Function match_canonical_var_values 

pub fn match_canonical_var_values<'tcx>(
    tcx: TyCtxt<'tcx>,
    var_kinds: CanonicalVarKinds<'tcx>,
    canonical_ty: Ty<'tcx>,
    inferred_ty: Ty<'tcx>,
) -> Option<CanonicalVarValues<'tcx>>

Structurally pairs a canonicalized type with its inferred type to recover the values rustc replaced with canonical variables. Inference regions are deliberately erased instead.