diff options
Diffstat (limited to 'testsuite/tests/typecheck/should_compile/tc201.hs')
-rw-r--r-- | testsuite/tests/typecheck/should_compile/tc201.hs | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/testsuite/tests/typecheck/should_compile/tc201.hs b/testsuite/tests/typecheck/should_compile/tc201.hs new file mode 100644 index 0000000000..c60aa85406 --- /dev/null +++ b/testsuite/tests/typecheck/should_compile/tc201.hs @@ -0,0 +1,25 @@ +{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, + ExistentialQuantification, FlexibleContexts #-} + +{- Email 30 Jan 2006 + +> the attached program compiles under GHC, but not with Hugs. as far as +> i see, Hugs don't use dependencies in class headers to figure out that +> there is only one "vMkIOError" that can be called in the last +> definition + +OK, I think it's a bug (though the example is bizarre). Sadly Hugs's +support for FDs is rough around the edges (and unlikely to improve +soon). + +-} + +module ShoudlCompile where + + class (Monad m) => Stream m h | h->m where + vMkIOError :: h -> Int + + data BinHandle = forall h . Stream IO h => BinH h + + instance Stream IO BinHandle where + vMkIOError (BinH h) = vMkIOError h |