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use rustc::traits::{EvaluationResult, Obligation, ObligationCause,
OverflowError, SelectionContext, TraitQueryMode};
use rustc::traits::query::CanonicalPredicateGoal;
use rustc::ty::{ParamEnvAnd, TyCtxt};
use syntax::codemap::DUMMY_SP;
crate fn evaluate_obligation<'tcx>(
tcx: TyCtxt<'_, 'tcx, 'tcx>,
goal: CanonicalPredicateGoal<'tcx>,
) -> Result<EvaluationResult, OverflowError> {
tcx.infer_ctxt().enter(|ref infcx| {
let (
ParamEnvAnd {
param_env,
value: predicate,
},
_canonical_inference_vars,
) = infcx.instantiate_canonical_with_fresh_inference_vars(DUMMY_SP, &goal);
let mut selcx = SelectionContext::with_query_mode(&infcx, TraitQueryMode::Canonical);
let obligation = Obligation::new(ObligationCause::dummy(), param_env, predicate);
selcx.evaluate_obligation_recursively(&obligation)
})
}