Struct rustc_trait_selection::solve::eval_ctxt::NestedGoals

pub(super) struct NestedGoals<'tcx> {
    pub(super) normalizes_to_hack_goal: Option<Goal<'tcx, ProjectionPredicate<'tcx>>>,
    pub(super) goals: Vec<Goal<'tcx, Predicate<'tcx>>>,
}

Fields

normalizes_to_hack_goal: Option<Goal<'tcx, ProjectionPredicate<'tcx>>>

This normalizes-to goal that is treated specially during the evaluation loop. In each iteration we take the RHS of the projection, replace it with a fresh inference variable, and only after evaluating that goal do we equate the fresh inference variable with the actual RHS of the predicate.

This is both to improve caching, and to avoid using the RHS of the projection predicate to influence the normalizes-to candidate we select.

This is not a ‘real’ nested goal. We must not forget to replace the RHS with a fresh inference variable when we evaluate this goal. That can result in a trait solver cycle. This would currently result in overflow but can be can be unsound with more powerful coinduction in the future.

goals: Vec<Goal<'tcx, Predicate<'tcx>>>

The rest of the goals which have not yet processed or remain ambiguous.

Implementations

impl NestedGoals<'_>

pub(super) fn new() -> Self

pub(super) fn is_empty(&self) -> bool

Trait Implementations

impl<'tcx> Clone for NestedGoals<'tcx>

fn clone(&self) -> NestedGoals<'tcx>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'tcx> Debug for NestedGoals<'tcx>

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

Formats the value using the given formatter.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 56 bytes