#14478: Abstract pattern synonyms (for hsig and hs-boot) -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 (Type checker) | Keywords: backpack | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Most declaration forms (data types, values, type families, etc) support forward declaration in hs-boot/hsig files. However, pattern synonyms do not. This seems like a major omission! Some problems to solve: * The obvious syntax `pattern Foo :: pat_ty` is insufficient to specify whether or not a pattern is bidirectional or unidirectional. How should this be represented syntactically? * What is the interaction with bundling? Should it be possible to export a bundle of abstract pattern synonyms, with the intent that this means an implementation must also have bundled them together * See also #12717; abstract pattern synonym should be implementable with a plain old constructor -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14478 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler