#15952: Reduce zonking-related invariants in the type checker -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.6.3 Component: Compiler | Version: 8.6.2 Resolution: | Keywords: 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 simonpj): I propose dividing Step 2 into two. * '''Step 2a''': make `tcTypeKind` monadic, and get rid of the `naked` functions. This will fix #15799 and #15918. * '''Step 2b''': make `substTy` monadic too. After Step 2a, we still have * Invariant `(ForallInv)`: in a 'forall' type `forall a. blah`, all occurrences of `a` should still be visible in `blah` without zonking. So we don't need to make `substTy` monadic in Step 2a. Personally I think that Step 2b might not be worth the bother. Maintaining `(ForallInv)` is really not hard, whereas maintaining `Note [The well-kinded type invariant]` is extremely tricky. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15952#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler