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Add binders validator #694

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9 changes: 9 additions & 0 deletions chalk-ir/src/visit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -228,6 +228,15 @@ where
}
}

/// Invoked for each occurence of a `Binders`, before visiting them.
fn before_binders(&mut self, _kinds: &crate::VariableKinds<I>) {}
/// Invoked for each occurence of a `Canonical`, before visiting them.
fn before_canonical(&mut self, _kinds: &crate::CanonicalVarKinds<I>) {}
/// Invoked for each occurence of a `FnPointer`, before visiting them.
fn before_fn_pointer_substs(&mut self, _number: usize) {}
/// Invoked for each occurence of a type introducing binders, after visiting them.
fn after_any_binders(&mut self) {}

Comment on lines +231 to +239
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I wonder if it's worth just adding a visit_binders function like in rustc? (Probably) Is it all helpful to have these split out? I don't know if rustc calls visit_binder for fn pointer substs or canonical items, but we should.

Unfortunately, I think that our visit_binders would have to look like fn visit_binder<T: SuperVisit<I>>(&mut self, binders: crate::VariableKinds<I>, value: T) -> ControlFlow<Self::BreakTy>);, but that's probably fine.

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Alternatively, we could just change this to only have before_binders and do the "into VariableKinds conversion" happen before calling it.

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I tried something like that first, the problem is that it makes the Visitor trait not object safe.

We could do the before_binders, but it'd mean doing the conversion in every visitor instead of just the one where it's necessary.

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Well, I mean, you only need to do the conversion in the Visit impls, right?

/// Gets the visitor's interner.
fn interner(&self) -> &'i I;
}
Expand Down
20 changes: 15 additions & 5 deletions chalk-ir/src/visit/binder_impls.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,14 +15,18 @@ impl<I: Interner> Visit<I> for FnPointer<I> {
where
I: 'i,
{
self.substitution
.visit_with(visitor, outer_binder.shifted_in())
visitor.before_fn_pointer_substs(self.num_binders);
let result = self
.substitution
.visit_with(visitor, outer_binder.shifted_in());
visitor.after_any_binders();
result
}
}

impl<T, I: Interner> Visit<I> for Binders<T>
where
T: HasInterner + Visit<I>,
T: HasInterner<Interner = I> + Visit<I>,
{
fn visit_with<'i, B>(
&self,
Expand All @@ -32,7 +36,10 @@ where
where
I: 'i,
{
self.value.visit_with(visitor, outer_binder.shifted_in())
visitor.before_binders(&self.binders);
let result = self.value.visit_with(visitor, outer_binder.shifted_in());
visitor.after_any_binders();
result
}
}

Expand All @@ -49,6 +56,9 @@ where
where
I: 'i,
{
self.value.visit_with(visitor, outer_binder.shifted_in())
visitor.before_canonical(&self.binders);
let result = self.value.visit_with(visitor, outer_binder.shifted_in());
visitor.after_any_binders();
result
}
}
130 changes: 130 additions & 0 deletions chalk-ir/src/visit/visitors.rs
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Expand Up @@ -12,6 +12,18 @@ pub trait VisitExt<I: Interner>: Visit<I> {
)
.is_break()
}

/// Validates binders.
fn validate_binders(&self, interner: &I) -> bool {
self.visit_with(
&mut binders_check::BindersValidator {
interner,
stack: Vec::new(),
},
DebruijnIndex::INNERMOST,
)
.is_continue()
}
}

impl<T, I: Interner> VisitExt<I> for T where T: Visit<I> {}
Expand Down Expand Up @@ -39,3 +51,121 @@ impl<'i, I: Interner> Visitor<'i, I> for FindFreeVarsVisitor<'i, I> {
ControlFlow::BREAK
}
}

mod binders_check {
use crate::{
interner::Interner,
visit::{ControlFlow, SuperVisit, Visitor},
Const, DebruijnIndex, Lifetime, Ty, VariableKind,
};

pub struct BindersValidator<'i, I: Interner> {
pub(crate) interner: &'i I,
pub(crate) stack: Vec<Vec<VariableKind<I>>>,
}

impl<'i, I: Interner> Visitor<'i, I> for BindersValidator<'i, I> {
type BreakTy = ();

fn as_dyn(&mut self) -> &mut dyn Visitor<'i, I, BreakTy = Self::BreakTy> {
self
}

fn interner(&self) -> &'i I {
self.interner
}

fn visit_ty(
&mut self,
ty: &Ty<I>,
outer_binder: DebruijnIndex,
) -> ControlFlow<Self::BreakTy> {
if let Some(bv) = ty.bound_var(self.interner) {
assert_eq!(self.stack.len(), outer_binder.depth() as usize);
if bv.debruijn < outer_binder {
let kinds = &self.stack[self.stack.len() - 1 - bv.debruijn.depth() as usize];
match kinds.get(bv.index) {
Some(VariableKind::Ty(_)) => {}
_ => {
return ControlFlow::BREAK;
}
}
} else {
return ControlFlow::BREAK;
}
}
ty.super_visit_with(self.as_dyn(), outer_binder)
}

fn visit_const(
&mut self,
constant: &Const<I>,
outer_binder: DebruijnIndex,
) -> ControlFlow<Self::BreakTy> {
if let Some(bv) = constant.bound_var(self.interner) {
assert_eq!(self.stack.len(), outer_binder.depth() as usize);
if bv.debruijn < outer_binder {
let kinds = &self.stack[self.stack.len() - 1 - bv.debruijn.depth() as usize];
match kinds.get(bv.index) {
Some(VariableKind::Const(_ty)) => {
// FIXME: validate that type can match?
}
_ => {
return ControlFlow::BREAK;
}
}
} else {
return ControlFlow::BREAK;
}
}
constant.super_visit_with(self.as_dyn(), outer_binder)
}

fn visit_lifetime(
&mut self,
lifetime: &Lifetime<I>,
outer_binder: DebruijnIndex,
) -> ControlFlow<Self::BreakTy> {
if let Some(bv) = lifetime.bound_var(self.interner) {
assert_eq!(self.stack.len(), outer_binder.depth() as usize);
if bv.debruijn < outer_binder {
let kinds = &self.stack[self.stack.len() - 1 - bv.debruijn.depth() as usize];
match kinds.get(bv.index) {
Some(VariableKind::Lifetime) => {}
_ => {
return ControlFlow::BREAK;
}
}
} else {
return ControlFlow::BREAK;
}
}
lifetime.super_visit_with(self.as_dyn(), outer_binder)
}

fn before_binders(&mut self, kinds: &crate::VariableKinds<I>) {
self.stack.push(kinds.as_slice(self.interner).to_vec());
}

fn before_canonical(&mut self, kinds: &crate::CanonicalVarKinds<I>) {
self.stack.push(
kinds
.iter(self.interner)
.map(|wk| wk.kind.clone())
.collect(),
);
}

fn before_fn_pointer_substs(&mut self, number: usize) {
self.stack.push(
std::iter::repeat_with(|| VariableKind::Lifetime)
.take(number)
.collect(),
)
}

fn after_any_binders(&mut self) {
self.stack.pop().unwrap();
}
}
}
4 changes: 2 additions & 2 deletions chalk-solve/src/clauses/builtin_traits/unsize.rs
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Expand Up @@ -59,7 +59,7 @@ impl<'a, I: Interner> Visitor<'a, I> for UnsizeParameterCollector<'a, I> {

fn outer_binder_parameters_used<I: Interner>(
interner: &I,
v: &Binders<impl Visit<I> + HasInterner>,
v: &Binders<impl Visit<I> + HasInterner<Interner = I>>,
) -> HashSet<usize> {
let mut visitor = UnsizeParameterCollector {
interner,
Expand Down Expand Up @@ -123,7 +123,7 @@ impl<'a, 'p, I: Interner> Visitor<'a, I> for ParameterOccurenceCheck<'a, 'p, I>

fn uses_outer_binder_params<I: Interner>(
interner: &I,
v: &Binders<impl Visit<I> + HasInterner>,
v: &Binders<impl Visit<I> + HasInterner<Interner = I>>,
parameters: &HashSet<usize>,
) -> bool {
let mut visitor = ParameterOccurenceCheck {
Expand Down