#12977: Template Haskell: unboxedTupleTypeName doesn't handle unboxed 0- and 1-tuples -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: RyanGlScott Type: bug | Status: new Priority: normal | Milestone: Component: Template | Version: 8.0.1 Haskell | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC has a notion of unboxed 0-tuples and 1-tuples: {{{ λ> :set -XUnboxedTuples λ> :k (##) (##) :: TYPE 'GHC.Types.VoidRep λ> :k (# Int #) (# Int #) :: TYPE 'GHC.Types.UnboxedTupleRep }}} But it is impossible to acquire the `Name`s of these type constructors using `unboxedTupleTypeName` from `template-haskell`: {{{ λ> :set -XTemplateHaskell λ> :m + Language.Haskell.TH Language.Haskell.TH.Syntax λ> :k $(conT (unboxedTupleTypeName 0)) <interactive>:1:1: error: • Exception when trying to run compile-time code: unboxedTupleTypeName 0 CallStack (from HasCallStack): error, called at libraries/template- haskell/Language/Haskell/TH/Syntax.hs:1179:26 in template- haskell:Language.Haskell.TH.Syntax Code: conT (unboxedTupleTypeName 0) • In the untyped splice: $(conT (unboxedTupleTypeName 0)) λ> :k $(conT (unboxedTupleTypeName 1)) <interactive>:1:1: error: • Exception when trying to run compile-time code: unboxedTupleTypeName 1 CallStack (from HasCallStack): error, called at libraries/template- haskell/Language/Haskell/TH/Syntax.hs:1180:26 in template- haskell:Language.Haskell.TH.Syntax Code: conT (unboxedTupleTypeName 1) • In the untyped splice: $(conT (unboxedTupleTypeName 1)) }}} And similarly for `unboxedTupleDataName`. This is because of [http://git.haskell.org/ghc.git/blob/9c9a2229fe741c55a8fb8d0c6380ec066a77722b... /template-haskell/Language/Haskell/TH/Syntax.hs#l1184 silly restrictions] put in place on the definitions of `unboxedTupleTypeName` and `unboxedTupleDataName` within `template-haskell`: {{{#!hs -- Unboxed tuple data and type constructors -- | Unboxed tuple data constructor unboxedTupleDataName :: Int -> Name -- | Unboxed tuple type constructor unboxedTupleTypeName :: Int -> Name unboxedTupleDataName 0 = error "unboxedTupleDataName 0" unboxedTupleDataName 1 = error "unboxedTupleDataName 1" unboxedTupleDataName n = mk_unboxed_tup_name (n-1) DataName unboxedTupleTypeName 0 = error "unboxedTupleTypeName 0" unboxedTupleTypeName 1 = error "unboxedTupleTypeName 1" unboxedTupleTypeName n = mk_unboxed_tup_name (n-1) TcClsName }}} It should be possible to lift this restriction. I'll work on this. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12977 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler