#10189: explicit promotions of prefix data constructors can't be parsed naturally -------------------------------------+------------------------------------- Reporter: Kinokkory | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 (Parser) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | Blocking: Blocked By: | Differential Revisions: Related Tickets: #10188 | -------------------------------------+------------------------------------- Changes (by Kinokkory): * related: => #10188 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10189#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10189: explicit promotions of prefix data constructors can't be parsed naturally -------------------------------------+------------------------------------- Reporter: Kinokkory | Owner: Kinokkory Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.8.4 (Parser) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | Blocking: Blocked By: | Differential Revisions: Related Tickets: #10188 | -------------------------------------+------------------------------------- Changes (by Kinokkory): * owner: => Kinokkory * milestone: => 7.12.1 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10189#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10189: explicit promotions of prefix data constructors can't be parsed naturally -------------------------------------+------------------------------------- Reporter: Kinokkory | Owner: Kinokkory Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.8.4 (Parser) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | Blocking: Blocked By: | Differential Revisions: Related Tickets: #10188 | -------------------------------------+------------------------------------- Comment (by simonpj): Would it really be so bad to change it so that the tick goes inside the parens? It'll only affect people using (a) promotion, (b) type operators, and (c) prefix use of same. I'd prefer just to get it right. I think of `':` as the name of the promoted constructor, and if you want it prefix you should wrap it in parens. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10189#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10189: explicit promotions of prefix data constructors can't be parsed naturally -------------------------------------+------------------------------------- Reporter: Kinokkory | Owner: Kinokkory Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.8.4 (Parser) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | Blocking: Blocked By: | Differential Revisions: Related Tickets: #10188 | -------------------------------------+------------------------------------- Comment (by simonpj): Ah well making `'` scope over a ''term'', not just a ''name'', is a whole new unexplored ball of wax. I'd rather make what we have fit together nicely, otherwise we pay now for a distant and uncertain future benefit. We can jump future bridges when we come to them. I don't think we have enough legacy code to make wibblification on existing packages into a serious problem. I suppose we could allow both forms for a while, but emit deprecation messages for the old one. But I don't think that even that is worth the trouble. Let's just make the change: * `(':)`, not `'(:)` * {{{`'Bar`}}}, not {{{'`Bar`}}}. Can someone do this? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10189#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10189: explicit promotions of prefix data constructors can't be parsed naturally -------------------------------------+------------------------------------- Reporter: Kinokkory | Owner: Kinokkory Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.8.4 (Parser) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | Blocking: Blocked By: | Differential Revisions: Related Tickets: #10188 | -------------------------------------+------------------------------------- Old description:

When used as an infix operator, a data constructor is explicitly promoted simply with `'` prefixed, but when used as a prefix operator enclosed between `(` and `)`, it is explicitly promoted only with `'` put before `(`, not before the constructor.

On the other hand, messages of GHC and GHCi indicate that a data constructor operator in a prefix form is promoted by putting `'` before the constructor! (as in `forall (k :: BOX) (k :: BOX). (':*)` below.)

I believe that this is a matter of parsing. The parser should admit `(':*)` as well as `'(:*)` for the naturalness of the syntax.

In a GHCi:

{{{#!hs

...

:set -XDataKinds -XTypeOperators data a :* b = a :* b :kind! Int :* Int Int :* Int :: * = Int :* Int :kind! Int ':* Int Int ':* Int :: * :* * = Int ':* Int :kind! (:*) (:*) :: * -> * -> * = (:*) :kind! '(:*) '(:*) :: k -> k1 -> k :* k1 = forall (k :: BOX) (k :: BOX). (':*) :kind! (':*)

<interactive>:1:3: parse error on input ‘:*’ }}}

(By the way I assume that Template Haskell quotes (`'function` and `''Type`) are parsed by the same mechanism as the one for the explicit promotion syntax. I hope both styles of quotes for prefix operators will be admitted because currently only the `'(` `''(` style is admitted.)

New description: When used as an infix operator, a data constructor is explicitly promoted simply with `'` prefixed, but when used as a prefix operator enclosed between `(` and `)`, it is explicitly promoted only with `'` put before `(`, not before the constructor. On the other hand, messages of GHC and GHCi indicate that a data constructor operator in a prefix form is promoted by putting `'` before the constructor! (as in `forall (k :: BOX) (k :: BOX). (':*)` below.) I believe that this is a matter of parsing. The parser should admit `(':*)` as well as `'(:*)` for the naturalness of the syntax. In a GHCi: {{{#!hs

:set -XDataKinds -XTypeOperators data a :* b = a :* b :kind! Int :* Int Int :* Int :: * = Int :* Int :kind! Int ':* Int Int ':* Int :: * :* * = Int ':* Int :kind! (:*) (:*) :: * -> * -> * = (:*) :kind! '(:*) '(:*) :: k -> k1 -> k :* k1 = forall (k :: BOX) (k :: BOX). (':*) :kind! (':*)

<interactive>:1:3: parse error on input ‘:*’ }}} -- Comment (by Kinokkory): (Removed the mention about Template Haskell syntax.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10189#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10189: explicit promotions of prefix data constructors can't be parsed naturally -------------------------------------+------------------------------------- Reporter: Kinokkory | Owner: Kinokkory Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 7.8.4 (Parser) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: #10188 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by dfeuer): * cc: dfeuer (added) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10189#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler