# Struct rustc_trait_selection::solve::search_graph::SearchGraph

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    pub(super) struct SearchGraph<'tcx> {
        mode: SolverMode,
        stack: IndexVec<StackDepth, StackEntry<'tcx>>,
        provisional_cache: FxHashMap<CanonicalInput<'tcx>, ProvisionalCacheEntry<'tcx>>,
        cycle_participants: FxHashSet<CanonicalInput<'tcx>>,
    }

## Fields§

§`mode: SolverMode`§`stack: IndexVec<StackDepth, StackEntry<'tcx>>`

The stack of goals currently being computed.

An element is deeper in the stack if its index is lower.

§`provisional_cache: FxHashMap<CanonicalInput<'tcx>, ProvisionalCacheEntry<'tcx>>`§`cycle_participants: FxHashSet<CanonicalInput<'tcx>>`

We put only the root goal of a coinductive cycle into the global cache.

If we were to use that result when later trying to prove another cycle participant, we can end up with unstable query results.

See tests/ui/next-solver/coinduction/incompleteness-unstable-result.rs for an example of where this is needed.

## Implementations§

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### impl<'tcx> SearchGraph<'tcx>

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#### pub(super) fn new(mode: SolverMode) -> SearchGraph<'tcx>

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#### pub(super) fn solver_mode(&self) -> SolverMode

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#### fn on_cache_hit(&mut self, additional_depth: usize, encountered_overflow: bool)

Update the stack and reached depths on cache hits.

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#### fn pop_stack(&mut self) -> StackEntry<'tcx>

Pops the highest goal from the stack, lazily updating the the next goal in the stack.

Directly popping from the stack instead of using this method would cause us to not track overflow and recursion depth correctly.

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#### pub(super) fn global_cache( &self, tcx: TyCtxt<'tcx> ) -> &'tcx EvaluationCache<'tcx>

The trait solver behavior is different for coherence so we use a separate cache. Alternatively we could use a single cache and share it between coherence and ordinary trait solving.

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

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#### fn allowed_depth_for_nested( tcx: TyCtxt<'tcx>, stack: &IndexVec<StackDepth, StackEntry<'tcx>> ) -> Option<Limit>

Returns the remaining depth allowed for nested goals.

This is generally simply one less than the current depth. However, if we encountered overflow, we significantly reduce the remaining depth of all nested goals to prevent hangs in case there is exponential blowup.

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#### fn stack_coinductive_from( tcx: TyCtxt<'tcx>, stack: &IndexVec<StackDepth, StackEntry<'tcx>>, head: StackDepth ) -> bool

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#### fn tag_cycle_participants( stack: &mut IndexVec<StackDepth, StackEntry<'tcx>>, cycle_participants: &mut FxHashSet<CanonicalInput<'tcx>>, usage_kind: HasBeenUsed, head: StackDepth )

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#### fn clear_dependent_provisional_results( provisional_cache: &mut FxHashMap<CanonicalInput<'tcx>, ProvisionalCacheEntry<'tcx>>, head: StackDepth )

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#### pub(super) fn with_new_goal( &mut self, tcx: TyCtxt<'tcx>, input: CanonicalInput<'tcx>, inspect: &mut ProofTreeBuilder<'tcx>, prove_goal: impl FnMut(&mut Self, &mut ProofTreeBuilder<'tcx>) -> QueryResult<'tcx> ) -> QueryResult<'tcx>

Probably the most involved method of the whole solver.

Given some goal which is proven via the `prove_goal` closure, this handles caching, overflow, and coinductive cycles.

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#### fn response_no_constraints( tcx: TyCtxt<'tcx>, goal: CanonicalInput<'tcx>, certainty: Certainty ) -> QueryResult<'tcx>

## Auto Trait Implementations§

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### impl<'tcx> DynSend for SearchGraph<'tcx>

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### impl<'tcx> DynSync for SearchGraph<'tcx>

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### impl<'tcx> Freeze for SearchGraph<'tcx>

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### impl<'tcx> !RefUnwindSafe for SearchGraph<'tcx>

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### impl<'tcx> Send for SearchGraph<'tcx>

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### impl<'tcx> Sync for SearchGraph<'tcx>

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### impl<'tcx> Unpin for SearchGraph<'tcx>

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### impl<'tcx> !UnwindSafe for SearchGraph<'tcx>

## Blanket Implementations§

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#### const ALIGN: Alignment = _

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#### fn collect_and_apply<I, F>(iter: I, f: F) -> R
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Equivalent to `f(&iter.collect::<Vec<_>>())`.

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#### type Output = R

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#### fn filterable( self, filter_name: &'static str ) -> RequestFilterDataProvider<T, fn(_: DataRequest<'_>) -> bool>

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#### fn into(self) -> U

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### impl<P> IntoQueryParam<P> for P

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#### fn into_query_param(self) -> P

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### impl<T> MaybeResult<T> for T

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#### type Error = !

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#### const ALIGN: usize = _

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### impl<V, T> VZip<V> for T
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#### fn vzip(self) -> V

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### impl<Tcx, T> Value<Tcx> for T
where Tcx: DepContext,

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#### default fn from_cycle_error( tcx: Tcx, cycle_error: &CycleError, _guar: ErrorGuaranteed ) -> T

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## 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: 96 bytes