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.

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