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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 ra_db::{Cancelable, SourceRootId};
use crate::{HirDatabase, DefId, module_tree::ModuleId, Module, Crate, Name, Function, impl_block::{ImplId, ImplBlock, ImplItem}};
use super::Ty;
/// This is used as a key for indexing impls.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum TyFingerprint {
Adt(DefId),
// we'll also want to index impls for primitive types etc.
}
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::Adt { def_id, .. } => Some(TyFingerprint::Adt(*def_id)),
_ => None,
}
}
}
#[derive(Debug, PartialEq, Eq)]
pub struct CrateImplBlocks {
/// To make sense of the ModuleIds, we need the source root.
source_root_id: SourceRootId,
impls: FxHashMap<TyFingerprint, Vec<(ModuleId, ImplId)>>,
}
impl CrateImplBlocks {
pub fn lookup_impl_blocks<'a>(
&'a self,
db: &'a impl HirDatabase,
ty: &Ty,
) -> impl Iterator<Item = Cancelable<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_impl_blocks = db.impls_in_module(self.source_root_id, *module_id);
Ok(ImplBlock::from_id(module_impl_blocks, *impl_id))
})
}
fn collect_recursive(&mut self, db: &impl HirDatabase, module: Module) -> Cancelable<()> {
let module_id = module.def_id.loc(db).module_id;
let module_impl_blocks = db.impls_in_module(self.source_root_id, module_id);
for (impl_id, impl_data) in module_impl_blocks.impls.iter() {
let impl_block = ImplBlock::from_id(Arc::clone(&module_impl_blocks), impl_id);
if let Some(_target_trait) = impl_data.target_trait() {
// ignore for now
} else {
let target_ty =
Ty::from_hir(db, &module, Some(&impl_block), impl_data.target_type());
if let Some(target_ty_fp) = TyFingerprint::for_impl(&target_ty) {
self.impls
.entry(target_ty_fp)
.or_insert_with(Vec::new)
.push((module_id, impl_id));
}
}
}
for child in module.children(db) {
self.collect_recursive(db, child)?;
}
Ok(())
}
pub(crate) fn impls_in_crate_query(
db: &impl HirDatabase,
krate: Crate,
) -> Cancelable<Arc<CrateImplBlocks>> {
let crate_graph = db.crate_graph();
let file_id = crate_graph.crate_root(krate.crate_id);
let source_root_id = db.file_source_root(file_id);
let mut crate_impl_blocks = CrateImplBlocks {
source_root_id,
impls: FxHashMap::default(),
};
if let Some(module) = krate.root_module(db) {
crate_impl_blocks.collect_recursive(db, module)?;
}
Ok(Arc::new(crate_impl_blocks))
}
}
fn def_crate(db: &impl HirDatabase, ty: &Ty) -> Option<Crate> {
match ty {
Ty::Adt { def_id, .. } => def_id.krate(db),
_ => None,
}
}
impl Ty {
// TODO: cache this as a query?
// - if so, what signature? (TyFingerprint, Name)?
// - or maybe cache all names and def_ids of methods per fingerprint?
pub fn lookup_method(self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<DefId>> {
self.iterate_methods(db, |f| {
let sig = f.signature(db);
if sig.name() == name && sig.has_self_param() {
Ok(Some(f.def_id()))
} else {
Ok(None)
}
})
}
// This would be nicer if it just returned an iterator, but that's really
// complicated with all the cancelable operations
pub fn iterate_methods<T>(
self,
db: &impl HirDatabase,
mut callback: impl FnMut(Function) -> Cancelable<Option<T>>,
) -> Cancelable<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(db, &derefed_ty) {
let impl_block = impl_block?;
for item in impl_block.items() {
match item {
ImplItem::Method(f) => {
if let Some(result) = callback(f.clone())? {
return Ok(Some(result));
}
}
_ => {}
}
}
}
}
Ok(None)
}
}
|
