SLIDE 1
Visib isible Dep e Depen ende dent nt Quan uantifjcati tifjcation
- n (V
(VDQ) Q)
Ryan Scott
PL Wonks March 8, 2019
Visib isible Dep e Depen ende dent nt Quan uantifjcati - - PowerPoint PPT Presentation
Visib isible Dep e Depen ende dent nt Quan uantifjcati - - PowerPoint PPT Presentation
Visib isible Dep e Depen ende dent nt Quan uantifjcati tifjcation on (V (VDQ) Q) Ryan Scott PL Wonks March 8, 2019 Code t Code time! me! The VDQ p he VDQ pat atch ch --- a/compiler/parser/Parser.y +++
SLIDE 2
SLIDE 3
SLIDE 4
SLIDE 5
SLIDE 6
SLIDE 7
SLIDE 8
SLIDE 9
SLIDE 10
SLIDE 11
SLIDE 12
The VDQ p he VDQ pat atch ch
SLIDE 13
- -- a/compiler/parser/Parser.y
+++ b/compiler/parser/Parser.y +forall_vis_flag :: { ForallVisFlag } + : '.' { ForallInvis } + | '->' { ForallVis } +
- - A ctype is a for-all type
ctype :: { LHsType GhcPs }
- : 'forall' tv_bndrs '.' ctype {% ...
+ : 'forall' tv_bndrs forall_vis_flag ctype {% ...
- HsForAllTy { hst_bndrs = $2
+ HsForAllTy { hst_fvf = $3 + , hst_bndrs = $2
SLIDE 14
- -- a/compiler/typecheck/TcHsType.hs
+++ b/compiler/typecheck/TcHsType.hs
- -------- Foralls
- tc_hs_type forall@(HsForAllTy { ... })
+tc_hs_type forall@(HsForAllTy { hst_fvf = fvf, ... }) = do { ...
- ; let bndrs = mkTyVarBinders Specified tvs'
+ ; let argf = case fvf of + ForallVis -> Required + ForallInvis -> Specified + bndrs = mkTyVarBinders argf tvs'
SLIDE 15
forall k -> k -> Type
SLIDE 16
forall k -> k -> Type {-# LANGUAGE ExplicitForAll #-}
SLIDE 17
Code t Code time! me!
(agai (again)
SLIDE 18
SLIDE 19
data F :: forall k -> k -> Type
SLIDE 20
data F :: forall k -> k -> Type sortOfId :: forall a -> a -> a
SLIDE 21
data F :: forall k -> k -> Type sortOfId :: forall a -> a -> a
SLIDE 22
vdqAllowed :: UserTypeCtxt -> Bool
SLIDE 23
vdqAllowed :: UserTypeCtxt -> Bool
- - Currently allowed in the kinds of types...
vdqAllowed (KindSigCtxt {}) = True vdqAllowed (TySynCtxt {}) = True
SLIDE 24
vdqAllowed :: UserTypeCtxt -> Bool
- - Currently allowed in the kinds of types...
vdqAllowed (KindSigCtxt {}) = True vdqAllowed (TySynCtxt {}) = True
- - ...but not in the types of terms.
vdqAllowed (FunSigCtxt {}) = False vdqAllowed (InstDeclCtxt {}) = False
SLIDE 25
SLIDE 26
SLIDE 27
- An important step towards dependent types in Haskell
- Amaze your friends, impress your coworkers, wow!