Skip to content

Implement GATs, step 2 #119

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 3 commits into from
May 9, 2018
Merged

Implement GATs, step 2 #119

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
869ff06
Refactor LowerWhereClause for multiple domain goals
tmandry May 7, 2018
a532519
Refactor LowerClause to permit multiple clauses
tmandry May 8, 2018
f709901
Handle multiple leaf goals in LowerGoal
tmandry May 8, 2018
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
107 changes: 74 additions & 33 deletions src/ir/lowering/mod.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,9 +3,10 @@ use std::collections::BTreeMap;
use chalk_parse::ast::*;
use lalrpop_intern::intern;

use cast::Cast;
use cast::{Cast, Caster};
use errors::*;
use ir::{self, Anonymize, ToParameter};
use itertools::Itertools;
use solve::SolverChoice;

mod test;
Expand Down Expand Up @@ -205,7 +206,7 @@ impl LowerProgram for Program {
impl_data.insert(item_id, d.lower_impl(&empty_env)?);
}
Item::Clause(ref clause) => {
custom_clauses.push(clause.lower_clause(&empty_env)?);
custom_clauses.extend(clause.lower_clause(&empty_env)?);
}
}
}
Expand Down Expand Up @@ -412,26 +413,31 @@ trait LowerWhereClauseVec<T> {

impl LowerWhereClauseVec<ir::DomainGoal> for [WhereClause] {
fn lower(&self, env: &Env) -> Result<Vec<ir::DomainGoal>> {
self.iter().map(|wc| wc.lower(env)).collect()
self.iter().flat_map(|wc| wc.lower(env).apply_result()).collect()
}
}

impl LowerWhereClauseVec<ir::QuantifiedDomainGoal> for [QuantifiedWhereClause] {
fn lower(&self, env: &Env) -> Result<Vec<ir::QuantifiedDomainGoal>> {
self.iter().map(|wc| wc.lower(env)).collect()
self.iter()
.flat_map(|wc| match wc.lower(env) {
Ok(v) => v.into_iter().map(Ok).collect(),
Err(e) => vec![Err(e)],
})
.collect()
}
}

trait LowerWhereClause<T> {
fn lower(&self, env: &Env) -> Result<T>;
fn lower(&self, env: &Env) -> Result<Vec<T>>;
}

/// Lowers a where-clause in the context of a clause (i.e. in "negative"
/// position); this is limited to the kinds of where-clauses users can actually
/// type in Rust and well-formedness checks.
impl LowerWhereClause<ir::DomainGoal> for WhereClause {
fn lower(&self, env: &Env) -> Result<ir::DomainGoal> {
Ok(match self {
fn lower(&self, env: &Env) -> Result<Vec<ir::DomainGoal>> {
let goal = match self {
WhereClause::Implemented { trait_ref } => {
ir::DomainGoal::Holds(ir::WhereClauseAtom::Implemented(trait_ref.lower(env)?))
}
Expand Down Expand Up @@ -478,17 +484,18 @@ impl LowerWhereClause<ir::DomainGoal> for WhereClause {
target: target.lower(env)?
})
}
})
};
Ok(vec![goal])
}
}

impl LowerWhereClause<ir::QuantifiedDomainGoal> for QuantifiedWhereClause {
fn lower(&self, env: &Env) -> Result<ir::QuantifiedDomainGoal> {
fn lower(&self, env: &Env) -> Result<Vec<ir::QuantifiedDomainGoal>> {
let parameter_kinds = self.parameter_kinds.iter().map(|pk| pk.lower());
let binders = env.in_binders(parameter_kinds, |env| {
Ok(self.where_clause.lower(env)?)
})?;
Ok(binders)
Ok(binders.into_iter().collect())
}
}

Expand All @@ -497,7 +504,7 @@ impl LowerWhereClause<ir::QuantifiedDomainGoal> for QuantifiedWhereClause {
/// can appear, because it includes all the sorts of things that the compiler
/// must verify.
impl LowerWhereClause<ir::LeafGoal> for WhereClause {
fn lower(&self, env: &Env) -> Result<ir::LeafGoal> {
fn lower(&self, env: &Env) -> Result<Vec<ir::LeafGoal>> {
Ok(match *self {
WhereClause::Implemented { .. }
| WhereClause::ProjectionEq { .. }
Expand All @@ -507,17 +514,17 @@ impl LowerWhereClause<ir::LeafGoal> for WhereClause {
| WhereClause::TyFromEnv { .. }
| WhereClause::TraitRefFromEnv { .. }
| WhereClause::Derefs { .. } => {
let g: ir::DomainGoal = self.lower(env)?;
g.cast()
let goals: Vec<ir::DomainGoal> = self.lower(env)?;
goals.into_iter().casted().collect()
}
WhereClause::UnifyTys { ref a, ref b } => ir::EqGoal {
WhereClause::UnifyTys { ref a, ref b } => vec![ir::EqGoal {
a: ir::ParameterKind::Ty(a.lower(env)?),
b: ir::ParameterKind::Ty(b.lower(env)?),
}.cast(),
WhereClause::UnifyLifetimes { ref a, ref b } => ir::EqGoal {
}.cast()],
WhereClause::UnifyLifetimes { ref a, ref b } => vec![ir::EqGoal {
a: ir::ParameterKind::Lifetime(a.lower(env)?),
b: ir::ParameterKind::Lifetime(b.lower(env)?),
}.cast(),
}.cast()],
WhereClause::TraitInScope { trait_name } => {
let id = match env.lookup(trait_name)? {
NameLookup::Type(id) => id,
Expand All @@ -528,7 +535,7 @@ impl LowerWhereClause<ir::LeafGoal> for WhereClause {
bail!(ErrorKind::NotTrait(trait_name));
}

ir::DomainGoal::InScope(id).cast()
vec![ir::DomainGoal::InScope(id).cast()]
}
})
}
Expand Down Expand Up @@ -831,13 +838,14 @@ impl LowerImpl for Impl {
}

trait LowerClause {
fn lower_clause(&self, env: &Env) -> Result<ir::ProgramClause>;
fn lower_clause(&self, env: &Env) -> Result<Vec<ir::ProgramClause>>;
}

impl LowerClause for Clause {
fn lower_clause(&self, env: &Env) -> Result<ir::ProgramClause> {
let implication = env.in_binders(self.all_parameters(), |env| {
let consequence: ir::DomainGoal = self.consequence.lower(env)?;
fn lower_clause(&self, env: &Env) -> Result<Vec<ir::ProgramClause>> {
let implications = env.in_binders(self.all_parameters(), |env| {
let consequences: Vec<ir::DomainGoal> = self.consequence.lower(env)?;

let mut conditions: Vec<ir::Goal> = self.conditions
.iter()
.map(|g| g.lower(env).map(|g| *g))
Expand All @@ -848,17 +856,27 @@ impl LowerClause for Clause {
// therefore reverse.
conditions.reverse();

Ok(ir::ProgramClauseImplication {
consequence,
conditions,
})
let implications = consequences
.into_iter()
.map(|consequence| ir::ProgramClauseImplication {
consequence,
conditions: conditions.clone(),
})
.collect::<Vec<_>>();
Ok(implications)
})?;

if implication.binders.is_empty() {
Ok(ir::ProgramClause::Implies(implication.value))
} else {
Ok(ir::ProgramClause::ForAll(implication))
}
let clauses = implications
.into_iter()
.map(|implication: ir::Binders<ir::ProgramClauseImplication>| {
if implication.binders.is_empty() {
ir::ProgramClause::Implies(implication.value)
} else {
ir::ProgramClause::ForAll(implication)
}
})
.collect();
Ok(clauses)
}
}

Expand Down Expand Up @@ -968,15 +986,22 @@ impl<'k> LowerGoal<Env<'k>> for Goal {
// `if (FromEnv(T: Trait)) { ... /* this part is untouched */ ... }`.
let where_clauses: Result<Vec<_>> =
wc.into_iter()
.map(|wc| Ok(wc.lower_clause(env)?.into_from_env_clause()))
.flat_map(|wc| wc.lower_clause(env).apply_result())
.map(|result| result.map(|wc| wc.into_from_env_clause()))
.collect();
Ok(Box::new(ir::Goal::Implies(where_clauses?, g.lower(env)?)))
}
Goal::And(g1, g2) => {
Ok(Box::new(ir::Goal::And(g1.lower(env)?, g2.lower(env)?)))
}
Goal::Not(g) => Ok(Box::new(ir::Goal::Not(g.lower(env)?))),
Goal::Leaf(wc) => Ok(Box::new(ir::Goal::Leaf(wc.lower(env)?))),
Goal::Leaf(wc) => {
// A where clause can lower to multiple leaf goals; wrap these in Goal::And.
Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Not certain about this yet

Copy link
Member

@scalexm scalexm May 8, 2018 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Seems good to me! Also you can use itertools::Itertools and write something like:

leaves.fold1(|goal, leaf| {
    ir::Goal::And(Box::new(goal), Box::new(ir::Goal::Leaf(leaf)))
}).expect("at least one goal");

(see for example here)

Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Bah, itertools should have called this method reduce. =)

let leaves = wc.lower(env)?.into_iter().map(ir::Goal::Leaf);
let goal = leaves.fold1(|goal, leaf| ir::Goal::And(Box::new(goal), Box::new(leaf)))
.expect("at least one goal");
Ok(Box::new(goal))
}
}
}
}
Expand Down Expand Up @@ -1006,3 +1031,19 @@ impl LowerQuantifiedGoal for Goal {
Ok(Box::new(ir::Goal::Quantified(quantifier_kind, subgoal)))
}
}

/// Lowers Result<Vec<T>> -> Vec<Result<T>>.
trait ApplyResult {
type Output;
fn apply_result(self) -> Self::Output;
}

impl<T> ApplyResult for Result<Vec<T>> {
type Output = Vec<Result<T>>;
fn apply_result(self) -> Self::Output {
match self {
Ok(v) => v.into_iter().map(Ok).collect(),
Err(e) => vec![Err(e)],
}
}
}
23 changes: 23 additions & 0 deletions src/ir/mod.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -687,6 +687,29 @@ impl<T> Binders<T> {
}
}

/// Allows iterating over a Binders<Vec<T>>, for instance.
/// Each element will include the same set of parameter bounds.
impl<V: IntoIterator> IntoIterator for Binders<V> {
type Item = Binders<<V as IntoIterator>::Item>;
type IntoIter = BindersIntoIterator<V>;

fn into_iter(self) -> Self::IntoIter {
BindersIntoIterator { iter: self.value.into_iter(), binders: self.binders }
}
}

pub struct BindersIntoIterator<V: IntoIterator> {
iter: <V as IntoIterator>::IntoIter,
binders: Vec<ParameterKind<()>>,
}

impl<V: IntoIterator> Iterator for BindersIntoIterator<V> {
type Item = Binders<<V as IntoIterator>::Item>;
fn next(&mut self) -> Option<Self::Item> {
self.iter.next().map(|v| Binders { binders: self.binders.clone(), value: v })
}
}

/// Represents one clause of the form `consequence :- conditions` where
/// `conditions = cond_1 && cond_2 && ...` is the conjunction of the individual
/// conditions.
Expand Down