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| author | Herbert Valerio Riedel <hvr@gnu.org> | 2015-01-21 08:21:36 +0100 |
|---|---|---|
| committer | Herbert Valerio Riedel <hvr@gnu.org> | 2015-01-22 22:36:24 +0100 |
| commit | 3df429e29b6fabda12af71091ba4ad1360f49b44 (patch) | |
| tree | 3fece93d426fbcd1d9e778d1f086318654a57839 /libraries/base/Data/Data.hs | |
| parent | e6756640bb410258837d186e8c2e339d6746dc11 (diff) | |
| download | haskell-3df429e29b6fabda12af71091ba4ad1360f49b44.tar.gz | |
Restore invariant in `Data (Ratio a)` instance
(2nd attempt, this time leaving the `Constr` using `":%"`)
The Data instance for `Ratio` just uses the raw `:%` constructor and
doesn't check that the result is reduced to normal form.
The fix is to add back the `Integral` constraint on the Data
instance (which was dropped in c409b6f30373535) and to use `%` rather
than `:%` in the `gfoldl` and `gunfold` implementation.
This restores the invariant and matches the behavior of "virtual
constructors" we've used to patch up such problems elsewhere.
This addresses #10011
Reviewed By: ekmett, austin
Differential Revision: https://phabricator.haskell.org/D625
Diffstat (limited to 'libraries/base/Data/Data.hs')
| -rw-r--r-- | libraries/base/Data/Data.hs | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/libraries/base/Data/Data.hs b/libraries/base/Data/Data.hs index dce610b1d7..6961b250b5 100644 --- a/libraries/base/Data/Data.hs +++ b/libraries/base/Data/Data.hs @@ -1064,10 +1064,10 @@ ratioConstr = mkConstr ratioDataType ":%" [] Infix ratioDataType :: DataType ratioDataType = mkDataType "GHC.Real.Ratio" [ratioConstr] -instance Data a => Data (Ratio a) where - gfoldl k z (a :% b) = z (:%) `k` a `k` b +instance (Data a, Integral a) => Data (Ratio a) where + gfoldl k z (a :% b) = z (%) `k` a `k` b toConstr _ = ratioConstr - gunfold k z c | constrIndex c == 1 = k (k (z (:%))) + gunfold k z c | constrIndex c == 1 = k (k (z (%))) gunfold _ _ _ = error "Data.Data.gunfold(Ratio)" dataTypeOf _ = ratioDataType |