Top-level declarations

A top-level declaration can appear at the top level or outermost scope of a Unison file. It can be one of the following forms:

• A term declaration, like x = 42
• A type declaration, like
  structural type Optional a

  structural type Optional a
    = lib.base.Optional.Some a
    | lib.base.Optional.None

• A use clause, like use base or use math sqrt