# Module Migrate_parsetree_406_405_migrate.Def

    module Def: Migrate_parsetree_def

    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`

    exception Migration_error of missing_feature * Location.t

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 `x`.

    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.