ibc i (IBCMetavar n) f =
     case lookup n (idris_metavars i) of
          Nothing -> return f
          Just t -> return f { ibc_metavars = (n, t) : ibc_metavars f }
ibc i (IBCMetavar n) f =
     case lookup n (idris_metavars i) of
          Nothing -> return f
          Just t -> return f { ibc_metavars = (n, t) : ibc_metavars f }
ibc i (IBCMetavar n) f =
     case lookup n (idris_metavars i) of
          Nothing -> return f
          Just t -> return f { ibc_metavars = (n, t) : ibc_metavars f }