#12428: Allow pattern synonyms to optionally carry coerceability -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: feature | Status: new request | Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Aside from their more interesting abilities, pattern synonyms can be used for name management. For example, if a module exports a type with a data constructor named `A`, and also re-exports a type with a data constructor named `A`, it can use a pattern synonym to rename the imported constructor. If the type is a `newtype`, this pattern synonym will not carry coerceability. Sometimes, this is exactly what one would desire (an "unsafe" module breaking through a newtype abstraction may wish to allow importers to confine coerceability). Other times, it's not (pattern synonym just for name control). When defining a pattern synonym for a type in a module in which that type is coerceable, it would be nice to be able to tell GHC that the pattern synonym should carry coerceability. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12428 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler