crates/hir_ty/src/infer/path.rs

   1 //! Path expression resolution.
   2
   3 use std::iter;
   4
   5 use hir_def::{
   6     path::{Path, PathSegment},
   7     resolver::{ResolveValueResult, Resolver, TypeNs, ValueNs},
   8     AdtId, AssocContainerId, AssocItemId, EnumVariantId, Lookup,
   9 };
  10 use hir_expand::name::Name;
  11
  12 use crate::{
  13     method_resolution, to_chalk_trait_id, Interner, Substitution, Ty, TyKind, ValueTyDefId,
  14 };
  15
  16 use super::{ExprOrPatId, InferenceContext, TraitRef};
  17
  18 impl<'a> InferenceContext<'a> {
  19     pub(super) fn infer_path(
  20         &mut self,
  21         resolver: &Resolver,
  22         path: &Path,
  23         id: ExprOrPatId,
  24     ) -> Option<Ty> {
  25         let ty = self.resolve_value_path(resolver, path, id)?;
  26         let ty = self.insert_type_vars(ty);
  27         let ty = self.normalize_associated_types_in(ty);
  28         Some(ty)
  29     }
  30
  31     fn resolve_value_path(
  32         &mut self,
  33         resolver: &Resolver,
  34         path: &Path,
  35         id: ExprOrPatId,
  36     ) -> Option<Ty> {
  37         let (value, self_subst) = if let Some(type_ref) = path.type_anchor() {
  38             if path.segments().is_empty() {
  39                 // This can't actually happen syntax-wise
  40                 return None;
  41             }
  42             let ty = self.make_ty(type_ref);
  43             let remaining_segments_for_ty = path.segments().take(path.segments().len() - 1);
  44             let ctx = crate::lower::TyLoweringContext::new(self.db, &resolver);
  45             let (ty, _) = ctx.lower_ty_relative_path(ty, None, remaining_segments_for_ty);
  46             self.resolve_ty_assoc_item(
  47                 ty,
  48                 &path.segments().last().expect("path had at least one segment").name,
  49                 id,
  50             )?
  51         } else {
  52             let value_or_partial =
  53                 resolver.resolve_path_in_value_ns(self.db.upcast(), path.mod_path())?;
  54
  55             match value_or_partial {
  56                 ResolveValueResult::ValueNs(it) => (it, None),
  57                 ResolveValueResult::Partial(def, remaining_index) => {
  58                     self.resolve_assoc_item(def, path, remaining_index, id)?
  59                 }
  60             }
  61         };
  62
  63         let typable: ValueTyDefId = match value {
  64             ValueNs::LocalBinding(pat) => {
  65                 let ty = self.result.type_of_pat.get(pat)?.clone();
  66                 let ty = self.resolve_ty_as_possible(ty);
  67                 return Some(ty);
  68             }
  69             ValueNs::FunctionId(it) => it.into(),
  70             ValueNs::ConstId(it) => it.into(),
  71             ValueNs::StaticId(it) => it.into(),
  72             ValueNs::StructId(it) => {
  73                 self.write_variant_resolution(id, it.into());
  74
  75                 it.into()
  76             }
  77             ValueNs::EnumVariantId(it) => {
  78                 self.write_variant_resolution(id, it.into());
  79
  80                 it.into()
  81             }
  82             ValueNs::ImplSelf(impl_id) => {
  83                 let generics = crate::utils::generics(self.db.upcast(), impl_id.into());
  84                 let substs = Substitution::type_params_for_generics(self.db, &generics);
  85                 let ty = self.db.impl_self_ty(impl_id).subst(&substs);
  86                 if let Some((AdtId::StructId(struct_id), substs)) = ty.as_adt() {
  87                     let ty = self.db.value_ty(struct_id.into()).subst(&substs);
  88                     return Some(ty);
  89                 } else {
  90                     // FIXME: diagnostic, invalid Self reference
  91                     return None;
  92                 }
  93             }
  94             ValueNs::GenericParam(it) => return Some(self.db.const_param_ty(it)),
  95         };
  96
  97         let ty = self.db.value_ty(typable);
  98         // self_subst is just for the parent
  99         let parent_substs = self_subst.unwrap_or_else(Substitution::empty);
 100         let ctx = crate::lower::TyLoweringContext::new(self.db, &self.resolver);
 101         let substs = ctx.substs_from_path(path, typable, true);
 102         let full_substs = Substitution::builder(substs.len())
 103             .use_parent_substs(&parent_substs)
 104             .fill(substs.0[parent_substs.len()..].iter().cloned())
 105             .build();
 106         let ty = ty.subst(&full_substs);
 107         Some(ty)
 108     }
 109
 110     fn resolve_assoc_item(
 111         &mut self,
 112         def: TypeNs,
 113         path: &Path,
 114         remaining_index: usize,
 115         id: ExprOrPatId,
 116     ) -> Option<(ValueNs, Option<Substitution>)> {
 117         assert!(remaining_index < path.segments().len());
 118         // there may be more intermediate segments between the resolved one and
 119         // the end. Only the last segment needs to be resolved to a value; from
 120         // the segments before that, we need to get either a type or a trait ref.
 121
 122         let resolved_segment = path.segments().get(remaining_index - 1).unwrap();
 123         let remaining_segments = path.segments().skip(remaining_index);
 124         let is_before_last = remaining_segments.len() == 1;
 125
 126         match (def, is_before_last) {
 127             (TypeNs::TraitId(trait_), true) => {
 128                 let segment =
 129                     remaining_segments.last().expect("there should be at least one segment here");
 130                 let ctx = crate::lower::TyLoweringContext::new(self.db, &self.resolver);
 131                 let trait_ref =
 132                     ctx.lower_trait_ref_from_resolved_path(trait_, resolved_segment, None);
 133                 self.resolve_trait_assoc_item(trait_ref, segment, id)
 134             }
 135             (def, _) => {
 136                 // Either we already have a type (e.g. `Vec::new`), or we have a
 137                 // trait but it's not the last segment, so the next segment
 138                 // should resolve to an associated type of that trait (e.g. `<T
 139                 // as Iterator>::Item::default`)
 140                 let remaining_segments_for_ty =
 141                     remaining_segments.take(remaining_segments.len() - 1);
 142                 let ctx = crate::lower::TyLoweringContext::new(self.db, &self.resolver);
 143                 let (ty, _) = ctx.lower_partly_resolved_path(
 144                     def,
 145                     resolved_segment,
 146                     remaining_segments_for_ty,
 147                     true,
 148                 );
 149                 if let TyKind::Unknown = ty.interned(&Interner) {
 150                     return None;
 151                 }
 152
 153                 let ty = self.insert_type_vars(ty);
 154                 let ty = self.normalize_associated_types_in(ty);
 155
 156                 let segment =
 157                     remaining_segments.last().expect("there should be at least one segment here");
 158
 159                 self.resolve_ty_assoc_item(ty, &segment.name, id)
 160             }
 161         }
 162     }
 163
 164     fn resolve_trait_assoc_item(
 165         &mut self,
 166         trait_ref: TraitRef,
 167         segment: PathSegment<'_>,
 168         id: ExprOrPatId,
 169     ) -> Option<(ValueNs, Option<Substitution>)> {
 170         let trait_ = trait_ref.hir_trait_id();
 171         let item =
 172             self.db.trait_data(trait_).items.iter().map(|(_name, id)| (*id)).find_map(|item| {
 173                 match item {
 174                     AssocItemId::FunctionId(func) => {
 175                         if segment.name == &self.db.function_data(func).name {
 176                             Some(AssocItemId::FunctionId(func))
 177                         } else {
 178                             None
 179                         }
 180                     }
 181
 182                     AssocItemId::ConstId(konst) => {
 183                         if self
 184                             .db
 185                             .const_data(konst)
 186                             .name
 187                             .as_ref()
 188                             .map_or(false, |n| n == segment.name)
 189                         {
 190                             Some(AssocItemId::ConstId(konst))
 191                         } else {
 192                             None
 193                         }
 194                     }
 195                     AssocItemId::TypeAliasId(_) => None,
 196                 }
 197             })?;
 198         let def = match item {
 199             AssocItemId::FunctionId(f) => ValueNs::FunctionId(f),
 200             AssocItemId::ConstId(c) => ValueNs::ConstId(c),
 201             AssocItemId::TypeAliasId(_) => unreachable!(),
 202         };
 203
 204         self.write_assoc_resolution(id, item);
 205         Some((def, Some(trait_ref.substitution)))
 206     }
 207
 208     fn resolve_ty_assoc_item(
 209         &mut self,
 210         ty: Ty,
 211         name: &Name,
 212         id: ExprOrPatId,
 213     ) -> Option<(ValueNs, Option<Substitution>)> {
 214         if let TyKind::Unknown = ty.interned(&Interner) {
 215             return None;
 216         }
 217
 218         if let Some(result) = self.resolve_enum_variant_on_ty(&ty, name, id) {
 219             return Some(result);
 220         }
 221
 222         let canonical_ty = self.canonicalizer().canonicalize_ty(ty.clone());
 223         let krate = self.resolver.krate()?;
 224         let traits_in_scope = self.resolver.traits_in_scope(self.db.upcast());
 225
 226         method_resolution::iterate_method_candidates(
 227             &canonical_ty.value,
 228             self.db,
 229             self.trait_env.clone(),
 230             krate,
 231             &traits_in_scope,
 232             Some(name),
 233             method_resolution::LookupMode::Path,
 234             move |_ty, item| {
 235                 let (def, container) = match item {
 236                     AssocItemId::FunctionId(f) => {
 237                         (ValueNs::FunctionId(f), f.lookup(self.db.upcast()).container)
 238                     }
 239                     AssocItemId::ConstId(c) => {
 240                         (ValueNs::ConstId(c), c.lookup(self.db.upcast()).container)
 241                     }
 242                     AssocItemId::TypeAliasId(_) => unreachable!(),
 243                 };
 244                 let substs = match container {
 245                     AssocContainerId::ImplId(impl_id) => {
 246                         let impl_substs = Substitution::build_for_def(self.db, impl_id)
 247                             .fill(iter::repeat_with(|| self.table.new_type_var()))
 248                             .build();
 249                         let impl_self_ty = self.db.impl_self_ty(impl_id).subst(&impl_substs);
 250                         self.unify(&impl_self_ty, &ty);
 251                         Some(impl_substs)
 252                     }
 253                     AssocContainerId::TraitId(trait_) => {
 254                         // we're picking this method
 255                         let trait_substs = Substitution::build_for_def(self.db, trait_)
 256                             .push(ty.clone())
 257                             .fill(std::iter::repeat_with(|| self.table.new_type_var()))
 258                             .build();
 259                         self.obligations.push(super::Obligation::Trait(TraitRef {
 260                             trait_id: to_chalk_trait_id(trait_),
 261                             substitution: trait_substs.clone(),
 262                         }));
 263                         Some(trait_substs)
 264                     }
 265                     AssocContainerId::ModuleId(_) => None,
 266                 };
 267
 268                 self.write_assoc_resolution(id, item);
 269                 Some((def, substs))
 270             },
 271         )
 272     }
 273
 274     fn resolve_enum_variant_on_ty(
 275         &mut self,
 276         ty: &Ty,
 277         name: &Name,
 278         id: ExprOrPatId,
 279     ) -> Option<(ValueNs, Option<Substitution>)> {
 280         let (enum_id, subst) = match ty.as_adt() {
 281             Some((AdtId::EnumId(e), subst)) => (e, subst),
 282             _ => return None,
 283         };
 284         let enum_data = self.db.enum_data(enum_id);
 285         let local_id = enum_data.variant(name)?;
 286         let variant = EnumVariantId { parent: enum_id, local_id };
 287         self.write_variant_resolution(id, variant.into());
 288         Some((ValueNs::EnumVariantId(variant), Some(subst.clone())))
 289     }
 290 }