pub trait InferCtxtExt<'tcx> {
// Required methods
fn predicate_may_hold(&self, obligation: &PredicateObligation<'tcx>) -> bool;
fn predicate_must_hold_considering_regions(
&self,
obligation: &PredicateObligation<'tcx>,
) -> bool;
fn predicate_must_hold_modulo_regions(
&self,
obligation: &PredicateObligation<'tcx>,
) -> bool;
fn evaluate_obligation(
&self,
obligation: &PredicateObligation<'tcx>,
) -> Result<EvaluationResult, OverflowError>;
fn evaluate_obligation_no_overflow(
&self,
obligation: &PredicateObligation<'tcx>,
) -> EvaluationResult;
}
Required Methods§
sourcefn predicate_may_hold(&self, obligation: &PredicateObligation<'tcx>) -> bool
fn predicate_may_hold(&self, obligation: &PredicateObligation<'tcx>) -> bool
Evaluates whether the predicate can be satisfied (by any means)
in the given ParamEnv
.
sourcefn predicate_must_hold_considering_regions(
&self,
obligation: &PredicateObligation<'tcx>,
) -> bool
fn predicate_must_hold_considering_regions( &self, obligation: &PredicateObligation<'tcx>, ) -> bool
Evaluates whether the predicate can be satisfied in the given
ParamEnv
, and returns false
if not certain. However, this is
not entirely accurate if inference variables are involved.
This version may conservatively fail when outlives obligations
are required. Therefore, this version should only be used for
optimizations or diagnostics and be treated as if it can always
return false
.
§Example
trait Trait {}
fn check<T: Trait>() {}
fn foo<T: 'static>()
where
&'static T: Trait,
{
// Evaluating `&'?0 T: Trait` adds a `'?0: 'static` outlives obligation,
// which means that `predicate_must_hold_considering_regions` will return
// `false`.
check::<&'_ T>();
}
sourcefn predicate_must_hold_modulo_regions(
&self,
obligation: &PredicateObligation<'tcx>,
) -> bool
fn predicate_must_hold_modulo_regions( &self, obligation: &PredicateObligation<'tcx>, ) -> bool
Evaluates whether the predicate can be satisfied in the given
ParamEnv
, and returns false
if not certain. However, this is
not entirely accurate if inference variables are involved.
This version ignores all outlives constraints.
sourcefn evaluate_obligation(
&self,
obligation: &PredicateObligation<'tcx>,
) -> Result<EvaluationResult, OverflowError>
fn evaluate_obligation( &self, obligation: &PredicateObligation<'tcx>, ) -> Result<EvaluationResult, OverflowError>
Evaluate a given predicate, capturing overflow and propagating it back.
sourcefn evaluate_obligation_no_overflow(
&self,
obligation: &PredicateObligation<'tcx>,
) -> EvaluationResult
fn evaluate_obligation_no_overflow( &self, obligation: &PredicateObligation<'tcx>, ) -> EvaluationResult
Helper function that canonicalizes and runs the query. If an overflow results, we re-run it in the local context so we can report a nice error.