type missing_feature =
Features which are not available in all versions of the frontend
Exception thrown by migration functions when a feature is not supported.
val missing_feature_description : missing_feature -> string
missing_feature_description x is a text describing the feature
val missing_feature_minimal_version : missing_feature -> string
missing_feature_minimal_version x is the OCaml version where x was introduced.
val migration_error_message : missing_feature -> string
Turn a missing feature into a reasonable error message.