Struct chalk_ir::SubstFolder

pub(crate) struct SubstFolder<'i, I: Interner, A: AsParameters<I>> {
    pub(crate) interner: I,
    pub(crate) subst: &'i A,
}

Fields

interner: I

subst: &'i A

Implementations

impl<I: Interner, A: AsParameters<I>> SubstFolder<'_, I, A>

pub fn at(&self, index: usize) -> &GenericArg<I>

Index into the list of parameters.

Trait Implementations

impl<'i, I: Interner, A: AsParameters<I>> TypeFolder<I> for &SubstFolder<'i, I, A>

type Error = NoSolution

The type this folder returns when folding fails. This is commonly NoSolution.

fn as_dyn(&mut self) -> &mut dyn TypeFolder<I, Error = Self::Error>

Creates a dyn value from this folder. Unfortunately, this must be added manually to each impl of TypeFolder; it permits the default implements below to create a &mut dyn TypeFolder from Self without knowing what Self is (by invoking this method). Effectively, this limits impls of TypeFolder to types for which we are able to create a dyn value (i.e., not [T] types).

fn fold_free_var_ty(
    &mut self,
    bound_var: BoundVar,
    outer_binder: DebruijnIndex
) -> Fallible<Ty<I>>

Invoked for TyKind::BoundVar instances that are not bound within the type being folded over:

fn fold_free_var_lifetime(
    &mut self,
    bound_var: BoundVar,
    outer_binder: DebruijnIndex
) -> Fallible<Lifetime<I>>

As fold_free_var_ty, but for lifetimes.

fn fold_free_var_const(
    &mut self,
    _ty: Ty<I>,
    bound_var: BoundVar,
    outer_binder: DebruijnIndex
) -> Fallible<Const<I>>

As fold_free_var_ty, but for constants.

fn interner(&self) -> I

Gets the interner that is being folded from.

fn fold_ty(
    &mut self,
    ty: Ty<I>,
    outer_binder: DebruijnIndex
) -> Result<Ty<I>, Self::Error>

Top-level callback: invoked for each Ty<I> that is encountered when folding. By default, invokes super_fold_with, which will in turn invoke the more specialized folding methods below, like fold_free_var_ty.

fn fold_lifetime(
    &mut self,
    lifetime: Lifetime<I>,
    outer_binder: DebruijnIndex
) -> Result<Lifetime<I>, Self::Error>

Top-level callback: invoked for each Lifetime<I> that is encountered when folding. By default, invokes super_fold_with, which will in turn invoke the more specialized folding methods below, like fold_free_var_lifetime.

fn fold_const(
    &mut self,
    constant: Const<I>,
    outer_binder: DebruijnIndex
) -> Result<Const<I>, Self::Error>

Top-level callback: invoked for each Const<I> that is encountered when folding. By default, invokes super_fold_with, which will in turn invoke the more specialized folding methods below, like fold_free_var_const.

fn fold_program_clause(
    &mut self,
    clause: ProgramClause<I>,
    outer_binder: DebruijnIndex
) -> Result<ProgramClause<I>, Self::Error>

Invoked for every program clause. By default, recursively folds the goals contents.

fn fold_goal(
    &mut self,
    goal: Goal<I>,
    outer_binder: DebruijnIndex
) -> Result<Goal<I>, Self::Error>

Invoked for every goal. By default, recursively folds the goals contents.

fn forbid_free_vars(&self) -> bool

If overridden to return true, then folding will panic if a free variable is encountered. This should be done if free type/lifetime variables are not expected.

fn forbid_free_placeholders(&self) -> bool

If overridden to return true, we will panic when a free placeholder type/lifetime/const is encountered.

fn fold_free_placeholder_ty(
    &mut self,
    universe: PlaceholderIndex,
    outer_binder: DebruijnIndex
) -> Result<Ty<I>, Self::Error>

Invoked for each occurrence of a placeholder type; these are used when we instantiate binders universally. Returns a type to use instead, which should be suitably shifted to account for binders.

fn fold_free_placeholder_lifetime(
    &mut self,
    universe: PlaceholderIndex,
    outer_binder: DebruijnIndex
) -> Result<Lifetime<I>, Self::Error>

As with fold_free_placeholder_ty, but for lifetimes.

fn fold_free_placeholder_const(
    &mut self,
    ty: Ty<I>,
    universe: PlaceholderIndex,
    outer_binder: DebruijnIndex
) -> Result<Const<I>, Self::Error>

As with fold_free_placeholder_ty, but for constants.

fn forbid_inference_vars(&self) -> bool

If overridden to return true, inference variables will trigger panics when folded. Used when inference variables are unexpected.

fn fold_inference_ty(
    &mut self,
    var: InferenceVar,
    kind: TyVariableKind,
    outer_binder: DebruijnIndex
) -> Result<Ty<I>, Self::Error>

Invoked for each occurrence of a inference type; these are used when we instantiate binders universally. Returns a type to use instead, which should be suitably shifted to account for binders.

fn fold_inference_lifetime(
    &mut self,
    var: InferenceVar,
    outer_binder: DebruijnIndex
) -> Result<Lifetime<I>, Self::Error>

As with fold_inference_ty, but for lifetimes.

fn fold_inference_const(
    &mut self,
    ty: Ty<I>,
    var: InferenceVar,
    outer_binder: DebruijnIndex
) -> Result<Const<I>, Self::Error>

As with fold_inference_ty, but for constants.