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//! Many kinds of items or constructs can have generic parameters: functions,
//! structs, impls, traits, etc. This module provides a common HIR for these
//! generic parameters. See also the `Generics` type and the `generics_of` query
//! in rustc.
use std::sync::Arc;
use hir_expand::name::{self, AsName, Name};
use ra_arena::Arena;
use ra_syntax::ast::{self, NameOwner, TypeBoundsOwner, TypeParamsOwner};
use crate::{
db::DefDatabase,
src::HasSource,
type_ref::{TypeBound, TypeRef},
AdtId, AstItemDef, GenericDefId, LocalGenericParamId, Lookup,
};
/// Data about a generic parameter (to a function, struct, impl, ...).
#[derive(Clone, PartialEq, Eq, Debug)]
pub struct GenericParamData {
pub name: Name,
pub default: Option<TypeRef>,
}
/// Data about the generic parameters of a function, struct, impl, etc.
#[derive(Clone, PartialEq, Eq, Debug)]
pub struct GenericParams {
pub params: Arena<LocalGenericParamId, GenericParamData>,
pub where_predicates: Vec<WherePredicate>,
}
/// A single predicate from a where clause, i.e. `where Type: Trait`. Combined
/// where clauses like `where T: Foo + Bar` are turned into multiple of these.
/// It might still result in multiple actual predicates though, because of
/// associated type bindings like `Iterator<Item = u32>`.
#[derive(Clone, PartialEq, Eq, Debug)]
pub struct WherePredicate {
pub type_ref: TypeRef,
pub bound: TypeBound,
}
impl GenericParams {
pub(crate) fn generic_params_query(
db: &impl DefDatabase,
def: GenericDefId,
) -> Arc<GenericParams> {
Arc::new(GenericParams::new(db, def.into()))
}
fn new(db: &impl DefDatabase, def: GenericDefId) -> GenericParams {
let mut generics = GenericParams { params: Arena::default(), where_predicates: Vec::new() };
// FIXME: add `: Sized` bound for everything except for `Self` in traits
match def {
GenericDefId::FunctionId(it) => generics.fill(&it.lookup(db).source(db).value),
GenericDefId::AdtId(AdtId::StructId(it)) => generics.fill(&it.source(db).value),
GenericDefId::AdtId(AdtId::UnionId(it)) => generics.fill(&it.source(db).value),
GenericDefId::AdtId(AdtId::EnumId(it)) => generics.fill(&it.source(db).value),
GenericDefId::TraitId(it) => {
// traits get the Self type as an implicit first type parameter
generics.params.alloc(GenericParamData { name: name::SELF_TYPE, default: None });
generics.fill(&it.source(db).value);
// add super traits as bounds on Self
// i.e., trait Foo: Bar is equivalent to trait Foo where Self: Bar
let self_param = TypeRef::Path(name::SELF_TYPE.into());
generics.fill_bounds(&it.source(db).value, self_param);
}
GenericDefId::TypeAliasId(it) => generics.fill(&it.lookup(db).source(db).value),
// Note that we don't add `Self` here: in `impl`s, `Self` is not a
// type-parameter, but rather is a type-alias for impl's target
// type, so this is handled by the resolver.
GenericDefId::ImplId(it) => generics.fill(&it.source(db).value),
GenericDefId::EnumVariantId(_) | GenericDefId::ConstId(_) => {}
}
generics
}
fn fill(&mut self, node: &impl TypeParamsOwner) {
if let Some(params) = node.type_param_list() {
self.fill_params(params)
}
if let Some(where_clause) = node.where_clause() {
self.fill_where_predicates(where_clause);
}
}
fn fill_bounds(&mut self, node: &impl ast::TypeBoundsOwner, type_ref: TypeRef) {
for bound in
node.type_bound_list().iter().flat_map(|type_bound_list| type_bound_list.bounds())
{
self.add_where_predicate_from_bound(bound, type_ref.clone());
}
}
fn fill_params(&mut self, params: ast::TypeParamList) {
for type_param in params.type_params() {
let name = type_param.name().map_or_else(Name::missing, |it| it.as_name());
// FIXME: Use `Path::from_src`
let default = type_param.default_type().map(TypeRef::from_ast);
let param = GenericParamData { name: name.clone(), default };
self.params.alloc(param);
let type_ref = TypeRef::Path(name.into());
self.fill_bounds(&type_param, type_ref);
}
}
fn fill_where_predicates(&mut self, where_clause: ast::WhereClause) {
for pred in where_clause.predicates() {
let type_ref = match pred.type_ref() {
Some(type_ref) => type_ref,
None => continue,
};
let type_ref = TypeRef::from_ast(type_ref);
for bound in pred.type_bound_list().iter().flat_map(|l| l.bounds()) {
self.add_where_predicate_from_bound(bound, type_ref.clone());
}
}
}
fn add_where_predicate_from_bound(&mut self, bound: ast::TypeBound, type_ref: TypeRef) {
if bound.has_question_mark() {
// FIXME: remove this bound
return;
}
let bound = TypeBound::from_ast(bound);
self.where_predicates.push(WherePredicate { type_ref, bound });
}
pub fn find_by_name(&self, name: &Name) -> Option<LocalGenericParamId> {
self.params.iter().find_map(|(id, p)| if &p.name == name { Some(id) } else { None })
}
}
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