[31m[1mERROR[0m[39m: 
  [31m×[0m I don't know how to handle the type returned by `app::c`.
  [31m│[0m
  [31m│[0m     ╭─[[36;1;4msrc/lib.rs[0m:9:1]
  [31m│[0m  [2m 9[0m │     let mut bp = Blueprint::new();
  [31m│[0m  [2m10[0m │     bp.route(GET, "/home", f!(crate::c));
  [31m│[0m     · [35;1m                           ──────┬─────[0m
  [31m│[0m     ·                  [35;1mThe request handler was registered here[0m
  [31m│[0m  [2m11[0m │     bp
  [31m│[0m     ╰────
  [31m│[0m    ╭─[[36;1;4msrc/lib.rs[0m:3:1]
  [31m│[0m  [2m3[0m │ 
  [31m│[0m  [2m4[0m │ pub fn c() -> Box<dyn std::error::Error> {
  [31m│[0m    · [35;1m              ─────────────┬────────────[0m
  [31m│[0m    ·                            [35;1m╰── The output type that I can't handle[0m
  [31m│[0m  [2m5[0m │     todo!()
  [31m│[0m    ╰────