1 use rustc_middle::traits::ObligationCause;
2 use rustc_middle::ty::{self, ToPredicate, Ty};
4 use crate::traits::{Obligation, PredicateObligation};
6 use super::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
9 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
10 /// Instead of normalizing an associated type projection,
11 /// this function generates an inference variable and registers
12 /// an obligation that this inference variable must be the result
13 /// of the given projection. This allows us to proceed with projections
14 /// while they cannot be resolved yet due to missing information or
15 /// simply due to the lack of access to the trait resolution machinery.
16 pub fn infer_projection(
18 param_env: ty::ParamEnv<'tcx>,
19 projection_ty: ty::ProjectionTy<'tcx>,
20 cause: ObligationCause<'tcx>,
21 recursion_depth: usize,
22 obligations: &mut Vec<PredicateObligation<'tcx>>,
24 let def_id = projection_ty.item_def_id;
25 let ty_var = self.next_ty_var(TypeVariableOrigin {
26 kind: TypeVariableOriginKind::NormalizeProjectionType,
27 span: self.tcx.def_span(def_id),
30 ty::Binder::dummy(ty::ProjectionPredicate { projection_ty, term: ty_var.into() });
31 let obligation = Obligation::with_depth(
35 projection.to_predicate(self.tcx),
37 obligations.push(obligation);