{"ast_node_type":"other","tokens":[{"end":136,"kind":"keyword","start":0,"text":"Fn,"}]}
    Fn,                      kw::Fn,                   fn_trait,                   Target::Trait,          GenericRequirement::Exact(1);
    FnMut,                   sym::fn_mut,              fn_mut_trait,               Target::Trait,          GenericRequirement::Exact(1);