Struct StackEntry 

pub(super) struct StackEntry<X: Cx> {
    pub input: X::Input,
    pub step_kind_from_parent: PathKind,
    pub available_depth: AvailableDepth,
    pub required_depth: usize,
    pub provisional_result: Option<X::Result>,
    pub heads: CycleHeads,
    pub encountered_overflow: bool,
    pub usages: Option<HeadUsages>,
    pub candidate_usages: Option<CandidateHeadUsages>,
    pub nested_goals: NestedGoals<X>,
}

Stack entries of the evaluation stack. Its fields tend to be lazily updated when popping a child goal or completely immutable.

Fields

input: X::Input

step_kind_from_parent: PathKind

Whether proving this goal is a coinductive step.

This is used when encountering a trait solver cycle to decide whether the initial provisional result of the cycle.

available_depth: AvailableDepth

The available depth of a given goal, immutable.

required_depth: usize

The maximum depth required while evaluating this goal.

provisional_result: Option<X::Result>

Starts out as None and gets set when rerunning this goal in case we encounter a cycle.

heads: CycleHeads

All cycle heads this goal depends on. Lazily updated and only up-to date for the top of the stack.

encountered_overflow: bool

Whether evaluating this goal encountered overflow. Lazily updated.

usages: Option<HeadUsages>

Whether and how this goal has been used as a cycle head. Lazily updated.

candidate_usages: Option<CandidateHeadUsages>

We want to be able to ignore head usages if they happen inside of candidates which don’t impact the result of a goal. This enables us to avoid rerunning goals and is also used when rebasing provisional cache entries.

To implement this, we track all usages while evaluating a candidate. If this candidate then ends up ignored, we manually remove its usages from usages and heads.

nested_goals: NestedGoals<X>

The nested goals of this goal, see the doc comment of the type.

Trait Implementations

impl<X> Debug for StackEntry<X>

where X: Cx,

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

Formats the value using the given formatter.

Layout

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.