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use infer::InferCtxt;
use smallvec::SmallVec;
use traits::{EvaluationResult, PredicateObligation, SelectionContext,
TraitQueryMode, OverflowError};
impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
pub fn predicate_may_hold(
&self,
obligation: &PredicateObligation<'tcx>,
) -> bool {
self.evaluate_obligation(obligation).may_apply()
}
pub fn predicate_must_hold(
&self,
obligation: &PredicateObligation<'tcx>,
) -> bool {
self.evaluate_obligation(obligation) == EvaluationResult::EvaluatedToOk
}
fn evaluate_obligation(
&self,
obligation: &PredicateObligation<'tcx>,
) -> EvaluationResult {
let mut _orig_values = SmallVec::new();
let c_pred = self.canonicalize_query(&obligation.param_env.and(obligation.predicate),
&mut _orig_values);
match self.tcx.global_tcx().evaluate_obligation(c_pred) {
Ok(result) => result,
Err(OverflowError) => {
let mut selcx =
SelectionContext::with_query_mode(&self, TraitQueryMode::Standard);
selcx.evaluate_obligation_recursively(obligation)
.expect("Overflow should be caught earlier in standard query mode")
}
}
}
}