Trait hir_ty::TypeVisitor

pub trait TypeVisitor<I>
where
    I: Interner,
{
    type BreakTy;

    // Required methods
    fn as_dyn(&mut self) -> &mut dyn TypeVisitor<I, BreakTy = Self::BreakTy>;
    fn interner(&self) -> I;

    // Provided methods
    fn visit_ty(
        &mut self,
        ty: &Ty<I>,
        outer_binder: DebruijnIndex,
    ) -> ControlFlow<Self::BreakTy> { ... }
    fn visit_lifetime(
        &mut self,
        lifetime: &Lifetime<I>,
        outer_binder: DebruijnIndex,
    ) -> ControlFlow<Self::BreakTy> { ... }
    fn visit_const(
        &mut self,
        constant: &Const<I>,
        outer_binder: DebruijnIndex,
    ) -> ControlFlow<Self::BreakTy> { ... }
    fn visit_program_clause(
        &mut self,
        clause: &ProgramClause<I>,
        outer_binder: DebruijnIndex,
    ) -> ControlFlow<Self::BreakTy> { ... }
    fn visit_goal(
        &mut self,
        goal: &Goal<I>,
        outer_binder: DebruijnIndex,
    ) -> ControlFlow<Self::BreakTy> { ... }
    fn visit_domain_goal(
        &mut self,
        domain_goal: &DomainGoal<I>,
        outer_binder: DebruijnIndex,
    ) -> ControlFlow<Self::BreakTy> { ... }
    fn forbid_free_vars(&self) -> bool { ... }
    fn visit_free_var(
        &mut self,
        bound_var: BoundVar,
        outer_binder: DebruijnIndex,
    ) -> ControlFlow<Self::BreakTy> { ... }
    fn forbid_free_placeholders(&self) -> bool { ... }
    fn visit_free_placeholder(
        &mut self,
        universe: PlaceholderIndex,
        _outer_binder: DebruijnIndex,
    ) -> ControlFlow<Self::BreakTy> { ... }
    fn visit_where_clause(
        &mut self,
        where_clause: &WhereClause<I>,
        outer_binder: DebruijnIndex,
    ) -> ControlFlow<Self::BreakTy> { ... }
    fn forbid_inference_vars(&self) -> bool { ... }
    fn visit_inference_var(
        &mut self,
        var: InferenceVar,
        _outer_binder: DebruijnIndex,
    ) -> ControlFlow<Self::BreakTy> { ... }
}

A “visitor” recursively folds some term – that is, some bit of IR, such as a Goal, and computes a value as a result.

To apply a visitor, use the TypeVisitable::visit_with method, like so

let result = x.visit_with(&mut visitor, 0);

Required Associated Types

type BreakTy

The “break type” of the visitor, often (). It represents the result the visitor yields when it stops visiting.

Required Methods

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

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

fn interner(&self) -> I

Gets the visitor’s interner.

Provided Methods

fn visit_ty( &mut self, ty: &Ty<I>, outer_binder: DebruijnIndex, ) -> ControlFlow<Self::BreakTy>

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

fn visit_lifetime( &mut self, lifetime: &Lifetime<I>, outer_binder: DebruijnIndex, ) -> ControlFlow<Self::BreakTy>

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

fn visit_const( &mut self, constant: &Const<I>, outer_binder: DebruijnIndex, ) -> ControlFlow<Self::BreakTy>

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

fn visit_program_clause( &mut self, clause: &ProgramClause<I>, outer_binder: DebruijnIndex, ) -> ControlFlow<Self::BreakTy>

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

fn visit_goal( &mut self, goal: &Goal<I>, outer_binder: DebruijnIndex, ) -> ControlFlow<Self::BreakTy>

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

fn visit_domain_goal( &mut self, domain_goal: &DomainGoal<I>, outer_binder: DebruijnIndex, ) -> ControlFlow<Self::BreakTy>

Invoked for each domain goal.

fn forbid_free_vars(&self) -> bool

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

fn visit_free_var( &mut self, bound_var: BoundVar, outer_binder: DebruijnIndex, ) -> ControlFlow<Self::BreakTy>

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

fn forbid_free_placeholders(&self) -> bool

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

fn visit_free_placeholder( &mut self, universe: PlaceholderIndex, _outer_binder: DebruijnIndex, ) -> ControlFlow<Self::BreakTy>

Invoked for each occurrence of a placeholder type; these are used when we instantiate binders universally.

fn visit_where_clause( &mut self, where_clause: &WhereClause<I>, outer_binder: DebruijnIndex, ) -> ControlFlow<Self::BreakTy>

Invoked for each where clause.

fn forbid_inference_vars(&self) -> bool

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

fn visit_inference_var( &mut self, var: InferenceVar, _outer_binder: DebruijnIndex, ) -> ControlFlow<Self::BreakTy>

Invoked for each occurrence of a inference type; these are used when we instantiate binders universally.

Implementors