#15791: typeKind confuses Type and Constraint -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Branch: Wiki Page: | wip/T15791 -------------------------------------+------------------------------------- Comment (by goldfire): Here are the typing rules, as I see it: {{{ t1 : Constraint t2 : TYPE rep -- rep is a metavariable ---------------- t1 => t2 : Type t1 : Constraint t2 : Constraint --------------------- t1 => t2 : Constraint ty : TYPE rep `a` is not free in rep ----------------------- forall a. ty : TYPE rep ty : Constraint ------------------------- forall a. ty : Constraint }}} The rules might be missing some side conditions for type safety, etc., but this should be enough to get `typeKind` working. Specifically: because the kind of `a` is `TYPE blah`, then `HasCallStack => a` has kind `Type`. Maybe you were thinking that `t1 => t2` has the kind of `t2`? That wouldn't work. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15791#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler