#10823: Expose keepAlive to Template Haskell -------------------------------------+------------------------------------- Reporter: spinda | Owner: Type: feature request | Status: new Priority: normal | Milestone: 7.12.1 Component: Template Haskell | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by goldfire): Replying to [comment:4 spinda]:
Is the use of type-level literals essential here? That requires the user to have {{{DataKinds}}} enabled. Otherwise, the hack can fill our use case, I think.
No. It's just a convenient way to make sure that the instance head is unique. Any such mechanism should work.
On the other hand, I worry about Template Haskell code having to depend
too much on tricks that happen to work but aren't a guaranteed, stable, documented part of the interface. Agreed. Except that this is depending on a guaranteed, stable, documented feature: that ''all'' instance are always exported from a module. Thus if a definition is mentioned in an instance, GHC will never drop it. So this isn't a TH hack so much, but a GHC language hack.
//That said//, as I write this, I've realized that there may be another way to approach our particular issue. {{{[lq| inline gt |]}}} attaches an annotation to {{{gt}}}, so perhaps the solution should be to tell the desugarer not to consider any function with an annotation attached as dead code.
This is ''much'' better. Care to repurpose the ticket? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10823#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler