But this idea opens up a new, heretofore undiscussed possibility, that of a pattern synonym that cannot be used as a pattern. In other words, it would just be a normal Haskell variable, except with a capitalized identifier. I personally think this is one bridge too far, encouraging
#8581: Pattern synonym used in an expression context could have different constraints to pattern used in a pattern context -------------------------------------+------------------------------------- Reporter: cactus | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: Resolution: | Keywords: | PatternSynonyms Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): Replying to [comment:40 goldfire]: people to use a capitalized word for ordinary functions. I think this would be confusing, and for what benefit? It emphasizes the orthogonality of pattern synonyms and constructor synonyms; I tend to find orthogonal features easier to understand. The current reuse of the `where` keyword to add a constructor synonym is also troubling. It would feel cleaner to me to let these be completely separate declarations. BTW, what ever happened to the idea of letting a module re-export a type and associate pattern synonyms with it? I lost track of that and haven't had a chance to upgrade to 8.0 yet. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8581#comment:41 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler