#10607: Auto derive from top to bottom -------------------------------------+------------------------------------- Reporter: songzh | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Resolution: | Keywords: deriving, | typeclass, auto 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 rwbarton): Sounds reasonable.
(Syntax bikeshedding is welcome.)
Well, since you asked... how about `deriving instance _ => C (T a b c)`, which is currently accepted by the parser (and probably won't be too taxing for other tools) but rejected later with the error {{{ C.hs:8:19: error: Wildcard ‘_’ not allowed in In a deriving declaration for ‘C’ | 8 | deriving instance _ => C (T a b c) | ^ }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10607#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler