pub struct DebruijnIndex {
    pub(crate) depth: u32,
}
Expand description

References the binder at the given depth. The index is a de Bruijn index, so it counts back through the in-scope binders, with 0 being the innermost binder. This is used in impls and the like. For example, if we had a rule like for<T> { (T: Clone) :- (T: Copy) }, then T would be represented as a BoundVar(0) (as the for is the innermost binder).

Fields

depth: u32

Implementations

Innermost index.

One level higher than the innermost index.

Creates a new de Bruijn index with a given depth.

Depth of the De Bruijn index, counting from 0 starting with the innermost binder.

True if the binder identified by this index is within the binder identified by the index outer_binder.

Example

Imagine you have the following binders in scope

forall<a> forall<b> forall<c>

then the Debruijn index for c would be 0, the index for b would be 1, and so on. Now consider the following calls:

  • c.within(a) = true
  • b.within(a) = true
  • a.within(a) = false
  • a.within(c) = false

Returns the resulting index when this value is moved into through one binder.

Update this index in place by shifting it “in” through amount number of binders.

Adds outer_binder levels to the self index. Intuitively, this shifts the self index, which was valid at the outer binder, so that it is valid at the innermost binder.

Example: Assume that the following binders are in scope:

for<A> for<B> for<C> for<D>
           ^ outer binder

Assume further that the outer_binder argument is 2, which means that it is referring to the for<B> binder (since D would be the innermost binder).

This means that self is relative to the binder B – so if self is 0 (INNERMOST), then it refers to B, and if self is 1, then it refers to A.

We will return as follows:

  • 0.shifted_in_from(2) = 2 – i.e., B, when shifted in to the binding level D, has index 2
  • 1.shifted_in_from(2) = 3 – i.e., A, when shifted in to the binding level D, has index 3
  • 2.shifted_in_from(1) = 3 – here, we changed the outer_binder to refer to C. Therefore 2 (relative to C) refers to A, so the result is still 3 (since A, relative to the innermost binder, has index 3).

Returns the resulting index when this value is moved out from amount number of new binders.

Update in place by shifting out from amount binders.

Subtracts outer_binder levels from the self index. Intuitively, this shifts the self index, which was valid at the innermost binder, to one that is valid at the binder outer_binder.

This will return None if the self index is internal to the outer binder (i.e., if self < outer_binder).

Example: Assume that the following binders are in scope:

for<A> for<B> for<C> for<D>
           ^ outer binder

Assume further that the outer_binder argument is 2, which means that it is referring to the for<B> binder (since D would be the innermost binder).

This means that the result is relative to the binder B – so if self is 0 (INNERMOST), then it refers to B, and if self is 1, then it refers to A.

We will return as follows:

  • 1.shifted_out_to(2) = None – i.e., the binder for C can’t be named from the binding level B
  • 3.shifted_out_to(2) = Some(1) – i.e., A, when shifted out to the binding level B, has index 1

Trait Implementations

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

Feeds this value into the given Hasher. Read more

Feeds a slice of this type into the given Hasher. Read more

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

Restrict a value to a certain interval. Read more

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

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

This method tests less than (for self and other) and is used by the < operator. Read more

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

This method tests greater than (for self and other) and is used by the > operator. Read more

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

Apply the given folder folder to self; binders is the number of binders that are in scope when beginning the folder. Typically binders starts as 0, but is adjusted when we encounter Binders<T> in the IR or other similar constructs. Read more

Apply the given visitor visitor to self; binders is the number of binders that are in scope when beginning the visitor. Typically binders starts as 0, but is adjusted when we encounter Binders<T> in the IR or other similar constructs. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Cast a value to type U using CastTo.

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

Shifts this term in one level of binders.

Shifts a term valid at outer_binder so that it is valid at the innermost binder. See DebruijnIndex::shifted_in_from for a detailed explanation. Read more

Shifts a term valid at the innermost binder so that it is valid at outer_binder. See DebruijnIndex::shifted_out_to for a detailed explanation. Read more

Shifts this term out one level of binders.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.

Check whether there are free (non-bound) variables.