#10996: family is treated as keyword in types even without TypeFamilies enabled -------------------------------------+------------------------------------- Reporter: oerjan | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.10.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: GHC rejects | Test Case: type Test valid program | family = family Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by oerjan): As I said, in principle there may be no real ambiguity, but unfortunately it seems like the head of these constructions is parsed as a `type` (nonterminal) token, and the check for whether it is of the right form is only done ''after'' the `Happy` parsing: {{{ Prelude> :set -XTypeFamilies Prelude> type family' a = a <interactive>:28:6: Malformed head of type or class declaration: family' a Prelude> type family a = a <interactive>:30:13: Malformed head of type or class declaration: a }}} A token that parses those and only those `type`s that can appear as the head of these declarations (in particular, disallowing ''applied'' type variables) might solve this problem. (Unless, of course, there's some ambiguous case that I've forgotten, but that should hopefully show up as a reduce/* conflict.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10996#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler