type missing_feature = | Pexp_letexception| Ppat_open| Pexp_unreachable| PSig| Pcstr_record| Pconst_integer| Pconst_float| Pcl_open| Pcty_open| Oinherit| Pwith_typesubst_longident| Pwith_modsubst_longident| Pexp_open| Pexp_letop| Psig_typesubst| Psig_modsubst| Otyp_module| Immediate64| Anonymous_let_module| Anonymous_unpack| Anonymous_module_binding| Anonymous_module_declaration| ExistentialsInPatternMatching| With_modtype| With_modtypesubst| Psig_modtypesubstFeatures which are not available in all versions of the frontend
exception Migration_error of missing_feature * Location.tException thrown by migration functions when a feature is not supported.
val missing_feature_description : missing_feature -> stringmissing_feature_description x is a text describing the feature x.
val missing_feature_minimal_version : missing_feature -> stringmissing_feature_minimal_version x is the OCaml version where x was introduced.
val migration_error_message : missing_feature -> stringTurn a missing feature into a reasonable error message.