Remove lower_arg_ty as all callers were passing None

compiler/rustc_hir_analysis/src/collect.rs

@@ -494,7 +494,7 @@ impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> {
 
                 // Only visit the type looking for `_` if we didn't fix the type above
                 visitor.visit_ty_unambig(a);
-                self.lowerer().lower_arg_ty(a, None)
+                self.lowerer().lower_ty(a)
             })
             .collect();
 

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -2708,16 +2708,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
     }
 
-    pub fn lower_arg_ty(&self, ty: &hir::Ty<'tcx>, expected_ty: Option<Ty<'tcx>>) -> Ty<'tcx> {
-        match ty.kind {
-            hir::TyKind::Infer(()) if let Some(expected_ty) = expected_ty => {
-                self.record_ty(ty.hir_id, expected_ty, ty.span);
-                expected_ty
-            }
-            _ => self.lower_ty(ty),
-        }
-    }
-
     /// Lower a function type from the HIR to our internal notion of a function signature.
     #[instrument(level = "debug", skip(self, hir_id, safety, abi, decl, generics, hir_ty), ret)]
     pub fn lower_fn_ty(