#10653: PatternSynonyms should be imported/exported as part of the wildcard notation -------------------------------------+------------------------------------- Reporter: gridaphobe | Owner: Type: feature request | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.11 Resolution: | Keywords: pattern | synonyms Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by rwbarton): I think Richard's proposal already allows this, but I would add that there is likely some real value in allowing a module to associate a pattern synonym with a type constructor even when the module is not the one in which the type constructor is defined. It's a common organization to put a bunch of types in a single, sometimes "internal", module (to avoid import loops) and then define functions involving those types in many different modules (to avoid having one giant module of doom). Pattern synonyms can involve nontrivial functions if they use view patterns (think of Data.Seq for instance) so it would be useful to associate a pattern synonym with a data type in a top-level module that consists of re-exports. On the subject of requiring pattern synonyms attached to type constructors to have that type constructor in outermost position in their type, what about polymorphic pattern synonyms? Doesn't it make sense to write something like {{{ pattern Nil = (Foldable.null -> True) }}} where `Nil` matches an expression of type `Foldable t => t a`? What is the rule then? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10653#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler