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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2021-02-02 10:36:57 +0000 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2021-02-06 09:27:28 -0500 |
| commit | 18313374e42925d1c7a8684b52e922689610574f (patch) | |
| tree | 19998a8c6a046215e303a592fd612e519499b5e3 | |
| parent | 7f3524efcbd58ca6837ec0ffca6ddd121d64e4de (diff) | |
| download | haskell-18313374e42925d1c7a8684b52e922689610574f.tar.gz | |
Fix buglet in expandSynTyCon_maybe
The fix for #17958, implemented in MR !2952, introduced a small bug
in GHC.Core.TyCon.expandSynTyCon_maybe, in the case of under-saturated
type synonyms.
This MR fixes the bug, very easy.
Fixes #19279
| -rw-r--r-- | compiler/GHC/Core/TyCon.hs | 11 | ||||
| -rw-r--r-- | testsuite/tests/ghci/scripts/T19279.script | 3 | ||||
| -rw-r--r-- | testsuite/tests/ghci/scripts/T19279.stdout | 3 | ||||
| -rwxr-xr-x | testsuite/tests/ghci/scripts/all.T | 1 |
4 files changed, 13 insertions, 5 deletions
diff --git a/compiler/GHC/Core/TyCon.hs b/compiler/GHC/Core/TyCon.hs index 4db3167bd7..efa6cfbcf7 100644 --- a/compiler/GHC/Core/TyCon.hs +++ b/compiler/GHC/Core/TyCon.hs @@ -2257,13 +2257,14 @@ expandSynTyCon_maybe -- type of the synonym (not yet substituted) -- and any arguments remaining from the -- application - --- ^ Expand a type synonym application, if any +-- ^ Expand a type synonym application +-- Return Nothing if the TyCon is not a synonym, +-- or if not enough arguments are supplied expandSynTyCon_maybe tc tys | SynonymTyCon { tyConTyVars = tvs, synTcRhs = rhs, tyConArity = arity } <- tc - = case tys of - [] -> Just ([], rhs, []) -- Avoid a bit of work in the case of nullary synonyms - _ -> case tys `listLengthCmp` arity of + = if arity == 0 + then Just ([], rhs, tys) -- Avoid a bit of work in the case of nullary synonyms + else case tys `listLengthCmp` arity of GT -> Just (tvs `zip` tys, rhs, drop arity tys) EQ -> Just (tvs `zip` tys, rhs, []) LT -> Nothing diff --git a/testsuite/tests/ghci/scripts/T19279.script b/testsuite/tests/ghci/scripts/T19279.script new file mode 100644 index 0000000000..b414e1dc8b --- /dev/null +++ b/testsuite/tests/ghci/scripts/T19279.script @@ -0,0 +1,3 @@ +type T a = a +:kind! T +:kind T diff --git a/testsuite/tests/ghci/scripts/T19279.stdout b/testsuite/tests/ghci/scripts/T19279.stdout new file mode 100644 index 0000000000..fe7fbbf9f8 --- /dev/null +++ b/testsuite/tests/ghci/scripts/T19279.stdout @@ -0,0 +1,3 @@ +T :: * -> * += T +T :: * -> * diff --git a/testsuite/tests/ghci/scripts/all.T b/testsuite/tests/ghci/scripts/all.T index 08a6c4ee6a..a85fe27fd3 100755 --- a/testsuite/tests/ghci/scripts/all.T +++ b/testsuite/tests/ghci/scripts/all.T @@ -328,4 +328,5 @@ test('T18755', normal, ghci_script, ['T18755.script']) test('T18828', normal, ghci_script, ['T18828.script']) test('T19197', normal, ghci_script, ['T19197.script']) test('T19158', normal, ghci_script, ['T19158.script']) +test('T19279', normal, ghci_script, ['T19279.script']) |