---
expr_app := expr_app expr_select
  expr_app := expr_app expr_select
    ID := "ID"
      ID "import" (1, 1)
    SPATH := "SPATH"
      SPATH "<nixpkgs>" (1, 8)
  expr_simple := { binds }
    { := "{"
      { "{" (1, 18)
    binds := 
    } := "}"
      } "}" (1, 19)