[31m[1mERROR[0m[39m: 
  [31m×[0m I can't generate code that will pass the borrow checker *and* match the
  [31m│[0m instructions in your blueprint:
  [31m│[0m - `app::handler` wants to borrow `pavex::request::RequestHead`
  [31m│[0m - but `app::b`, which is invoked earlier on, consumes
  [31m│[0m `pavex::request::RequestHead` by value
  [31m│[0m 
  [31m│[0m Since I'm not allowed to clone `pavex::request::RequestHead`, I can't
  [31m│[0m resolve this conflict.
  [31m│[0m
  [31m│[0m   [36mhelp:[0m Consider changing the signature of `app::b`.
  [31m│[0m         It takes `pavex::request::RequestHead` by value. Would a shared
  [31m│[0m         reference, `&pavex::request::RequestHead`, be enough?