crates/hir_ty/src/infer/path.rs

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