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|
//! This module is concerned with finding methods that a given type provides.
//! For details about how this works in rustc, see the method lookup page in the
//! [rustc guide](https://rust-lang.github.io/rustc-guide/method-lookup.html)
//! and the corresponding code mostly in librustc_typeck/check/method/probe.rs.
use std::sync::Arc;
use rustc_hash::FxHashMap;
use crate::{
HirDatabase, Module, Crate, Name, Function, Trait,
ids::TraitId,
impl_block::{ImplId, ImplBlock, ImplItem},
ty::{Ty, TypeCtor},
nameres::CrateModuleId,
};
/// This is used as a key for indexing impls.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum TyFingerprint {
Apply(TypeCtor),
}
impl TyFingerprint {
/// Creates a TyFingerprint for looking up an impl. Only certain types can
/// have impls: if we have some `struct S`, we can have an `impl S`, but not
/// `impl &S`. Hence, this will return `None` for reference types and such.
fn for_impl(ty: &Ty) -> Option<TyFingerprint> {
match ty {
Ty::Apply(a_ty) => Some(TyFingerprint::Apply(a_ty.ctor)),
_ => None,
}
}
}
#[derive(Debug, PartialEq, Eq)]
pub struct CrateImplBlocks {
/// To make sense of the CrateModuleIds, we need the source root.
krate: Crate,
impls: FxHashMap<TyFingerprint, Vec<(CrateModuleId, ImplId)>>,
impls_by_trait: FxHashMap<TraitId, Vec<(CrateModuleId, ImplId)>>,
}
impl CrateImplBlocks {
pub fn lookup_impl_blocks<'a>(&'a self, ty: &Ty) -> impl Iterator<Item = ImplBlock> + 'a {
let fingerprint = TyFingerprint::for_impl(ty);
fingerprint.and_then(|f| self.impls.get(&f)).into_iter().flat_map(|i| i.iter()).map(
move |(module_id, impl_id)| {
let module = Module { krate: self.krate, module_id: *module_id };
ImplBlock::from_id(module, *impl_id)
},
)
}
pub fn lookup_impl_blocks_for_trait<'a>(
&'a self,
tr: &Trait,
) -> impl Iterator<Item = ImplBlock> + 'a {
let id = tr.id;
self.impls_by_trait.get(&id).into_iter().flat_map(|i| i.iter()).map(
move |(module_id, impl_id)| {
let module = Module { krate: self.krate, module_id: *module_id };
ImplBlock::from_id(module, *impl_id)
},
)
}
fn collect_recursive(&mut self, db: &impl HirDatabase, module: &Module) {
let module_impl_blocks = db.impls_in_module(module.clone());
for (impl_id, _) in module_impl_blocks.impls.iter() {
let impl_block = ImplBlock::from_id(module_impl_blocks.module, impl_id);
let target_ty = impl_block.target_ty(db);
if let Some(target_ty_fp) = TyFingerprint::for_impl(&target_ty) {
self.impls
.entry(target_ty_fp)
.or_insert_with(Vec::new)
.push((module.module_id, impl_id));
}
if let Some(tr) = impl_block.target_trait(db) {
self.impls_by_trait
.entry(tr.id)
.or_insert_with(Vec::new)
.push((module.module_id, impl_id));
}
}
for child in module.children(db) {
self.collect_recursive(db, &child);
}
}
pub(crate) fn impls_in_crate_query(
db: &impl HirDatabase,
krate: Crate,
) -> Arc<CrateImplBlocks> {
let mut crate_impl_blocks = CrateImplBlocks {
krate,
impls: FxHashMap::default(),
impls_by_trait: FxHashMap::default(),
};
if let Some(module) = krate.root_module(db) {
crate_impl_blocks.collect_recursive(db, &module);
}
Arc::new(crate_impl_blocks)
}
}
fn def_crate(db: &impl HirDatabase, ty: &Ty) -> Option<Crate> {
match ty {
Ty::Apply(a_ty) => match a_ty.ctor {
TypeCtor::Adt(def_id) => def_id.krate(db),
_ => None,
},
_ => None,
}
}
impl Ty {
// FIXME: cache this as a query?
// - if so, what signature? (TyFingerprint, Name)?
// - or maybe cache all names and def_ids of methods per fingerprint?
/// Look up the method with the given name, returning the actual autoderefed
/// receiver type (but without autoref applied yet).
pub fn lookup_method(self, db: &impl HirDatabase, name: &Name) -> Option<(Ty, Function)> {
self.iterate_methods(db, |ty, f| {
let sig = f.signature(db);
if sig.name() == name && sig.has_self_param() {
Some((ty.clone(), f))
} else {
None
}
})
}
// This would be nicer if it just returned an iterator, but that runs into
// lifetime problems, because we need to borrow temp `CrateImplBlocks`.
pub fn iterate_methods<T>(
self,
db: &impl HirDatabase,
mut callback: impl FnMut(&Ty, Function) -> Option<T>,
) -> Option<T> {
// For method calls, rust first does any number of autoderef, and then one
// autoref (i.e. when the method takes &self or &mut self). We just ignore
// the autoref currently -- when we find a method matching the given name,
// we assume it fits.
// Also note that when we've got a receiver like &S, even if the method we
// find in the end takes &self, we still do the autoderef step (just as
// rustc does an autoderef and then autoref again).
for derefed_ty in self.autoderef(db) {
let krate = match def_crate(db, &derefed_ty) {
Some(krate) => krate,
None => continue,
};
let impls = db.impls_in_crate(krate);
for impl_block in impls.lookup_impl_blocks(&derefed_ty) {
for item in impl_block.items(db) {
match item {
ImplItem::Method(f) => {
if let Some(result) = callback(&derefed_ty, f) {
return Some(result);
}
}
_ => {}
}
}
}
}
None
}
// This would be nicer if it just returned an iterator, but that runs into
// lifetime problems, because we need to borrow temp `CrateImplBlocks`.
pub fn iterate_impl_items<T>(
self,
db: &impl HirDatabase,
mut callback: impl FnMut(ImplItem) -> Option<T>,
) -> Option<T> {
let krate = def_crate(db, &self)?;
let impls = db.impls_in_crate(krate);
for impl_block in impls.lookup_impl_blocks(&self) {
for item in impl_block.items(db) {
if let Some(result) = callback(item) {
return Some(result);
}
}
}
None
}
}
|
