environment, mapping meta field identifiers to static FDD fields, and, for convenience, the initializer and mutability of the identifier
type t
val empty : t
exception
Full
val add : t ‑> string ‑> Syntax.meta_init ‑> bool ‑> t
may raise Full
val lookup : t ‑> string ‑> field * (Syntax.meta_init * bool)
may raise Not_found