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| author | Sebastian Graf <sebastian.graf@kit.edu> | 2019-10-25 11:20:48 +0200 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2019-10-28 09:22:35 -0400 |
| commit | e951f219597a3e8209abd62f85c717865f7445ca (patch) | |
| tree | f1036c6a31758fb835179fc147ab4830c0b61c20 /compiler/GHC/Hs.hs | |
| parent | e0e0485634d9a047b43da958c09e3bf6c5937c0f (diff) | |
| download | haskell-e951f219597a3e8209abd62f85c717865f7445ca.tar.gz | |
Use FlexibleInstances for `Outputable (* p)` instead of match-all instances with equality constraints
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 |