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authorNiklas Haas <git@nand.wakku.to>2014-03-31 20:02:36 +0200
committerNiklas Haas <git@nand.wakku.to>2014-03-31 20:09:58 +0200
commita6e36fc8cde675c2b7b2bc8f519221c93f20f207 (patch)
treedda96a33a1be220e83fb810c88b96e1f13aa297e /html-test/src
parentd6cf6f9c75e08ce1760c2dbdee81775ba97a5f0c (diff)
Crash when exporting record selectors of data family instances
This fixes bug #294. This also fixes a related but never-before-mentioned bug about the display of GADT record selectors with non-polymorphic type signatures. Note: Associated data type constructors fail to show up if nothing is exported that they could be attached to. Exporting any of the data types in the instance head, or the class + data family itself, causes them to show up, but in the absence of either of these, exporting just the associated data type with the constructor itself will result in it being hidden. The only scenario I can come up that would involve this kind of situation involved OverlappingInstances, and even then it can be mitigated by just exporting the class itself, so I'm not going to solve it since the logic would most likely be very complicated.
Diffstat (limited to 'html-test/src')
-rw-r--r--html-test/src/Bug294.hs37
1 files changed, 37 insertions, 0 deletions
diff --git a/html-test/src/Bug294.hs b/html-test/src/Bug294.hs
new file mode 100644
index 00000000..4f874705
--- /dev/null
+++ b/html-test/src/Bug294.hs
@@ -0,0 +1,37 @@
+{-# LANGUAGE TypeFamilies, FlexibleInstances, GADTs #-}
+-- This tests that we are able to extract record selectors for
+-- associated types when the type itself is not exported. Making this
+-- bug exhibit is very simple: simply mention a record field defined
+-- inside of the associated type anywhere in the export list.
+--
+-- Note: ProblemCtor only shows up when T or A are exported but PolyCtor
+-- only shows up when the class is exported as well, since it's polymorphic.
+module Bug294 ( A, problemField, problemField', gadtField
+ , TP(ProblemCtor), DP(ProblemCtor'), TO'(PolyCtor)) where
+
+data A
+
+class T t where
+ data TO t :: *
+ data TP t :: *
+
+ t :: t
+
+instance T A where
+ data TO A = TA { problemField :: A }
+ data TP A = ProblemCtor A
+
+data family DO t :: *
+data family DP t :: *
+
+data instance DO A = DA { problemField' :: A }
+data instance DP A = ProblemCtor' A
+
+data GADT :: * -> * where
+ Ctor :: { gadtField :: A } -> GADT A
+
+class T' t where
+ data TO' t :: *
+
+instance T' a where
+ data TO' a = PolyCtor