#11224: Program doesn't preserve semantics after pattern synonym inlining. -------------------------------------+------------------------------------- Reporter: anton.dubovik | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Windows | Architecture: x86_64 Type of failure: Incorrect result | (amd64) at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by mpickering): I'm a bit out of my depth here but an immediate problem is that it's not possible to write down the correct type signature for `PRead`. I think it should be `pattern PRead :: Read a => a -> String` which GHC rejects because the required constraints mention the existentially quantified `a`. It is even more baffling though that with this type signature that GHC still fails to typecheck the code, it only typechecks with the inferred type. I'm doing a bit more investigating now but I think only Richard or Simon will be able to give a better account. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11224#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler