#10747: Infix pattern synonyms fail to parse (regression) -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by rwbarton): Are you sure about the version numbers? I see it working in 7.8, but failing in 7.10 and HEAD. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10747#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10747: Infix pattern synonyms fail to parse (regression) -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by rwbarton): * priority: normal => high * version: 7.11 => 7.10.1 Old description:

{{{#!hs {-# LANGUAGE PatternSynonyms #-} pattern head `Cons` tail = head : tail }}}

In v7.11 I get: {{{ [1 of 1] Compiling Main ( pat.hs, interpreted )

pat.hs:2:14: parse error on input ?`?

}}}

In v7.10 I get: {{{ *Main> :set -XPatternSynonyms *Main> let h `Cons` t = "ht" *Main> h 'h' *Main> t "t" }}}

New description: {{{#!hs {-# LANGUAGE PatternSynonyms #-} pattern head `Cons` tail = head : tail }}} In v7.10 I get: {{{ [1 of 1] Compiling Main ( pat.hs, interpreted ) pat.hs:2:14: parse error on input ?`? }}} In v7.8 I get: {{{ [1 of 1] Compiling Main ( ph.hs, interpreted ) Ok, modules loaded: Main. *Main> :set -XPatternSynonyms *Main> let h `Cons` t = "ht" *Main> h 'h' *Main> t "t" }}} -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10747#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10747: Infix pattern synonyms fail to parse (regression) -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: high | Milestone: 7.10.3 Component: Compiler | Version: 7.10.1 (Parser) | Keywords: Resolution: | PatternSynonyms Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): -------------------------------------+------------------------------------- Comment (by heisenbug): Maybe I have to enable `TypeOperators` too? '''' No, same error message. {{{ error: parse error on input ?`? Failed, modules loaded: none. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10747#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10747: Infix pattern synonyms fail to parse (regression) -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: high | Milestone: 7.10.3 Component: Compiler | Version: 7.10.1 (Parser) | Keywords: Resolution: | PatternSynonyms Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): -------------------------------------+------------------------------------- Comment (by heisenbug): Replying to [comment:6 mpickering]:

I'm yet to look at this in detail but I suspect that this was never meant to work. I assumed that infix pattern synonyms definitions were meant to be like infix data constructor definitions.

Then it should work: {{{ $ ghci GHCi, version 7.11.20150928: http://www.haskell.org/ghc/ :? for help Prelude> data List a = Nil | a `Cons` List a deriving Show Prelude> 4 `Cons` Nil 4 `Cons` Nil }}} This has been working for ages! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10747#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10747: Infix pattern synonyms fail to parse (regression) -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: mpickering Type: bug | Status: new Priority: high | Milestone: 7.10.3 Component: Compiler | Version: 7.10.1 (Parser) | Keywords: Resolution: | PatternSynonyms Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D1295 -------------------------------------+------------------------------------- Changes (by mpickering): * differential: => Phab:D1295 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10747#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10747: Infix pattern synonyms fail to parse (regression) -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: mpickering Type: bug | Status: merge Priority: high | Milestone: 7.10.3 Component: Compiler | Version: 7.10.1 (Parser) | Keywords: Resolution: | PatternSynonyms Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | patsyn/should_compile/T10747 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D1295 Wiki Page: | -------------------------------------+------------------------------------- Changes (by thomie): * status: new => merge * testcase: => patsyn/should_compile/T10747 Comment: One line fix, should be easy to merge. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10747#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler