[GHC] #10796: Illegal data constructor name: `fromList' ... When splicing a TH expression
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression -------------------------------------+------------------------------------- Reporter: erisco | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Template | Version: 7.8.3 Haskell | Keywords: | Operating System: Windows Architecture: x86_64 | Type of failure: None/Unknown (amd64) | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- At the end is a log of my ghci session reproducing the issue. It is expected that the splice should succeed, but GHC complains "Illegal data constructor name: `fromList' ... When splicing a TH expression". Full definitions being used can be found at http://hackage.haskell.org/package/regex-tdfa-quasiquoter-0.2.0.0 . Briefly, this is the splice being used. {{{#!hs [e|patternToRegex $patternExp $compOptsExp $execOptsExp|] where patternExp = dataToExpQ (const Nothing) pattern compOptsExp = dataToExpQ (const Nothing) compOpts execOptsExp = dataToExpQ (const Nothing) execOpts }}} Data and Typeable instances are derived (using -XStandaloneDeriving -XDeriveDataTypeable) as orphan instances in the Internal module. The issue occurs when using bracket expressions (in POSIX regular expressions). There may be other cases but I have not uncovered them. {{{
ghci GHCi, version 7.8.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done.
:set -XQuasiQuotes import Text.Regex.TDFA.QuasiQuoter :t [re|;[a]|] Loading package transformers-0.3.0.0 ... linking ... done. Loading package array-0.5.0.0 ... linking ... done. Loading package deepseq-1.3.0.2 ... linking ... done. Loading package bytestring-0.10.4.0 ... linking ... done. Loading package containers-0.5.5.1 ... linking ... done. Loading package mtl-2.1.3.1 ... linking ... done. Loading package regex-base-0.93.2 ... linking ... done. Loading package text-1.2.0.3 ... linking ... done. Loading package parsec-3.1.9 ... linking ... done. Loading package regex-tdfa-1.2.0 ... linking ... done. Loading package pretty-1.1.1.1 ... linking ... done. Loading package template-haskell ... linking ... done. Loading package regex-tdfa-quasiquoter-0.2.0.0 ... linking ... done.
<interactive>:1:5: Illegal data constructor name: `fromList' When splicing a TH expression: Text.Regex.TDFA.TDFA.patternToRegex (GHC.Tuple.(,) (Text.Regex.TDFA.Pattern.POr ((GHC.Types.:) (Text.Regex.TDFA.Pattern.PConcat ((GHC.Types.:) (Text.Regex.TDFA.Pattern.PAny (Text.Regex.TDFA.Common.DoPa 1) (Text.Regex.TDFA.Pattern.PatternSet (Data.Maybe.Just (Data.Set.Base.fromList ((GHC.Types.:) 'a' GHC.Types.[]))) Data.Maybe.Nothing Data.Maybe.Nothing Data.Maybe.Nothing)) GHC.Types.[])) GHC.Types.[])) (GHC.Tuple.(,) 0 (Text.Regex.TDFA.Common.DoPa 1))) (Text.Regex.TDFA.Common.CompOption GHC.Types.True GHC.Types.True GHC.Types.True GHC.Types.True GHC.Types.False) (Text.Regex.TDFA.Common.ExecOption GHC.Types.True)
}}}
-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10796 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression -------------------------------------+------------------------------------- Reporter: erisco | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Template Haskell | Version: 7.8.3 Resolution: | Keywords: Operating System: Windows | Architecture: x86_64 | (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by simonpj): This could be the `regex-tdfa-quasiquoter` package generating illegal Haskell, no? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10796#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression -------------------------------------+------------------------------------- Reporter: erisco | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Template Haskell | Version: 7.8.3 Resolution: | Keywords: Operating System: Windows | Architecture: x86_64 | (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by goldfire): A little poking through shows me that this is an infelicity in the containers library. The splice above calls `Language.Haskell.TH.Quote.dataToQa`, which performs lifting (in the sense of TH's `lift` operation and `Lift` class) based on a `Data` instance. The data involved includes a `Data.Set.Set`. And `Set`'s `Data` instance reads, in part {{{ instance (Data a, Ord a) => Data (Set a) where toConstr _ = fromListConstr fromListConstr :: Constr fromListConstr = mkConstr setDataType "fromList" [] Prefix }}} Note that the "constructor" is named `fromList`. But this is a lie, of course. It's done to preserve abstraction, which is a laudable goal, so I'm not calling it a bug. An easy solution here would be to generalize `dataToQa` to check if it's given a data constructor or just a function and react accordingly. It really should be getting a constructor, but there seems to be no harm in allowing `Data` instances to lie like this and continue gracefully. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10796#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression -------------------------------------+------------------------------------- Reporter: erisco | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Template Haskell | Version: 7.8.3 Resolution: | Keywords: newcomer Operating System: Windows | Architecture: x86_64 | (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by goldfire): * keywords: => newcomer * milestone: => 7.12.1 Comment: Milestoning this so that I return to it when dispatching a bunch of TH tickets this fall. But this would be easy for just about anyone to tackle. Just update `dataToQa`! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10796#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression -------------------------------------+------------------------------------- Reporter: erisco | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Template Haskell | Version: 7.8.3 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by thomie): * os: Windows => Unknown/Multiple * architecture: x86_64 (amd64) => Unknown/Multiple Comment: Not just Windows. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10796#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression -------------------------------------+------------------------------------- Reporter: erisco | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Template Haskell | Version: 7.8.3 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): -------------------------------------+------------------------------------- Comment (by RyanGlScott): One thing isn't clear to me about the changes proposed. We could certainly modify `dataToQa` so that `dataToExpQ` (and thus `liftData`) works with both function and constructor names. What about `dataToPatQ`, though? There's no way to pattern-match on an expression directly, so what would this translate to? {{{#!hs f :: Set Char -> Set Char f s@($(dataToPatQ (const Nothing) (fromList "test"))) = s }}} The only way I could envision this working is if it were translated to something like: {{{#!hs f :: Set Char -> Set Char f x | x == fromList "test" = x }}} which is reminiscent of how pattern-matching on literals works, I suppose. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10796#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression -------------------------------------+------------------------------------- Reporter: erisco | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Template Haskell | Version: 7.8.3 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): -------------------------------------+------------------------------------- Comment (by goldfire): Good point. But I'm not terribly concerned here. The current behavior of `dataToPatQ` in this situation (when it sees a function instead of a constructor) is to create some bogus Haskell. The new behavior of `dataToPatQ` in this situation will be to create some bogus Haskell. The bogus Haskell changes, but I don't think it's any worse. And, as you say, with this change, we could improve `dataToExpQ` to create correct Haskell. Perhaps better would be for calls to `dataToQa` to know when it's working with a pattern and fail more gracefully. That would indeed be an improvement. But I don't think that we should try too hard here. The `Data` instance involved is lying, calling something a constructor when it's not. If we can accommodate the lie easily -- as we can in `dataToExpQ` -- then great. Otherwise, I think it's OK to fail. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10796#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression -------------------------------------+------------------------------------- Reporter: erisco | Owner: RyanGlScott Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Template Haskell | Version: 7.8.3 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D1313 -------------------------------------+------------------------------------- Changes (by RyanGlScott): * owner: => RyanGlScott * differential: => Phab:D1313 Comment: I can agree that it's probably not worth the effort to make such patterns work, especially since we'd have to convert the subpatterns to expressions to make this work, which would probably require a rewrite of `dataToQa`... I'll just stick to the `dataToExpQ` case. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10796#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression -------------------------------------+------------------------------------- Reporter: erisco | Owner: RyanGlScott Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Template Haskell | Version: 7.8.3 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D1313 -------------------------------------+------------------------------------- Comment (by RyanGlScott): On the discussion for Phab:D1313, Richard noted that in order to fix this bug properly, it would be necessary for `template-haskell` to know precisely which identifiers correspond to variables, and which correspond to data constructors. This can be surprisingly tricky, since a litmus test for variables vs. constructors must take into account infix symbols and special characters (e.g., [https://ghc.haskell.org/trac/ghc/ticket/1103 Japanese katakana or hiragana]). Such a task seems best left to a function separate from `dataToQa`, but which one? There's [https://git.haskell.org/ghc.git/blob/ea4df12f7f3fc4d1d2af335804b8ec893f45550... startsVarSym, startsVarId, startsConSym, and startsConId] from `Lexeme` in GHC, but `template-haskell` can't depend on GHC. We ought not move these to `base` either, since that we need this functionality to compile stage 1. Therefore, it seems apt to move this to a package which both `ghc` and `template-haskell` could depend on. Luckily, there's some momentum behind this already: Simon PJ [https://phabricator.haskell.org/D1200#33621 suggested] reappropriating the `bin-package-db` package to become a library which contains functionality that is needed across multiple GHC boot libraries (including GHC itself). Less fortunately, we'd probably need to give it a new name to reflect this. Here is what I propose to resolve this quagmire: 1. Rename `bin-package-db` to `ghc-common` (other naming suggestions are welcome). 2. Move `startsVarSym`, `startsVarId`, `startsConSym`, `startsConId`, `startsVarSymASCII`, and `isVarSymChar` from `Lexeme` to `ghc-common`. There are other things that could be moved, but these would be enough to fix this ticket, and don't rely on a GHC internal data type (e.g., `FastString`). 3. Make `ghc` and `template-haskell` depend on `ghc-common`. No other changes to `ghc` should be necessary. 4. Use `startsVarSym` and `startsVarId` to check if a string corresponds to a variable name within `template-haskell`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10796#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression -------------------------------------+------------------------------------- Reporter: erisco | Owner: RyanGlScott Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Template Haskell | Version: 7.8.3 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D1313 -------------------------------------+------------------------------------- Comment (by goldfire): I approve this plan. Name suggestion: `ghc-boot`. It reflects the reality of the situation: it's a package needed "before" `ghc` proper. And it seems to wave a big flag saying "I'm an internal package. Don't look at me!" -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10796#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression
-------------------------------------+-------------------------------------
Reporter: erisco | Owner: RyanGlScott
Type: bug | Status: new
Priority: normal | Milestone: 8.0.1
Component: Template Haskell | Version: 7.8.3
Resolution: | Keywords: newcomer
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s): Phab:D1313
-------------------------------------+-------------------------------------
Comment (by Austin Seipp
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression -------------------------------------+------------------------------------- Reporter: erisco | Owner: RyanGlScott Type: bug | Status: closed Priority: normal | Milestone: 8.0.1 Component: Template Haskell | Version: 7.8.3 Resolution: fixed | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D1313 Wiki Page: | -------------------------------------+------------------------------------- Changes (by thoughtpolice): * status: new => closed * resolution: => fixed Comment: Thanks Ryan - I think this should be handled now, so closing this. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10796#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10796: Illegal data constructor name: `fromList' ... When splicing a TH expression
-------------------------------------+-------------------------------------
Reporter: erisco | Owner: RyanGlScott
Type: bug | Status: closed
Priority: normal | Milestone: 8.0.1
Component: Template Haskell | Version: 7.8.3
Resolution: fixed | Keywords: newcomer
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s): Phab:D1313
Wiki Page: |
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Comment (by Thomas Miedema
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