compiler/rustc_error_codes/src/error_codes/E0725.md

   1 A feature attribute named a feature that was disallowed in the compiler
   2 command line flags.
   3
   4 Erroneous code example:
   5
   6 ```ignore (can't specify compiler flags from doctests)
   7 #![feature(never_type)] // error: the feature `never_type` is not in
   8                         // the list of allowed features
   9 ```
  10
  11 Delete the offending feature attribute, or add it to the list of allowed
  12 features in the `-Z allow_features` flag.