#16185: Add an AnonArgFlag to FunTy -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 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: | -------------------------------------+------------------------------------- Description changed by simonpj: Old description:
In Trac #15952 Richard and I agreed that it makes sense to add a flag to `FunTy` to distinguish `(->)` from `(=>)`. This ticket tracks progress.
See [ticket:15952#comment:7] and [ticket:15952#comment:8].
Main changes:
* Define `AnonArgFlag` in `Var`, alongside `ArgFlag` {{{ data AnonArgFlag = VisArg -- Used for (->): an ordinary non-dependent arrow -- The argument is visible in source code | InvisArg -- Used for (=>): a non-dependent predicate arrow -- The argument is invisible in source code }}}
* `Type` looks like this {{{ data Type = ...
| FFunTy -- ^ t1 -> t2 Very common, so an important special case -- FFunTy for "full function type"; see pattern synonym for FunTy { ft_af :: AnonArgFlag -- Is this (->) or (=>)? , ft_arg :: Type -- Argument type , ft_res :: Type } -- Resuult type }}}
* Add a uni-directional pattern synonym for the old `FunTy` {{{ pattern FunTy :: Type -> Type -> Type pattern FunTy arg res <- FFunTy { ft_arg = arg, ft_res = res } }}}
Everything else follows routinely.
A huge win is that `isPredTy` vanishes almost completely.
New description: In Trac #15952 Richard and I agreed that it makes sense to add a flag to `FunTy` to distinguish `(->)` from `(=>)`. This ticket tracks progress. See [ticket:15952#comment:7] and [ticket:15952#comment:8]. Main changes: * Define `AnonArgFlag` in `Var`, alongside `ArgFlag` {{{ data AnonArgFlag = VisArg -- Used for (->): an ordinary non-dependent arrow -- The argument is visible in source code | InvisArg -- Used for (=>): a non-dependent predicate arrow -- The argument is invisible in source code }}} * `Type` looks like this {{{ data Type = ... | FFunTy -- ^ t1 -> t2 Very common, so an important special case -- FFunTy for "full function type"; see pattern synonym for FunTy { ft_af :: AnonArgFlag -- Is this (->) or (=>)? , ft_arg :: Type -- Argument type , ft_res :: Type } -- Resuult type }}} I'm using a record here to anticipate Linear Haskell, which will add a multiplicity field to `FFunTy`. * Add a uni-directional pattern synonym for the old `FunTy` {{{ pattern FunTy :: Type -> Type -> Type pattern FunTy arg res <- FFunTy { ft_arg = arg, ft_res = res } }}} Everything else follows routinely. A huge win is that `isPredTy` vanishes almost completely. -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16185#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler