Enum DeBruijnVar

pub enum DeBruijnVar<Id> {
    Bound(DeBruijnId, Id),
    Free(Id),
}

Type-level variable.

Variables are bound in groups. Each item has a top-level binding group in its generic_params field, and then inner binders are possible using the RegionBinder<T> and Binder<T> types. Each variable is linked to exactly one binder. The Id then identifies the specific variable among all those bound in that group.

For instance, we have the following:

fn f<'a, 'b>(x: for<'c> fn(&'b u8, &'c u16, for<'d> fn(&'b u32, &'c u64, &'d u128)) -> u64) {}
     ^^^^^^         ^^       ^       ^          ^^       ^        ^        ^
       |       inner binder  |       |     inner binder  |        |        |
 top-level binder            |       |                   |        |        |
                       Bound(1, b)   |              Bound(2, b)   |     Bound(0, d)
                                     |                            |
                                 Bound(0, c)                 Bound(1, c)

To make consumption easier for projects that don’t do heavy substitution, a micro-pass at the end changes the variables bound at the top-level (i.e. in the GenericParams of items) to be Free. This is an optional pass, we may add a flag to deactivate it. The example above becomes:

fn f<'a, 'b>(x: for<'c> fn(&'b u8, &'c u16, for<'d> fn(&'b u32, &'c u64, &'d u128)) -> u64) {}
     ^^^^^^         ^^       ^       ^          ^^       ^        ^        ^
       |       inner binder  |       |     inner binder  |        |        |
 top-level binder            |       |                   |        |        |
                          Free(b)    |                Free(b)     |     Bound(0, d)
                                     |                            |
                                 Bound(0, c)                 Bound(1, c)

At the moment only region variables can be bound in a non-top-level binder.

Variants

Bound(DeBruijnId, Id)

A variable attached to the nth binder, counting from the innermost.

Free(Id)

A variable attached to the outermost binder (the one on the item). As explained above, This is not used in charon internals, only as a micro-pass before exporting the crate data.

Implementations

impl<Id> DeBruijnVar<Id>

where Id: Copy,

pub fn new_at_zero(id: Id) -> Self

pub fn free(id: Id) -> Self

pub fn bound(index: DeBruijnId, id: Id) -> Self

pub fn incr(&self) -> Self

pub fn decr(&self) -> Self

pub fn bound_at_depth(&self, depth: DeBruijnId) -> Option<Id>

Returns the variable id if it is bound as the given depth.

pub fn bound_at_depth_mut(&mut self, depth: DeBruijnId) -> Option<&mut Id>

Returns the variable id if it is bound as the given depth.

pub fn move_out_from_depth(&self, depth: DeBruijnId) -> Option<Self>

Move the variable out of depth binders. Returns None if the variable is bound in one of these depth binders.

pub fn move_under_binders(&self, depth: DeBruijnId) -> Self

Move under depth binders.

Trait Implementations

impl<T: AstVisitable + Idx> AstVisitable for DeBruijnVar<T>

fn drive<V: VisitAst>(&self, v: &mut V) -> ControlFlow<V::Break>

Recursively visit this type with the provided visitor. This calls the visitor’s visit_$any method if it exists, otherwise visit_inner.

fn drive_mut<V: VisitAstMut>(&mut self, v: &mut V) -> ControlFlow<V::Break>

Recursively visit this type with the provided visitor. This calls the visitor’s visit_$any method if it exists, otherwise visit_inner.

fn name(&self) -> &'static str

The name of the type, used for debug logging.

fn dyn_visit<T: AstVisitable>(&self, f: impl FnMut(&T))

Visit all occurrences of that type inside self, in pre-order traversal.

fn dyn_visit_mut<T: AstVisitable>(&mut self, f: impl FnMut(&mut T))

Visit all occurrences of that type inside self, in pre-order traversal.

impl<Id: Clone> Clone for DeBruijnVar<Id>

fn clone(&self) -> DeBruijnVar<Id>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<Id: Debug> Debug for DeBruijnVar<Id>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de, Id> Deserialize<'de> for DeBruijnVar<Id>

where Id: Deserialize<'de>,

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<Id: Display> Display for DeBruijnVar<Id>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'s, Id, V> Drive<'s, V> for DeBruijnVar<Id>

where V: Visitor + Visit<'s, DeBruijnId> + Visit<'s, Id>,

fn drive_inner(&'s self, visitor: &mut V) -> ControlFlow<V::Break>

Call v.visit() on the immediate contents of self.

impl<'s, Id, V> DriveMut<'s, V> for DeBruijnVar<Id>

where V: Visitor + VisitMut<'s, DeBruijnId> + VisitMut<'s, Id>,

fn drive_inner_mut(&'s mut self, visitor: &mut V) -> ControlFlow<V::Break>

Call v.visit() on the immediate contents of self.

impl From<DeBruijnVar<ConstGenericVarId>> for ConstGeneric

fn from(x: ConstGenericDbVar) -> Self

Converts to this type from the input type.

impl From<DeBruijnVar<RegionId>> for Region

fn from(x: RegionDbVar) -> Self

Converts to this type from the input type.

impl From<DeBruijnVar<TraitClauseId>> for TraitRefKind

fn from(x: ClauseDbVar) -> Self

Converts to this type from the input type.

impl From<DeBruijnVar<TypeVarId>> for Ty

fn from(x: TypeDbVar) -> Self

Converts to this type from the input type.

impl From<DeBruijnVar<TypeVarId>> for TyKind

fn from(x: TypeDbVar) -> Self

Converts to this type from the input type.

impl<Id: Hash> Hash for DeBruijnVar<Id>

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<Id: Ord> Ord for DeBruijnVar<Id>

fn cmp(&self, other: &DeBruijnVar<Id>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<Id: PartialEq> PartialEq for DeBruijnVar<Id>

fn eq(&self, other: &DeBruijnVar<Id>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<Id: PartialOrd> PartialOrd for DeBruijnVar<Id>

fn partial_cmp(&self, other: &DeBruijnVar<Id>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<Id> Serialize for DeBruijnVar<Id>

where Id: Serialize,

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl<Id: Copy> Copy for DeBruijnVar<Id>

impl<Id: Eq> Eq for DeBruijnVar<Id>

impl<Id> StructuralPartialEq for DeBruijnVar<Id>