structuredAttrs is enabled

trying https://github.com/yvgude/lean-ctx/archive/refs/tags/v3.9.20.tar.gz
  % Total    % Received % Xferd  Average Speed  Time    Time    Time   Current
                                 Dload  Upload  Total   Spent   Left   Speed

  0      0   0      0   0      0      0      0                              0
  0      0   0      0   0      0      0      0                              0
  0      0   0      0   0      0      0      0                              0

  0      0   0      0   0      0      0      0                              0
100  9.86M   0  9.86M   0      0  8.19M      0           00:01          9.87M
100 17.92M   0 17.92M   0      0  8.41M      0           00:02          9.87M
100 17.92M   0 17.92M   0      0  8.41M      0           00:02          9.87M
100 17.92M   0 17.92M   0      0  8.41M      0           00:02          9.87M
unpacking source archive /nix/var/nix/builds/nix-84735-1580445958/download.tar.gz