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| author | Chaitanya Koparkar <ckoparkar@gmail.com> | 2018-08-27 14:07:08 +0200 |
|---|---|---|
| committer | Krzysztof Gogolewski <krz.gogolewski@gmail.com> | 2018-08-27 14:07:08 +0200 |
| commit | 2d953a60489ba30433e5f2fe27c50aa9da75f802 (patch) | |
| tree | 13c01c51de369cd603bb1fb42f2775f81da36ad8 | |
| parent | 6e765aebbe0a565f2476b522a49faf8edb9a93ee (diff) | |
| download | haskell-2d953a60489ba30433e5f2fe27c50aa9da75f802.tar.gz | |
Fix #10859 by using foldr1 while deriving Eq instances
Summary:
Previously, we were using foldl1 instead, which led to the derived
code to be wrongly associated.
Test Plan: ./validate
Reviewers: RyanGlScott, nomeata, simonpj, bgamari
Reviewed By: RyanGlScott, nomeata
Subscribers: rwbarton, carter
GHC Trac Issues: #10859
Differential Revision: https://phabricator.haskell.org/D5104
| -rw-r--r-- | compiler/typecheck/TcGenDeriv.hs | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/compiler/typecheck/TcGenDeriv.hs b/compiler/typecheck/TcGenDeriv.hs index e74ae32c7a..1debdddd7d 100644 --- a/compiler/typecheck/TcGenDeriv.hs +++ b/compiler/typecheck/TcGenDeriv.hs @@ -214,7 +214,9 @@ gen_Eq_binds loc tycon = do where nested_eq_expr [] [] [] = true_Expr nested_eq_expr tys as bs - = foldl1 and_Expr (zipWith3Equal "nested_eq" nested_eq tys as bs) + = foldr1 and_Expr (zipWith3Equal "nested_eq" nested_eq tys as bs) + -- Using 'foldr1' here ensures that the derived code is correctly + -- associated. See Trac #10859. where nested_eq ty a b = nlHsPar (eq_Expr tycon ty (nlHsVar a) (nlHsVar b)) |