#13549: GHC 8.2.1's typechecker rejects code generated by singletons that 8.0 accepts -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I recently attempted to upgrade `singletons` to use GHC 8.2.1, but was thwarted when GHC's typechecker rejected code that was generated by Template Haskell. I was able to put all of this code in a single module (which I've attached), but sadly, it's 1367 lines long. What's important is that GHC 8.0.1 and 8.0.2 accept this code, but neither 8.2.1-rc1 nor HEAD do. Here is the error message you get, in its full glory: {{{ $ /opt/ghc/8.2.1/bin/ghci Bug.hs GHCi, version 8.2.0.20170403: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Bug.hs:1328:59: error: • Couldn't match type ‘c69895866216793215480’ with ‘[a_a337f]’ ‘c69895866216793215480’ is untouchable inside the constraints: (arg_a33hh ~ xs_a33fp, arg_a33hi ~ r_a33fq) bound by the type signature for: lambda_a33iH :: forall (xs_a33fp :: [a_a337f]) (r_a33fq :: [[a_a337f]]). (arg_a33hh ~ xs_a33fp, arg_a33hi ~ r_a33fq) => Sing xs_a33fp -> Sing r_a33fq -> Sing (Apply (Apply (Let6989586621679736980InterleaveSym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO) arg_a33hh) arg_a33hi) at Bug.hs:(1289,35)-(1294,157) Expected type: Sing t -> Sing t1 -> Sing t2 -> Sing (((Let6989586621679736980Interleave'Sym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO @@ t) @@ t1) @@ t2) Actual type: Sing t -> Sing t1 -> Sing t2 -> Sing (Apply (Apply (Apply (Let6989586621679736980Interleave'Sym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO) t) t1) t2) • In the second argument of ‘singFun3’, namely ‘sInterleave'’ In the first argument of ‘applySing’, namely ‘((singFun3 (Proxy :: Proxy (Let6989586621679736980Interleave'Sym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO))) sInterleave')’ In the first argument of ‘applySing’, namely ‘((applySing ((singFun3 (Proxy :: Proxy (Let6989586621679736980Interleave'Sym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO))) sInterleave')) ((singFun1 (Proxy :: Proxy IdSym0)) sId))’ • Relevant bindings include sX_6989586621679737266 :: Sing (Let6989586621679737265X_6989586621679737266Sym6 xs0_a33a0 t_a33aL ts_a33aM is_a33aO xs_a33fp r_a33fq) (bound at Bug.hs:1321:41) r_a33iK :: Sing r_a33fq (bound at Bug.hs:1295:57) xs_a33iJ :: Sing xs_a33fp (bound at Bug.hs:1295:48) lambda_a33iH :: Sing xs_a33fp -> Sing r_a33fq -> Sing (Apply (Apply (Let6989586621679736980InterleaveSym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO) arg_a33hh) arg_a33hi) (bound at Bug.hs:1295:35) sR :: Sing arg_a33hi (bound at Bug.hs:1287:45) sXs :: Sing arg_a33hh (bound at Bug.hs:1287:41) sInterleave' :: forall (arg_a33he :: TyFun [a_a337f] c69895866216793215480 -> *) (arg_a33hf :: [a_a337f]) (arg_a33hg :: [c69895866216793215480]). Sing arg_a33he -> Sing arg_a33hf -> Sing arg_a33hg -> Sing (Apply (Apply (Apply (Let6989586621679736980Interleave'Sym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO) arg_a33he) arg_a33hf) arg_a33hg) (bound at Bug.hs:1166:29) lambda_a33ha :: Sing t_a33aL -> Sing ts_a33aM -> Sing is_a33aO -> Sing (Apply (Apply (Let6989586621679736931PermsSym1 xs0_a33a0) arg_a33h0) arg_a33h1) (bound at Bug.hs:1153:23) sTs :: Sing n_a1kQd (bound at Bug.hs:1143:34) sT :: Sing n_a1kQc (bound at Bug.hs:1143:31) lambda_a33gY :: Sing xs0_a33a0 -> Sing (Apply PermutationsSym0 t_a33gX) (bound at Bug.hs:1127:11) (Some bindings suppressed; use -fmax-relevant-binds=N or -fno-max- relevant-binds) | 1328 | sInterleave')) | ^^^^^^^^^^^^ Bug.hs:1328:59: error: • Could not deduce: Let6989586621679736980Interleave' xs0_a33a0 t_a33aL ts_a33aM is_a33aO t t1 t2 ~ Let6989586621679736980Interleave' xs0_a33a0 t_a33aL ts_a33aM is_a33aO t t1 t2 from the context: t_a33gX ~ xs0_a33a0 bound by the type signature for: lambda_a33gY :: forall (xs0_a33a0 :: [a_a337f]). t_a33gX ~ xs0_a33a0 => Sing xs0_a33a0 -> Sing (Apply PermutationsSym0 t_a33gX) at Bug.hs:(1122,11)-(1126,67) or from: arg_a33h0 ~ (n_a1kQc : n_a1kQd) bound by a pattern with constructor: SCons :: forall a_11 (z_a1kQb :: [a_11]) (n_a1kQc :: a_11) (n_a1kQd :: [a_11]). z_a1kQb ~ (n_a1kQc : n_a1kQd) => Sing n_a1kQc -> Sing n_a1kQd -> Sing z_a1kQb, in an equation for ‘sPerms’ at Bug.hs:1143:25-36 or from: (arg_a33h0 ~ Apply (Apply (:$) t_a33aL) ts_a33aM, arg_a33h1 ~ is_a33aO) bound by the type signature for: lambda_a33ha :: forall (t_a33aL :: a_a337f) (ts_a33aM :: [a_a337f]) (is_a33aO :: [a_a337f]). (arg_a33h0 ~ Apply (Apply (:$) t_a33aL) ts_a33aM, arg_a33h1 ~ is_a33aO) => Sing t_a33aL -> Sing ts_a33aM -> Sing is_a33aO -> Sing (Apply (Apply (Let6989586621679736931PermsSym1 xs0_a33a0) arg_a33h0) arg_a33h1) at Bug.hs:(1145,23)-(1152,117) or from: (arg_a33hh ~ xs_a33fp, arg_a33hi ~ r_a33fq) bound by the type signature for: lambda_a33iH :: forall (xs_a33fp :: [a_a337f]) (r_a33fq :: [[a_a337f]]). (arg_a33hh ~ xs_a33fp, arg_a33hi ~ r_a33fq) => Sing xs_a33fp -> Sing r_a33fq -> Sing (Apply (Apply (Let6989586621679736980InterleaveSym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO) arg_a33hh) arg_a33hi) at Bug.hs:(1289,35)-(1294,157) Expected type: Sing t -> Sing t1 -> Sing t2 -> Sing (((Let6989586621679736980Interleave'Sym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO @@ t) @@ t1) @@ t2) Actual type: Sing t -> Sing t1 -> Sing t2 -> Sing (Apply (Apply (Apply (Let6989586621679736980Interleave'Sym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO) t) t1) t2) The type variable ‘c69895866216793215480’ is ambiguous Use -fprint-explicit-kinds to see the kind arguments • In the second argument of ‘singFun3’, namely ‘sInterleave'’ In the first argument of ‘applySing’, namely ‘((singFun3 (Proxy :: Proxy (Let6989586621679736980Interleave'Sym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO))) sInterleave')’ In the first argument of ‘applySing’, namely ‘((applySing ((singFun3 (Proxy :: Proxy (Let6989586621679736980Interleave'Sym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO))) sInterleave')) ((singFun1 (Proxy :: Proxy IdSym0)) sId))’ • Relevant bindings include sX_6989586621679737266 :: Sing (Let6989586621679737265X_6989586621679737266Sym6 xs0_a33a0 t_a33aL ts_a33aM is_a33aO xs_a33fp r_a33fq) (bound at Bug.hs:1321:41) r_a33iK :: Sing r_a33fq (bound at Bug.hs:1295:57) xs_a33iJ :: Sing xs_a33fp (bound at Bug.hs:1295:48) lambda_a33iH :: Sing xs_a33fp -> Sing r_a33fq -> Sing (Apply (Apply (Let6989586621679736980InterleaveSym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO) arg_a33hh) arg_a33hi) (bound at Bug.hs:1295:35) sR :: Sing arg_a33hi (bound at Bug.hs:1287:45) sXs :: Sing arg_a33hh (bound at Bug.hs:1287:41) sInterleave' :: forall (arg_a33he :: TyFun [a_a337f] c69895866216793215480 -> *) (arg_a33hf :: [a_a337f]) (arg_a33hg :: [c69895866216793215480]). Sing arg_a33he -> Sing arg_a33hf -> Sing arg_a33hg -> Sing (Apply (Apply (Apply (Let6989586621679736980Interleave'Sym4 xs0_a33a0 t_a33aL ts_a33aM is_a33aO) arg_a33he) arg_a33hf) arg_a33hg) (bound at Bug.hs:1166:29) lambda_a33ha :: Sing t_a33aL -> Sing ts_a33aM -> Sing is_a33aO -> Sing (Apply (Apply (Let6989586621679736931PermsSym1 xs0_a33a0) arg_a33h0) arg_a33h1) (bound at Bug.hs:1153:23) sTs :: Sing n_a1kQd (bound at Bug.hs:1143:34) sT :: Sing n_a1kQc (bound at Bug.hs:1143:31) lambda_a33gY :: Sing xs0_a33a0 -> Sing (Apply PermutationsSym0 t_a33gX) (bound at Bug.hs:1127:11) (Some bindings suppressed; use -fmax-relevant-binds=N or -fno-max- relevant-binds) | 1328 | sInterleave')) | ^^^^^^^^^^^^ }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13549 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler