#16311: Suggest -XExistentialQuantification for 'forall' in data declarations -------------------------------------+------------------------------------- Reporter: int-index | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 (Parser) | 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: -------------------------------------+------------------------------------- Phab:D5180 introduced a slight regression to the error messages. In this code {{{#!hs data T = forall a. MkT a }}} GHC used to complain {{{ rnfail053.hs:5:10: Not a data constructor: ‘forall’ Perhaps you intended to use ExistentialQuantification }}} but then the message has become {{{ rnfail053.hs:5:18: error: Illegal symbol '.' in type Perhaps you intended to use RankNTypes or a similar language extension to enable explicit-forall syntax: forall <tvs>. <type> }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16311 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler