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Higher-ranked trait bounds for where clauses

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This commit is contained in:
Lukas Wirth 2020-12-17 22:01:42 +01:00
parent c8c58d81ec
commit fa65d6ba85
4 changed files with 74 additions and 18 deletions
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37
crates/hir_def/src/generics.rs
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@ -62,6 +62,7 @@ pub struct GenericParams {
pub enum WherePredicate {
TypeBound { target: WherePredicateTypeTarget, bound: TypeBound },
Lifetime { target: LifetimeRef, bound: LifetimeRef },
ForLifetime { lifetimes: Box<[Name]>, target: WherePredicateTypeTarget, bound: TypeBound },
}
#[derive(Clone, PartialEq, Eq, Debug)]
@ -69,7 +70,6 @@ pub enum WherePredicateTypeTarget {
TypeRef(TypeRef),
/// For desugared where predicates that can directly refer to a type param.
TypeParam(LocalTypeParamId),
// FIXME: ForLifetime(Vec<LifetimeParamId>, TypeRef)
}
#[derive(Default)]
@ -234,7 +234,7 @@ impl GenericParams {
for bound in
node.type_bound_list().iter().flat_map(|type_bound_list| type_bound_list.bounds())
{
self.add_where_predicate_from_bound(lower_ctx, bound, target.clone());
self.add_where_predicate_from_bound(lower_ctx, bound, None, target.clone());
}
}
@ -279,8 +279,25 @@ impl GenericParams {
} else {
continue;
};
let lifetimes: Option<Box<_>> = pred.generic_param_list().map(|param_list| {
// Higher-Ranked Trait Bounds
param_list
.lifetime_params()
.map(|lifetime_param| {
lifetime_param
.lifetime()
.map_or_else(Name::missing, |lt| Name::new_lifetime(&lt))
})
.collect()
});
for bound in pred.type_bound_list().iter().flat_map(|l| l.bounds()) {
self.add_where_predicate_from_bound(lower_ctx, bound, target.clone());
self.add_where_predicate_from_bound(
lower_ctx,
bound,
lifetimes.as_ref(),
target.clone(),
);
}
}
}
@ -289,6 +306,7 @@ impl GenericParams {
&mut self,
lower_ctx: &LowerCtx,
bound: ast::TypeBound,
hrtb_lifetimes: Option<&Box<[Name]>>,
target: Either<TypeRef, LifetimeRef>,
) {
if bound.question_mark_token().is_some() {
@ -297,9 +315,16 @@ impl GenericParams {
}
let bound = TypeBound::from_ast(lower_ctx, bound);
let predicate = match (target, bound) {
(Either::Left(type_ref), bound) => WherePredicate::TypeBound {
target: WherePredicateTypeTarget::TypeRef(type_ref),
bound,
(Either::Left(type_ref), bound) => match hrtb_lifetimes {
Some(hrtb_lifetimes) => WherePredicate::ForLifetime {
lifetimes: hrtb_lifetimes.clone(),
target: WherePredicateTypeTarget::TypeRef(type_ref),
bound,
},
None => WherePredicate::TypeBound {
target: WherePredicateTypeTarget::TypeRef(type_ref),
bound,
},
},
(Either::Right(lifetime), TypeBound::Lifetime(bound)) => {
WherePredicate::Lifetime { target: lifetime, bound }