1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
use rustc::traits::{EvaluationResult, Obligation, ObligationCause,
OverflowError, SelectionContext, TraitQueryMode};
use rustc::traits::query::CanonicalPredicateGoal;
use rustc::ty::query::Providers;
use rustc::ty::{ParamEnvAnd, TyCtxt};
use syntax::codemap::DUMMY_SP;
crate fn provide(p: &mut Providers) {
*p = Providers {
evaluate_obligation,
..*p
};
}
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)
})
}