Instead of checking for exact bounds, try to prove them

compiler/rustc_infer/src/infer/free_regions.rs

@@ -11,7 +11,7 @@ use rustc_middle::ty::{self, Lift, Region, TyCtxt};
 ///
 /// This stuff is a bit convoluted and should be refactored, but as we
 /// transition to NLL, it'll all go away anyhow.
-pub struct RegionRelations<'a, 'tcx> {
+pub(crate) struct RegionRelations<'a, 'tcx> {
     pub tcx: TyCtxt<'tcx>,
 
     /// The context used for debug messages

compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs

@@ -28,7 +28,7 @@ use std::fmt;
 /// assuming such values can be found. It returns the final values of
 /// all the variables as well as a set of errors that must be reported.
 #[instrument(level = "debug", skip(region_rels, var_infos, data))]
-pub fn resolve<'tcx>(
+pub(crate) fn resolve<'tcx>(
     region_rels: &RegionRelations<'_, 'tcx>,
     var_infos: VarInfos,
     data: RegionConstraintData<'tcx>,