compiler/rustc_middle/src/ty/generics.rs

   1 use crate::middle::resolve_lifetime::ObjectLifetimeDefault;
   2 use crate::ty;
   3 use crate::ty::subst::{Subst, SubstsRef};
   4 use rustc_ast as ast;
   5 use rustc_data_structures::fx::FxHashMap;
   6 use rustc_hir as hir;
   7 use rustc_hir::def_id::DefId;
   8 use rustc_span::symbol::Symbol;
   9 use rustc_span::Span;
  10
  11 use super::{EarlyBoundRegion, InstantiatedPredicates, ParamConst, ParamTy, Predicate, TyCtxt};
  12
  13 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
  14 pub enum GenericParamDefKind {
  15     Lifetime,
  16     Type {
  17         has_default: bool,
  18         object_lifetime_default: ObjectLifetimeDefault,
  19         synthetic: Option<hir::SyntheticTyParamKind>,
  20     },
  21     Const,
  22 }
  23
  24 impl GenericParamDefKind {
  25     pub fn descr(&self) -> &'static str {
  26         match self {
  27             GenericParamDefKind::Lifetime => "lifetime",
  28             GenericParamDefKind::Type { .. } => "type",
  29             GenericParamDefKind::Const => "constant",
  30         }
  31     }
  32     pub fn to_ord(&self, tcx: TyCtxt<'_>) -> ast::ParamKindOrd {
  33         match self {
  34             GenericParamDefKind::Lifetime => ast::ParamKindOrd::Lifetime,
  35             GenericParamDefKind::Type { .. } => ast::ParamKindOrd::Type,
  36             GenericParamDefKind::Const => {
  37                 ast::ParamKindOrd::Const { unordered: tcx.features().const_generics }
  38             }
  39         }
  40     }
  41 }
  42
  43 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
  44 pub struct GenericParamDef {
  45     pub name: Symbol,
  46     pub def_id: DefId,
  47     pub index: u32,
  48
  49     /// `pure_wrt_drop`, set by the (unsafe) `#[may_dangle]` attribute
  50     /// on generic parameter `'a`/`T`, asserts data behind the parameter
  51     /// `'a`/`T` won't be accessed during the parent type's `Drop` impl.
  52     pub pure_wrt_drop: bool,
  53
  54     pub kind: GenericParamDefKind,
  55 }
  56
  57 impl GenericParamDef {
  58     pub fn to_early_bound_region_data(&self) -> ty::EarlyBoundRegion {
  59         if let GenericParamDefKind::Lifetime = self.kind {
  60             ty::EarlyBoundRegion { def_id: self.def_id, index: self.index, name: self.name }
  61         } else {
  62             bug!("cannot convert a non-lifetime parameter def to an early bound region")
  63         }
  64     }
  65 }
  66
  67 #[derive(Default)]
  68 pub struct GenericParamCount {
  69     pub lifetimes: usize,
  70     pub types: usize,
  71     pub consts: usize,
  72 }
  73
  74 /// Information about the formal type/lifetime parameters associated
  75 /// with an item or method. Analogous to `hir::Generics`.
  76 ///
  77 /// The ordering of parameters is the same as in `Subst` (excluding child generics):
  78 /// `Self` (optionally), `Lifetime` params..., `Type` params...
  79 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
  80 pub struct Generics {
  81     pub parent: Option<DefId>,
  82     pub parent_count: usize,
  83     pub params: Vec<GenericParamDef>,
  84
  85     /// Reverse map to the `index` field of each `GenericParamDef`.
  86     #[stable_hasher(ignore)]
  87     pub param_def_id_to_index: FxHashMap<DefId, u32>,
  88
  89     pub has_self: bool,
  90     pub has_late_bound_regions: Option<Span>,
  91 }
  92
  93 impl<'tcx> Generics {
  94     pub fn count(&self) -> usize {
  95         self.parent_count + self.params.len()
  96     }
  97
  98     pub fn own_counts(&self) -> GenericParamCount {
  99         // We could cache this as a property of `GenericParamCount`, but
 100         // the aim is to refactor this away entirely eventually and the
 101         // presence of this method will be a constant reminder.
 102         let mut own_counts = GenericParamCount::default();
 103
 104         for param in &self.params {
 105             match param.kind {
 106                 GenericParamDefKind::Lifetime => own_counts.lifetimes += 1,
 107                 GenericParamDefKind::Type { .. } => own_counts.types += 1,
 108                 GenericParamDefKind::Const => own_counts.consts += 1,
 109             }
 110         }
 111
 112         own_counts
 113     }
 114
 115     pub fn own_defaults(&self) -> GenericParamCount {
 116         let mut own_defaults = GenericParamCount::default();
 117
 118         for param in &self.params {
 119             match param.kind {
 120                 GenericParamDefKind::Lifetime => (),
 121                 GenericParamDefKind::Type { has_default, .. } => {
 122                     own_defaults.types += has_default as usize;
 123                 }
 124                 GenericParamDefKind::Const => {
 125                     // FIXME(const_generics:defaults)
 126                 }
 127             }
 128         }
 129
 130         own_defaults
 131     }
 132
 133     pub fn requires_monomorphization(&self, tcx: TyCtxt<'tcx>) -> bool {
 134         if self.own_requires_monomorphization() {
 135             return true;
 136         }
 137
 138         if let Some(parent_def_id) = self.parent {
 139             let parent = tcx.generics_of(parent_def_id);
 140             parent.requires_monomorphization(tcx)
 141         } else {
 142             false
 143         }
 144     }
 145
 146     pub fn own_requires_monomorphization(&self) -> bool {
 147         for param in &self.params {
 148             match param.kind {
 149                 GenericParamDefKind::Type { .. } | GenericParamDefKind::Const => return true,
 150                 GenericParamDefKind::Lifetime => {}
 151             }
 152         }
 153         false
 154     }
 155
 156     /// Returns the `GenericParamDef` with the given index.
 157     pub fn param_at(&'tcx self, param_index: usize, tcx: TyCtxt<'tcx>) -> &'tcx GenericParamDef {
 158         if let Some(index) = param_index.checked_sub(self.parent_count) {
 159             &self.params[index]
 160         } else {
 161             tcx.generics_of(self.parent.expect("parent_count > 0 but no parent?"))
 162                 .param_at(param_index, tcx)
 163         }
 164     }
 165
 166     /// Returns the `GenericParamDef` associated with this `EarlyBoundRegion`.
 167     pub fn region_param(
 168         &'tcx self,
 169         param: &EarlyBoundRegion,
 170         tcx: TyCtxt<'tcx>,
 171     ) -> &'tcx GenericParamDef {
 172         let param = self.param_at(param.index as usize, tcx);
 173         match param.kind {
 174             GenericParamDefKind::Lifetime => param,
 175             _ => bug!("expected lifetime parameter, but found another generic parameter"),
 176         }
 177     }
 178
 179     /// Returns the `GenericParamDef` associated with this `ParamTy`.
 180     pub fn type_param(&'tcx self, param: &ParamTy, tcx: TyCtxt<'tcx>) -> &'tcx GenericParamDef {
 181         let param = self.param_at(param.index as usize, tcx);
 182         match param.kind {
 183             GenericParamDefKind::Type { .. } => param,
 184             _ => bug!("expected type parameter, but found another generic parameter"),
 185         }
 186     }
 187
 188     /// Returns the `GenericParamDef` associated with this `ParamConst`.
 189     pub fn const_param(&'tcx self, param: &ParamConst, tcx: TyCtxt<'tcx>) -> &GenericParamDef {
 190         let param = self.param_at(param.index as usize, tcx);
 191         match param.kind {
 192             GenericParamDefKind::Const => param,
 193             _ => bug!("expected const parameter, but found another generic parameter"),
 194         }
 195     }
 196 }
 197
 198 /// Bounds on generics.
 199 #[derive(Copy, Clone, Default, Debug, TyEncodable, TyDecodable, HashStable)]
 200 pub struct GenericPredicates<'tcx> {
 201     pub parent: Option<DefId>,
 202     pub predicates: &'tcx [(Predicate<'tcx>, Span)],
 203 }
 204
 205 impl<'tcx> GenericPredicates<'tcx> {
 206     pub fn instantiate(
 207         &self,
 208         tcx: TyCtxt<'tcx>,
 209         substs: SubstsRef<'tcx>,
 210     ) -> InstantiatedPredicates<'tcx> {
 211         let mut instantiated = InstantiatedPredicates::empty();
 212         self.instantiate_into(tcx, &mut instantiated, substs);
 213         instantiated
 214     }
 215
 216     pub fn instantiate_own(
 217         &self,
 218         tcx: TyCtxt<'tcx>,
 219         substs: SubstsRef<'tcx>,
 220     ) -> InstantiatedPredicates<'tcx> {
 221         InstantiatedPredicates {
 222             predicates: self.predicates.iter().map(|(p, _)| p.subst(tcx, substs)).collect(),
 223             spans: self.predicates.iter().map(|(_, sp)| *sp).collect(),
 224         }
 225     }
 226
 227     fn instantiate_into(
 228         &self,
 229         tcx: TyCtxt<'tcx>,
 230         instantiated: &mut InstantiatedPredicates<'tcx>,
 231         substs: SubstsRef<'tcx>,
 232     ) {
 233         if let Some(def_id) = self.parent {
 234             tcx.predicates_of(def_id).instantiate_into(tcx, instantiated, substs);
 235         }
 236         instantiated.predicates.extend(self.predicates.iter().map(|(p, _)| p.subst(tcx, substs)));
 237         instantiated.spans.extend(self.predicates.iter().map(|(_, sp)| *sp));
 238     }
 239
 240     pub fn instantiate_identity(&self, tcx: TyCtxt<'tcx>) -> InstantiatedPredicates<'tcx> {
 241         let mut instantiated = InstantiatedPredicates::empty();
 242         self.instantiate_identity_into(tcx, &mut instantiated);
 243         instantiated
 244     }
 245
 246     fn instantiate_identity_into(
 247         &self,
 248         tcx: TyCtxt<'tcx>,
 249         instantiated: &mut InstantiatedPredicates<'tcx>,
 250     ) {
 251         if let Some(def_id) = self.parent {
 252             tcx.predicates_of(def_id).instantiate_identity_into(tcx, instantiated);
 253         }
 254         instantiated.predicates.extend(self.predicates.iter().map(|(p, _)| p));
 255         instantiated.spans.extend(self.predicates.iter().map(|(_, s)| s));
 256     }
 257 }