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
|
use rustc_middle::traits::ObligationCause;
use rustc_middle::ty::{self, ToPredicate, Ty};
use crate::traits::{Obligation, PredicateObligation};
use super::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use super::InferCtxt;
impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
/// Instead of normalizing an associated type projection,
/// this function generates an inference variable and registers
/// an obligation that this inference variable must be the result
/// of the given projection. This allows us to proceed with projections
/// while they cannot be resolved yet due to missing information or
/// simply due to the lack of access to the trait resolution machinery.
pub fn infer_projection(
&self,
param_env: ty::ParamEnv<'tcx>,
projection_ty: ty::ProjectionTy<'tcx>,
cause: ObligationCause<'tcx>,
recursion_depth: usize,
obligations: &mut Vec<PredicateObligation<'tcx>>,
) -> Ty<'tcx> {
let def_id = projection_ty.item_def_id;
let ty_var = self.next_ty_var(TypeVariableOrigin {
kind: TypeVariableOriginKind::NormalizeProjectionType,
span: self.tcx.def_span(def_id),
});
let projection =
ty::Binder::dummy(ty::ProjectionPredicate { projection_ty, term: ty_var.into() });
let obligation = Obligation::with_depth(
cause,
recursion_depth,
param_env,
projection.to_predicate(self.tcx),
);
obligations.push(obligation);
ty_var
}
}
|
