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| author | Sebastian Graf <sebastian.graf@kit.edu> | 2019-10-25 11:20:48 +0200 |
|---|---|---|
| committer | Sebastian Graf <sebastian.graf@kit.edu> | 2019-10-25 17:15:43 +0200 |
| commit | bf053189060bacded949050f4efeeb279dc23cc4 (patch) | |
| tree | ecda5e5bc78d0353d16eb57ffb0efa1ef6037030 /compiler/GHC/Hs.hs | |
| parent | 6824f29aebd28571db118eb6877ef04eda630871 (diff) | |
| download | haskell-wip/flexible-outputable.tar.gz | |
Use FlexibleInstances for `Outputable (* p)` instead of match-all instances with equality constraintswip/flexible-outputable
In #17304, Richard and Simon dicovered that using `-XFlexibleInstances`
for `Outputable` instances of AST data types means users can provide orphan
`Outputable` instances for passes other than `GhcPass`.
Type inference doesn't currently to suffer, and Richard gave an example
in #17304 that shows how rare a case would be where the slightly worse
type inference would matter.
So I went ahead with the refactoring, attempting to fix #17304.
Diffstat (limited to 'compiler/GHC/Hs.hs')
| -rw-r--r-- | compiler/GHC/Hs.hs | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/compiler/GHC/Hs.hs b/compiler/GHC/Hs.hs index aa345f1476..103539a41b 100644 --- a/compiler/GHC/Hs.hs +++ b/compiler/GHC/Hs.hs @@ -118,7 +118,7 @@ deriving instance Data (HsModule GhcPs) deriving instance Data (HsModule GhcRn) deriving instance Data (HsModule GhcTc) -instance (p ~ GhcPass pass, OutputableBndrId p) => Outputable (HsModule p) where +instance (OutputableBndrId p) => Outputable (HsModule (GhcPass p)) where ppr (HsModule Nothing _ imports decls _ mbDoc) = pp_mb mbDoc $$ pp_nonnull imports |