mkTupleCase :: UniqSupply       -- ^ For inventing names of intermediate variables
            -> [Id]             -- ^ The tuple identifiers to pattern match on
            -> CoreExpr         -- ^ Body of the case
            -> Id               -- ^ A variable of the same type as the scrutinee
            -> CoreExpr         -- ^ Scrutinee
            -> CoreExpr
-- ToDo: eliminate cases where none of the variables are needed.
--
--         mkTupleCase uniqs [a,b,c,d] body v e
--           = case e of v { (p,q) ->
--             case p of p { (a,b) ->
--             case q of q { (c,d) ->
--             body }}}
mkTupleCase uniqs vars body scrut_var scrut
  = mk_tuple_case uniqs (chunkify vars) body
  where
    -- This is the case where don't need any nesting
    mk_tuple_case _ [vars] body
      = mkSmallTupleCase vars body scrut_var scrut

    -- This is the case where we must make nest tuples at least once
    mk_tuple_case us vars_s body
      = let (us', vars', body') = foldr one_tuple_case (us, [], body) vars_s
            in mk_tuple_case us' (chunkify vars') body'

    one_tuple_case chunk_vars (us, vs, body)
      = let (uniq, us') = takeUniqFromSupply us
            scrut_var = mkSysLocal (fsLit "ds") uniq
              (mkBoxedTupleTy (map idType chunk_vars))
            body' = mkSmallTupleCase chunk_vars body scrut_var (Var scrut_var)
        in (us', scrut_var:vs, body')

-- | As 'mkTupleCase', but for a tuple that is small enough to be guaranteed
-- not to need nesting.
mkTupleCase :: UniqSupply       -- ^ For inventing names of intermediate variables
            -> [Id]             -- ^ The tuple identifiers to pattern match on
            -> CoreExpr         -- ^ Body of the case
            -> Id               -- ^ A variable of the same type as the scrutinee
            -> CoreExpr         -- ^ Scrutinee
            -> CoreExpr
mkTupleCase uniqs vars body scrut_var scrut
  = mk_tuple_case uniqs (chunkify vars) body
  where
    -- This is the case where don't need any nesting
    mk_tuple_case _ [vars] body
      = mkSmallTupleCase vars body scrut_var scrut

    -- This is the case where we must make nest tuples at least once
    mk_tuple_case us vars_s body
      = let (us', vars', body') = foldr one_tuple_case (us, [], body) vars_s
            in mk_tuple_case us' (chunkify vars') body'

    one_tuple_case chunk_vars (us, vs, body)
      = let (uniq, us') = takeUniqFromSupply us
            scrut_var = mkSysLocal (fsLit "ds") uniq
              (mkBoxedTupleTy (map idType chunk_vars))
            body' = mkSmallTupleCase chunk_vars body scrut_var (Var scrut_var)
        in (us', scrut_var:vs, body')

-- | As 'mkTupleCase', but for a tuple that is small enough to be guaranteed
-- not to need nesting.
mkTupleCase uniqs vars body scrut_var scrut
  = mk_tuple_case uniqs (chunkify vars) body
  where
    -- This is the case where don't need any nesting
    mk_tuple_case _ [vars] body
      = mkSmallTupleCase vars body scrut_var scrut

    -- This is the case where we must make nest tuples at least once
    mk_tuple_case us vars_s body
      = let (us', vars', body') = foldr one_tuple_case (us, [], body) vars_s
            in mk_tuple_case us' (chunkify vars') body'

    one_tuple_case chunk_vars (us, vs, body)
      = let (uniq, us') = takeUniqFromSupply us
            scrut_var = mkSysLocal (fsLit "ds") uniq
              (mkBoxedTupleTy (map idType chunk_vars))
            body' = mkSmallTupleCase chunk_vars body scrut_var (Var scrut_var)
        in (us', scrut_var:vs, body')

-- | As 'mkTupleCase', but for a tuple that is small enough to be guaranteed
-- not to need nesting.