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|
//! Path expression resolution.
use super::{ExprOrPatId, InferenceContext, TraitRef};
use crate::{
db::HirDatabase,
resolve::{ResolveValueResult, Resolver, TypeNs, ValueNs},
ty::{Substs, Ty, TypableDef, TypeWalk},
AssocItem, HasGenericParams, Namespace, Path,
};
impl<'a, D: HirDatabase> InferenceContext<'a, D> {
pub(super) fn infer_path(
&mut self,
resolver: &Resolver,
path: &Path,
id: ExprOrPatId,
) -> Option<Ty> {
let ty = self.resolve_value_path(resolver, path, id)?;
let ty = self.insert_type_vars(ty);
let ty = self.normalize_associated_types_in(ty);
Some(ty)
}
fn resolve_value_path(
&mut self,
resolver: &Resolver,
path: &Path,
id: ExprOrPatId,
) -> Option<Ty> {
let (value, self_subst) = if let crate::PathKind::Type(type_ref) = &path.kind {
if path.segments.is_empty() {
// This can't actually happen syntax-wise
return None;
}
let ty = self.make_ty(type_ref);
let remaining_segments_for_ty = &path.segments[..path.segments.len() - 1];
let ty = Ty::from_type_relative_path(self.db, resolver, ty, remaining_segments_for_ty);
self.resolve_ty_assoc_item(
ty,
path.segments.last().expect("path had at least one segment"),
id,
)?
} else {
let value_or_partial = resolver.resolve_path_in_value_ns(self.db, &path)?;
match value_or_partial {
ResolveValueResult::ValueNs(it) => (it, None),
ResolveValueResult::Partial(def, remaining_index) => {
self.resolve_assoc_item(def, path, remaining_index, id)?
}
}
};
let typable: TypableDef = match value {
ValueNs::LocalBinding(pat) => {
let ty = self.result.type_of_pat.get(pat)?.clone();
let ty = self.resolve_ty_as_possible(&mut vec![], ty);
return Some(ty);
}
ValueNs::Function(it) => it.into(),
ValueNs::Const(it) => it.into(),
ValueNs::Static(it) => it.into(),
ValueNs::Struct(it) => it.into(),
ValueNs::EnumVariant(it) => it.into(),
};
let mut ty = self.db.type_for_def(typable, Namespace::Values);
if let Some(self_subst) = self_subst {
ty = ty.subst(&self_subst);
}
let substs = Ty::substs_from_path(self.db, &self.resolver, path, typable);
let ty = ty.subst(&substs);
Some(ty)
}
fn resolve_assoc_item(
&mut self,
def: TypeNs,
path: &Path,
remaining_index: usize,
id: ExprOrPatId,
) -> Option<(ValueNs, Option<Substs>)> {
assert!(remaining_index < path.segments.len());
// there may be more intermediate segments between the resolved one and
// the end. Only the last segment needs to be resolved to a value; from
// the segments before that, we need to get either a type or a trait ref.
let resolved_segment = &path.segments[remaining_index - 1];
let remaining_segments = &path.segments[remaining_index..];
let is_before_last = remaining_segments.len() == 1;
match (def, is_before_last) {
(TypeNs::Trait(trait_), true) => {
let segment =
remaining_segments.last().expect("there should be at least one segment here");
let trait_ref = TraitRef::from_resolved_path(
self.db,
&self.resolver,
trait_,
resolved_segment,
None,
);
self.resolve_trait_assoc_item(trait_ref, segment, id)
}
(def, _) => {
// Either we already have a type (e.g. `Vec::new`), or we have a
// trait but it's not the last segment, so the next segment
// should resolve to an associated type of that trait (e.g. `<T
// as Iterator>::Item::default`)
let remaining_segments_for_ty = &remaining_segments[..remaining_segments.len() - 1];
let ty = Ty::from_partly_resolved_hir_path(
self.db,
&self.resolver,
def,
resolved_segment,
remaining_segments_for_ty,
);
if let Ty::Unknown = ty {
return None;
}
let segment =
remaining_segments.last().expect("there should be at least one segment here");
self.resolve_ty_assoc_item(ty, segment, id)
}
}
}
fn resolve_trait_assoc_item(
&mut self,
trait_ref: TraitRef,
segment: &crate::path::PathSegment,
id: ExprOrPatId,
) -> Option<(ValueNs, Option<Substs>)> {
let trait_ = trait_ref.trait_;
let item = trait_.items(self.db).iter().copied().find_map(|item| match item {
AssocItem::Function(func) => {
if segment.name == func.name(self.db) {
Some(AssocItem::Function(func))
} else {
None
}
}
AssocItem::Const(konst) => {
if konst.name(self.db).map_or(false, |n| n == segment.name) {
Some(AssocItem::Const(konst))
} else {
None
}
}
AssocItem::TypeAlias(_) => None,
})?;
let def = match item {
AssocItem::Function(f) => ValueNs::Function(f),
AssocItem::Const(c) => ValueNs::Const(c),
AssocItem::TypeAlias(_) => unreachable!(),
};
let generics = item.generic_params(self.db);
let mut substs = Vec::with_capacity(generics.count_params_including_parent());
substs.extend(trait_ref.substs.iter().cloned());
substs.extend(std::iter::repeat(Ty::Unknown).take(generics.params.len()));
self.write_assoc_resolution(id, item);
Some((def, Some(substs.into())))
}
fn resolve_ty_assoc_item(
&mut self,
ty: Ty,
segment: &crate::path::PathSegment,
id: ExprOrPatId,
) -> Option<(ValueNs, Option<Substs>)> {
if let Ty::Unknown = ty {
return None;
}
let krate = self.resolver.krate()?;
// Find impl
// FIXME: consider trait candidates
let item = ty.clone().iterate_impl_items(self.db, krate, |item| match item {
AssocItem::Function(func) => {
if segment.name == func.name(self.db) {
Some(AssocItem::Function(func))
} else {
None
}
}
AssocItem::Const(konst) => {
if konst.name(self.db).map_or(false, |n| n == segment.name) {
Some(AssocItem::Const(konst))
} else {
None
}
}
AssocItem::TypeAlias(_) => None,
})?;
let def = match item {
AssocItem::Function(f) => ValueNs::Function(f),
AssocItem::Const(c) => ValueNs::Const(c),
AssocItem::TypeAlias(_) => unreachable!(),
};
let substs = self.find_self_types(&def, ty);
self.write_assoc_resolution(id, item);
Some((def, substs))
}
fn find_self_types(&self, def: &ValueNs, actual_def_ty: Ty) -> Option<Substs> {
if let ValueNs::Function(func) = def {
// We only do the infer if parent has generic params
let gen = func.generic_params(self.db);
if gen.count_parent_params() == 0 {
return None;
}
let impl_block = func.impl_block(self.db)?.target_ty(self.db);
let impl_block_substs = impl_block.substs()?;
let actual_substs = actual_def_ty.substs()?;
let mut new_substs = vec![Ty::Unknown; gen.count_parent_params()];
// The following code *link up* the function actual parma type
// and impl_block type param index
impl_block_substs.iter().zip(actual_substs.iter()).for_each(|(param, pty)| {
if let Ty::Param { idx, .. } = param {
if let Some(s) = new_substs.get_mut(*idx as usize) {
*s = pty.clone();
}
}
});
Some(Substs(new_substs.into()))
} else {
None
}
}
}
|
