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Merged
merged 5 commits into from
May 10, 2018
Merged

Implement GATs, step 1 #118

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e490665
Remove where clauses on associated type values
tmandry May 5, 2018
23ec213
Add parse rules for GATs
tmandry May 6, 2018
3a6169e
Add support for + on GAT bounds
tmandry May 9, 2018
52c171e
Add parse rules for ProjectionEq bounds on GATs
tmandry May 9, 2018
0db2be9
Tweak inline bounds on associated types in the grammar
scalexm May 10, 2018
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3 changes: 2 additions & 1 deletion chalk-parse/src/ast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,8 @@ pub struct TraitFlags {
pub struct AssocTyDefn {
pub name: Identifier,
pub parameter_kinds: Vec<ParameterKind>,
pub bound: Option<TraitRef>,
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We would need multiple bounds there (see below), and using TraitRef is too rigid as we cannot parse things like type Foo<T>: Iterator<Item = T>.

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I'm thinking this would maybe need some slight refactoring for how we handle where clauses in the grammar. Something which may work would be to split existing where clauses like TraitRef into two parts: a left part (which would be T in T: Foo<K>) and a right part (which would be Foo<K>), separated by the : symbol. This would prevent code duplication I think because in the case of associated types, you would only ask for the right part and then build the whole TraitRef by hand as you did. It would be especially useful when we add lifetime requirements on types as well.

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Yep, what do you think of something like TraitBound and ProjectionEqBound that I added to ast? (Currently they're only being used for GATs.)

These can contain methods to convert them to TraitRef, WhereClause::ProjectionEq, etc. if the proper information is obtained.

pub where_clauses: Vec<QuantifiedWhereClause>,
}

pub enum ParameterKind {
Expand Down Expand Up @@ -115,7 +117,6 @@ pub struct Impl {
pub struct AssocTyValue {
pub name: Identifier,
pub parameter_kinds: Vec<ParameterKind>,
pub where_clauses: Vec<WhereClause>,
pub value: Ty,
}

Expand Down
31 changes: 21 additions & 10 deletions chalk-parse/src/parser.lalrpop
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Expand Up @@ -72,9 +72,26 @@ TraitDefn: TraitDefn = {
};

AssocTyDefn: AssocTyDefn = {
"type" <name:Id> <p:Angle<ParameterKind>> ";" => AssocTyDefn {
name: name,
parameter_kinds: p
"type" <name:Id> <p:Angle<ParameterKind>> <b:(":" <Id> <Angle<Parameter>>)?>
<w:QuantifiedWhereClauses> ";" =>
{
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Ok so currently we do not handle at all the + separator which expresses multiple bounds as in where T: Clone + Sized. This is not a problem for e.g. where clauses on traits because you can still write where T: Clone, T: Sized but for associated types since there is no other way to express these multiple bounds, we need to be able to parse them with the + acting as a separator.

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done

let bound = match b {
Some((t, a)) => {
let mut args = vec![Parameter::Ty(Ty::Id{ name })];
args.extend(a);
Some(TraitRef {
trait_name: t,
args: args,
})
}
None => None
};
AssocTyDefn {
name: name,
parameter_kinds: p,
where_clauses: w,
bound,
}
}
};

Expand Down Expand Up @@ -102,11 +119,10 @@ ParameterKind: ParameterKind = {
};

AssocTyValue: AssocTyValue = {
"type" <n:Id> <a:Angle<ParameterKind>> <wc:WhereClauses> "=" <v:Ty> ";" => AssocTyValue {
"type" <n:Id> <a:Angle<ParameterKind>> "=" <v:Ty> ";" => AssocTyValue {
name: n,
parameter_kinds: a,
value: v,
where_clauses: wc,
},
};

Expand Down Expand Up @@ -201,11 +217,6 @@ InlineClause: Clause = {
}
};

WhereClauses: Vec<WhereClause> = {
"where" <Comma<WhereClause>>,
() => vec![],
};

QuantifiedWhereClauses: Vec<QuantifiedWhereClause> = {
"where" <Comma<QuantifiedWhereClause>>,
() => vec![],
Expand Down
2 changes: 1 addition & 1 deletion src/fold/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -567,7 +567,7 @@ struct_fold!(AssociatedTyValue {
associated_ty_id,
value,
});
struct_fold!(AssociatedTyValueBound { ty, where_clauses });
struct_fold!(AssociatedTyValueBound { ty });
struct_fold!(Environment { clauses });
struct_fold!(InEnvironment[F] { environment, goal } where F: Fold<Result = F>);
struct_fold!(EqGoal { a, b });
Expand Down
1 change: 0 additions & 1 deletion src/ir/lowering/mod.rs
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Expand Up @@ -872,7 +872,6 @@ impl LowerAssocTyValue for AssocTyValue {
let value = env.in_binders(self.all_parameters(), |env| {
Ok(ir::AssociatedTyValueBound {
ty: self.value.lower(env)?,
where_clauses: self.where_clauses.lower(env)?,
})
})?;
Ok(ir::AssociatedTyValue {
Expand Down
34 changes: 32 additions & 2 deletions src/ir/lowering/test.rs
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Expand Up @@ -211,8 +211,7 @@ fn atc_accounting() {
AssociatedTyValue {
associated_ty_id: (Iterable::Iter),
value: for<lifetime> AssociatedTyValueBound {
ty: Iter<'?0, ?1>,
where_clauses: []
ty: Iter<'?0, ?1>
}
}
],
Expand Down Expand Up @@ -303,3 +302,34 @@ fn check_parameter_kinds() {
}
}
}

#[test]
fn gat_parse() {
let program = Arc::new(
parse_and_lower_program(
"
trait Sized {}

trait Foo {
type Item<'a, T>: Clone where Self: Sized;
}

trait Bar {
type Item<'a, T> where Self: Sized;
}

trait Baz {
type Item<'a, T>: Clone;
}

trait Quux {
type Item<'a, T>;
}
",
SolverChoice::slg()
).unwrap()
);
tls::set_current_program(&program, || {
println!("{:#?}", program.associated_ty_data.values());
});
}
4 changes: 0 additions & 4 deletions src/ir/mod.rs
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Expand Up @@ -289,10 +289,6 @@ pub struct AssociatedTyValue {
pub struct AssociatedTyValueBound {
/// Type that we normalize to. The X in `type Foo<'a> = X`.
crate ty: Ty,

/// Where-clauses that must hold for projection to be valid. The
/// WC in `type Foo<'a> = X where WC`.
crate where_clauses: Vec<DomainGoal>,
}

#[derive(Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
Expand Down
5 changes: 1 addition & 4 deletions src/rules/mod.rs
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Expand Up @@ -200,10 +200,7 @@ impl ir::AssociatedTyValue {
.trait_ref
.trait_ref()
.up_shift(self.value.len());
let conditions: Vec<ir::Goal> = Some(impl_trait_ref.clone().cast())
.into_iter()
.chain(self.value.value.where_clauses.clone().cast())
.collect();
let conditions: Vec<ir::Goal> = vec![impl_trait_ref.clone().cast()];

// Bound parameters + `Self` type of the trait-ref
let parameters: Vec<_> = {
Expand Down