error:
       … from call site

         at /pwd/lang/eval-fail-function-apply-dollar.nix:6:10:

            5|   add = a: b: a + b;
            6| in add a $ a $ b
             |          ^
            7|

       … while calling 'add'

         at /pwd/lang/eval-fail-function-apply-dollar.nix:5:12:

            4|
            5|   add = a: b: a + b;
             |            ^
            6| in add a $ a $ b

       error: attempt to call something which is not a function but an integer

       at /pwd/lang/eval-fail-function-apply-dollar.nix:6:14:

            5|   add = a: b: a + b;
            6| in add a $ a $ b
             |              ^
            7|