error:
       … while evaluating the attribute 'set'
         at /pwd/lang/eval-fail-dup-dynamic-attrs.nix:2:3:
            1| {
            2|   set = {
             |   ^
            3|     "${"" + "b"}" = 1;

       error: dynamic attribute 'b' already defined at /pwd/lang/eval-fail-dup-dynamic-attrs.nix:3:5
       at /pwd/lang/eval-fail-dup-dynamic-attrs.nix:6:5:
            5|   set = {
            6|     "${"b" + ""}" = 2;
             |     ^
            7|   };