# Trait rustc_infer::traits::TraitEngine

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    pub trait TraitEngine<'tcx>: 'tcx {
        // Required methods
        fn register_predicate_obligation(
            &mut self,
            infcx: &InferCtxt<'tcx>,
            obligation: PredicateObligation<'tcx>
        );
        fn select_where_possible(
            &mut self,
            infcx: &InferCtxt<'tcx>
        ) -> Vec<FulfillmentError<'tcx>>;
        fn collect_remaining_errors(
            &mut self,
            infcx: &InferCtxt<'tcx>
        ) -> Vec<FulfillmentError<'tcx>>;
        fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>>;
        fn drain_unstalled_obligations(
            &mut self,
            infcx: &InferCtxt<'tcx>
        ) -> Vec<PredicateObligation<'tcx>>;

        // Provided method
        fn register_bound(
            &mut self,
            infcx: &InferCtxt<'tcx>,
            param_env: ParamEnv<'tcx>,
            ty: Ty<'tcx>,
            def_id: DefId,
            cause: ObligationCause<'tcx>
        ) { ... }
    }

## Required Methods§

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#### fn register_predicate_obligation( &mut self, infcx: &InferCtxt<'tcx>, obligation: PredicateObligation<'tcx> )

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#### fn select_where_possible( &mut self, infcx: &InferCtxt<'tcx> ) -> Vec<FulfillmentError<'tcx>>

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#### fn collect_remaining_errors( &mut self, infcx: &InferCtxt<'tcx> ) -> Vec<FulfillmentError<'tcx>>

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#### fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>>

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#### fn drain_unstalled_obligations( &mut self, infcx: &InferCtxt<'tcx> ) -> Vec<PredicateObligation<'tcx>>

Among all pending obligations, collect those are stalled on a inference variable which has changed since the last call to `select_where_possible`. Those obligations are marked as successful and returned.

## Provided Methods§

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#### fn register_bound( &mut self, infcx: &InferCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>, def_id: DefId, cause: ObligationCause<'tcx> )

Requires that `ty` must implement the trait with `def_id` in the given environment. This trait must not have any type parameters (except for `Self`).

## Implementors§