error:
       … in the right operand of the update (//) operator
         at /pwd/lang/eval-fail-recursion.nix:1:12:
            1| let a = {} // a; in a.foo
             |            ^
            2|

       error: infinite recursion encountered
       at /pwd/lang/eval-fail-recursion.nix:1:15:
            1| let a = {} // a; in a.foo
             |               ^
            2|