{-
************************************************************************
*                                                                      *
                Implicit TyThings
*                                                                      *
************************************************************************

Note [Implicit TyThings]
~~~~~~~~~~~~~~~~~~~~~~~~
  DEFINITION: An "implicit" TyThing is one that does not have its own
  IfaceDecl in an interface file.  Instead, its binding in the type
  environment is created as part of typechecking the IfaceDecl for
  some other thing.

Examples:
  * All DataCons are implicit, because they are generated from the
    IfaceDecl for the data/newtype.  Ditto class methods.

  * Record selectors are *not* implicit, because they get their own
    free-standing IfaceDecl.

  * Associated data/type families are implicit because they are
    included in the IfaceDecl of the parent class.  (NB: the
    IfaceClass decl happens to use IfaceDecl recursively for the
    associated types, but that's irrelevant here.)

  * Dictionary function Ids are not implicit.

  * Axioms for newtypes are implicit (same as above), but axioms
    for data/type family instances are *not* implicit (like DFunIds).
-}

-- | Determine the 'TyThing's brought into scope by another 'TyThing'
-- /other/ than itself. For example, Id's don't have any implicit TyThings
-- as they just bring themselves into scope, but classes bring their
-- dictionary datatype, type constructor and some selector functions into
-- scope, just for a start!

-- N.B. the set of TyThings returned here *must* match the set of
-- names returned by LoadIface.ifaceDeclImplicitBndrs, in the sense that
-- TyThing.getOccName should define a bijection between the two lists.
-- This invariant is used in LoadIface.loadDecl (see note [Tricky iface loop])
-- The order of the list does not matter.
implicitTyThings :: TyThing -> [TyThing]
implicitTyThings (AnId _)       = []
implicitTyThings :: TyThing -> [TyThing]
implicitTyThings (AnId _)       = []
implicitTyThings (AnId _)       = []