Reorder erasing/replacing late bound vars and substs

compiler/rustc_typeck/src/check/method/confirm.rs

@@ -462,19 +462,13 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
 
  let sig = self.tcx.fn_sig(def_id);
 
- // Instantiate late-bound regions and substitute the trait
- // parameters into the method type to get the actual method type.
- //
- // N.B., instantiate late-bound regions first so that
- // `instantiate_type_scheme` can normalize associated types that
- // may reference those regions.
- let method_sig = self.replace_bound_vars_with_fresh_vars(sig);
- debug!("late-bound lifetimes from method instantiated, method_sig={:?}", method_sig);
+ let sig = sig.subst(self.tcx, all_substs);
+ debug!("type scheme substituted, sig={:?}", sig);
 
- let method_sig = method_sig.subst(self.tcx, all_substs);
- debug!("type scheme substituted, method_sig={:?}", method_sig);
+ let sig = self.replace_bound_vars_with_fresh_vars(sig);
+ debug!("late-bound lifetimes from method instantiated, sig={:?}", sig);
 
- (method_sig, method_predicates)
+ (sig, method_predicates)
  }
 
  fn add_obligations(

compiler/rustc_typeck/src/check/method/mod.rs

@@ -461,8 +461,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  // `instantiate_type_scheme` can normalize associated types that
  // may reference those regions.
  let fn_sig = tcx.fn_sig(def_id);
- let fn_sig = self.replace_bound_vars_with_fresh_vars(span, infer::FnCall, fn_sig).0;
  let fn_sig = fn_sig.subst(self.tcx, substs);
+ let fn_sig = self.replace_bound_vars_with_fresh_vars(span, infer::FnCall, fn_sig).0;
 
  let InferOk { value, obligations: o } = if is_op {
  self.normalize_op_associated_types_in_as_infer_ok(span, fn_sig, opt_input_expr)

compiler/rustc_typeck/src/check/method/probe.rs

@@ -1784,12 +1784,8 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
  let generics = self.tcx.generics_of(method);
  assert_eq!(substs.len(), generics.parent_count as usize);
 
- // Erase any late-bound regions from the method and substitute
- // in the values from the substitution.
- let xform_fn_sig = self.erase_late_bound_regions(fn_sig);
-
- if generics.params.is_empty() {
- xform_fn_sig.subst(self.tcx, substs)
+ let xform_fn_sig = if generics.params.is_empty() {
+ fn_sig.subst(self.tcx, substs)
  } else {
  let substs = InternalSubsts::for_item(self.tcx, method, |param, _| {
  let i = param.index as usize;
@@ -1807,8 +1803,10 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
  }
  }
  });
- xform_fn_sig.subst(self.tcx, substs)
- }
+ fn_sig.subst(self.tcx, substs)
+ };
+
+ self.erase_late_bound_regions(xform_fn_sig)
  }
 
  /// Gets the type of an impl and generate substitutions with placeholders.