diff options
| author | Vladislav Zavialov <vlad.z.4096@gmail.com> | 2019-12-02 23:10:33 +0300 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2019-12-05 16:07:49 -0500 |
| commit | 3354c68ec6c90bbccc0f361aa7973eeb75ea229c (patch) | |
| tree | b9c5e2f9627b25b6d7bdf745b281b6771b8d5990 /compiler/GHC/Hs | |
| parent | c4ca29c796fa86ad9d5cd4dfa1a5cdd4e0565fb0 (diff) | |
| download | haskell-3354c68ec6c90bbccc0f361aa7973eeb75ea229c.tar.gz | |
Pretty-printing of the * kind
Before this patch, GHC always printed the * kind unparenthesized.
This led to two issues:
1. Sometimes GHC printed invalid or incorrect code.
For example, GHC would print: type F @* x = x
when it meant to print: type F @(*) x = x
In the former case, instead of a kind application we were getting a
type operator (@*).
2. Sometimes GHC printed kinds that were correct but hard to read.
Should Either * Int be read as Either (*) Int
or as (*) Either Int ?
This depends on whether -XStarIsType is enabled, but it would be
easier if we didn't have to check for the flag when reading the code.
We can solve both problems by assigning (*) a different precedence. Note
that Haskell98 kinds are not affected:
((* -> *) -> *) -> * does NOT become (((*) -> (*)) -> (*)) -> (*)
The parentheses are added when (*) is used in a function argument
position:
F * * * becomes F (*) (*) (*)
F A * B becomes F A (*) B
Proxy * becomes Proxy (*)
a * -> * becomes a (*) -> *
Diffstat (limited to 'compiler/GHC/Hs')
| -rw-r--r-- | compiler/GHC/Hs/Types.hs | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/compiler/GHC/Hs/Types.hs b/compiler/GHC/Hs/Types.hs index e92928c78f..324b1dd3d2 100644 --- a/compiler/GHC/Hs/Types.hs +++ b/compiler/GHC/Hs/Types.hs @@ -1676,7 +1676,7 @@ hsTypeNeedsParens p = go go (HsExplicitTupleTy{}) = False go (HsTyLit{}) = False go (HsWildCardTy{}) = False - go (HsStarTy{}) = False + go (HsStarTy{}) = p >= starPrec go (HsAppTy{}) = p >= appPrec go (HsAppKindTy{}) = p >= appPrec go (HsOpTy{}) = p >= opPrec |