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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_syntax::ast::{self, NameOwner, TypeBoundsOwner, TypeParamsOwner};
use crate::{
db::DefDatabase2,
type_ref::{TypeBound, TypeRef},
AdtId, AstItemDef, GenericDefId, HasSource, Lookup,
};
/// Data about a generic parameter (to a function, struct, impl, ...).
#[derive(Clone, PartialEq, Eq, Debug)]
pub struct GenericParam {
// FIXME: give generic params proper IDs
pub idx: u32,
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 def: GenericDefId,
pub parent_params: Option<Arc<GenericParams>>,
pub params: Vec<GenericParam>,
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 fn new(
db: &impl DefDatabase2,
def: GenericDefId,
parent_params: Option<Arc<GenericParams>>,
) -> GenericParams {
let mut generics =
GenericParams { def, params: Vec::new(), parent_params, where_predicates: Vec::new() };
let start = generics.parent_params.as_ref().map(|p| p.params.len()).unwrap_or(0) as u32;
// FIXME: add `: Sized` bound for everything except for `Self` in traits
match def {
GenericDefId::FunctionId(it) => generics.fill(&it.lookup(db).source(db).value, start),
GenericDefId::AdtId(AdtId::StructId(it)) => {
generics.fill(&it.0.source(db).value, start)
}
GenericDefId::AdtId(AdtId::UnionId(it)) => generics.fill(&it.0.source(db).value, start),
GenericDefId::AdtId(AdtId::EnumId(it)) => generics.fill(&it.source(db).value, start),
GenericDefId::TraitId(it) => {
// traits get the Self type as an implicit first type parameter
generics.params.push(GenericParam {
idx: start,
name: name::SELF_TYPE,
default: None,
});
generics.fill(&it.source(db).value, start + 1);
// 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.source(db).value, start),
// 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, start),
GenericDefId::EnumVariantId(_) | GenericDefId::ConstId(_) => {}
}
generics
}
fn fill(&mut self, node: &impl TypeParamsOwner, start: u32) {
if let Some(params) = node.type_param_list() {
self.fill_params(params, start)
}
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, start: u32) {
for (idx, type_param) in params.type_params().enumerate() {
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 = GenericParam { idx: idx as u32 + start, name: name.clone(), default };
self.params.push(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<&GenericParam> {
self.params.iter().find(|p| &p.name == name)
}
pub fn count_parent_params(&self) -> usize {
self.parent_params.as_ref().map(|p| p.count_params_including_parent()).unwrap_or(0)
}
pub fn count_params_including_parent(&self) -> usize {
let parent_count = self.count_parent_params();
parent_count + self.params.len()
}
fn for_each_param<'a>(&'a self, f: &mut impl FnMut(&'a GenericParam)) {
if let Some(parent) = &self.parent_params {
parent.for_each_param(f);
}
self.params.iter().for_each(f);
}
pub fn params_including_parent(&self) -> Vec<&GenericParam> {
let mut vec = Vec::with_capacity(self.count_params_including_parent());
self.for_each_param(&mut |p| vec.push(p));
vec
}
}
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