57         self.outer_exclusive_binder = self.outer_exclusive_binder.max(exclusive_binder);
  58     }
  59
  60     /// Adds the flags/depth from a set of types that appear within the current type, but within a
  61     /// region binder.
  62     fn bound_computation<T, F>(&mut self, value: ty::Binder<'_, T>, f: F)
  63     where
  64         F: FnOnce(&mut Self, T),
  65     {
  66         let mut computation = FlagComputation::new();
  67
  68         if !value.bound_vars().is_empty() {
  69             computation.flags = computation.flags | TypeFlags::HAS_RE_LATE_BOUND;
  70         }
  71
  72         f(&mut computation, value.skip_binder());
  73
  74         self.add_flags(computation.flags);
  75
  76         // The types that contributed to `computation` occurred within
  77         // a region binder, so subtract one from the region depth
  78         // within when adding the depth to `self`.
  79         let outer_exclusive_binder = computation.outer_exclusive_binder;
  80         if outer_exclusive_binder > ty::INNERMOST {
  81             self.add_exclusive_binder(outer_exclusive_binder.shifted_out(1));
  82         } // otherwise, this binder captures nothing
  83     }
  84
  85     #[allow(rustc::usage_of_ty_tykind)]
  86     fn add_kind(&mut self, kind: &ty::TyKind<'_>) {
  87         match kind {
  88             &ty::Bool
  89             | &ty::Char
  90             | &ty::Int(_)
  91             | &ty::Float(_)
  92             | &ty::Uint(_)
  93             | &ty::Never
  94             | &ty::Str
  95             | &ty::Foreign(..) => {}
  96
  97             &ty::Error(_) => self.add_flags(TypeFlags::HAS_ERROR),
  98
  99             &ty::Param(_) => {
 100                 self.add_flags(TypeFlags::HAS_KNOWN_TY_PARAM);
 101                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 102             }
 103
 104             &ty::Generator(_, ref substs, _) => {
 105                 let substs = substs.as_generator();
 106                 let should_remove_further_specializable =
 107                     !self.flags.contains(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 108                 self.add_substs(substs.parent_substs());
 109                 if should_remove_further_specializable {
 110                     self.flags -= TypeFlags::STILL_FURTHER_SPECIALIZABLE;
 111                 }
 112
 113                 self.add_ty(substs.resume_ty());
 114                 self.add_ty(substs.return_ty());
 115                 self.add_ty(substs.witness());
 116                 self.add_ty(substs.yield_ty());
 117                 self.add_ty(substs.tupled_upvars_ty());
 118             }
 119
 120             &ty::GeneratorWitness(ts) => {
 121                 self.bound_computation(ts, |flags, ts| flags.add_tys(ts));
 122             }
 123
 124             &ty::Closure(_, substs) => {
 125                 let substs = substs.as_closure();
 126                 let should_remove_further_specializable =
 127                     !self.flags.contains(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 128                 self.add_substs(substs.parent_substs());
 129                 if should_remove_further_specializable {
 130                     self.flags -= TypeFlags::STILL_FURTHER_SPECIALIZABLE;
 131                 }
 132
 133                 self.add_ty(substs.sig_as_fn_ptr_ty());
 134                 self.add_ty(substs.kind_ty());
 135                 self.add_ty(substs.tupled_upvars_ty());
 136             }
 137
 138             &ty::Bound(debruijn, _) => {
 139                 self.add_bound_var(debruijn);
 140             }
 141
 142             &ty::Placeholder(..) => {
 143                 self.add_flags(TypeFlags::HAS_TY_PLACEHOLDER);
 144                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 145             }
 146
 147             &ty::Infer(infer) => {
 148                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 149                 match infer {
 150                     ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_) => {
 151                         self.add_flags(TypeFlags::HAS_TY_FRESH)
 152                     }
 153
 154                     ty::TyVar(_) | ty::IntVar(_) | ty::FloatVar(_) => {
 155                         self.add_flags(TypeFlags::HAS_TY_INFER)
 156                     }
 157                 }
 158             }
 159
 160             &ty::Adt(_, substs) => {
 161                 self.add_substs(substs);
 162             }
 163
 164             &ty::Projection(data) => {
 165                 self.add_flags(TypeFlags::HAS_TY_PROJECTION);
 166                 self.add_projection_ty(data);
 167             }
 168
 169             &ty::Opaque(_, substs) => {
 170                 self.add_flags(TypeFlags::HAS_TY_OPAQUE);
 171                 self.add_substs(substs);
 172             }
 173
 174             &ty::Dynamic(obj, r) => {
 175                 for predicate in obj.iter() {
 176                     self.bound_computation(predicate, |computation, predicate| match predicate {
 177                         ty::ExistentialPredicate::Trait(tr) => computation.add_substs(tr.substs),
 178                         ty::ExistentialPredicate::Projection(p) => {
 179                             computation.add_existential_projection(&p);
 180                         }
 181                         ty::ExistentialPredicate::AutoTrait(_) => {}
 182                     });
 183                 }
 184
 185                 self.add_region(r);
 186             }
 187
 188             &ty::Array(tt, len) => {
 189                 self.add_ty(tt);
 190                 self.add_const(len);
 191             }
 192
 193             &ty::Slice(tt) => self.add_ty(tt),
 194
 195             &ty::RawPtr(ref m) => {
 196                 self.add_ty(m.ty);
 197             }
 198
 199             &ty::Ref(r, ty, _) => {
 200                 self.add_region(r);
 201                 self.add_ty(ty);
 202             }
 203
 204             &ty::Tuple(ref substs) => {
 205                 self.add_substs(substs);
 206             }
 207
 208             &ty::FnDef(_, substs) => {
 209                 self.add_substs(substs);
 210             }
 211
 212             &ty::FnPtr(fn_sig) => self.bound_computation(fn_sig, |computation, fn_sig| {
 213                 computation.add_tys(fn_sig.inputs());
 214                 computation.add_ty(fn_sig.output());
 215             }),
 216         }
 217     }
 218
 219     fn add_predicate(&mut self, binder: ty::Binder<'tcx, ty::PredicateKind<'_>>) {
 220         self.bound_computation(binder, |computation, atom| computation.add_predicate_atom(atom));
 221     }
 222
 223     fn add_predicate_atom(&mut self, atom: ty::PredicateKind<'_>) {
 224         match atom {
 225             ty::PredicateKind::Trait(trait_pred) => {
 226                 self.add_substs(trait_pred.trait_ref.substs);
 227             }
 228             ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => {
 229                 self.add_region(a);
 230                 self.add_region(b);
 231             }
 232             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(ty, region)) => {
 233                 self.add_ty(ty);
 234                 self.add_region(region);
 235             }
 236             ty::PredicateKind::Subtype(ty::SubtypePredicate { a_is_expected: _, a, b }) => {
 237                 self.add_ty(a);
 238                 self.add_ty(b);
 239             }
 240             ty::PredicateKind::Coerce(ty::CoercePredicate { a, b }) => {
 241                 self.add_ty(a);
 242                 self.add_ty(b);
 243             }
 244             ty::PredicateKind::Projection(ty::ProjectionPredicate { projection_ty, ty }) => {
 245                 self.add_projection_ty(projection_ty);
 246                 self.add_ty(ty);
 247             }
 248             ty::PredicateKind::WellFormed(arg) => {
 249                 self.add_substs(slice::from_ref(&arg));
 250             }
 251             ty::PredicateKind::ObjectSafe(_def_id) => {}
 252             ty::PredicateKind::ClosureKind(_def_id, substs, _kind) => {
 253                 self.add_substs(substs);
 254             }
 255             ty::PredicateKind::ConstEvaluatable(uv) => {
 256                 self.add_unevaluated_const(uv);
 257             }
 258             ty::PredicateKind::ConstEquate(expected, found) => {
 259                 self.add_const(expected);
 260                 self.add_const(found);
 261             }
 262             ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
 263                 self.add_ty(ty);
 264             }
 265         }
 266     }
 267
 268     fn add_ty(&mut self, ty: Ty<'_>) {
 269         self.add_flags(ty.flags());
 270         self.add_exclusive_binder(ty.outer_exclusive_binder);
 271     }
 272
 273     fn add_tys(&mut self, tys: &[Ty<'_>]) {
 274         for &ty in tys {
 275             self.add_ty(ty);
 276         }
 277     }
 278
 279     fn add_region(&mut self, r: ty::Region<'_>) {
 280         self.add_flags(r.type_flags());
 281         if let ty::ReLateBound(debruijn, _) = *r {
 282             self.add_bound_var(debruijn);
 283         }
 284     }
 285
 286     fn add_const(&mut self, c: &ty::Const<'_>) {
 287         self.add_ty(c.ty);
 288         match c.val {
 289             ty::ConstKind::Unevaluated(unevaluated) => self.add_unevaluated_const(unevaluated),
 290             ty::ConstKind::Infer(infer) => {
 291                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 292                 match infer {
 293                     InferConst::Fresh(_) => self.add_flags(TypeFlags::HAS_CT_FRESH),
 294                     InferConst::Var(_) => self.add_flags(TypeFlags::HAS_CT_INFER),
 295                 }
 296             }
 297             ty::ConstKind::Bound(debruijn, _) => {
 298                 self.add_bound_var(debruijn);
 299             }
 300             ty::ConstKind::Param(_) => {
 301                 self.add_flags(TypeFlags::HAS_KNOWN_CT_PARAM);
 302                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 303             }
 304             ty::ConstKind::Placeholder(_) => {
 305                 self.add_flags(TypeFlags::HAS_CT_PLACEHOLDER);
 306                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 307             }
 308             ty::ConstKind::Value(_) => {}
 309             ty::ConstKind::Error(_) => self.add_flags(TypeFlags::HAS_ERROR),
 310         }
 311     }
 312
 313     fn add_unevaluated_const<P>(&mut self, ct: ty::Unevaluated<'tcx, P>) {
 314         // The generic arguments of unevaluated consts are a bit special,
 315         // see the `rustc-dev-guide` for more information.
 316         //
 317         // FIXME(@lcnr): Actually add a link here.
 318         if let Some(substs) = ct.substs_ {
 319             // If they are available, we treat them as ordinary generic arguments.
 320             self.add_substs(substs);
 321         } else {
 322             // Otherwise, we add `HAS_UNKNOWN_DEFAULT_CONST_SUBSTS` to signify
 323             // that our const may potentially refer to generic parameters.
 324             //
 325             // Note that depending on which generic parameters are actually
 326             // used in this constant, we may not actually refer to any generic
 327             // parameters at all.
 328             self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
 329             self.add_flags(TypeFlags::HAS_UNKNOWN_DEFAULT_CONST_SUBSTS);
 330         }
 331         self.add_flags(TypeFlags::HAS_CT_PROJECTION);
 332     }
 333
 334     fn add_existential_projection(&mut self, projection: &ty::ExistentialProjection<'_>) {
 335         self.add_substs(projection.substs);
 336         self.add_ty(projection.ty);
 337     }
 338
 339     fn add_projection_ty(&mut self, projection_ty: ty::ProjectionTy<'_>) {
 340         self.add_substs(projection_ty.substs);
 341     }
 342
 343     fn add_substs(&mut self, substs: &[GenericArg<'_>]) {
 344         for kind in substs {
 345             match kind.unpack() {
 346                 GenericArgKind::Type(ty) => self.add_ty(ty),
 347                 GenericArgKind::Lifetime(lt) => self.add_region(lt),
 348                 GenericArgKind::Const(ct) => self.add_const(ct),
 349             }
 350         }
 351     }
 352 }