c8a589d2b31a67544a60c27f2ab3c6307a3368e3
[ghc.git] / testsuite / tests / typecheck / should_compile / Tc173a.hs
1 module Tc173a where
2
3 class FormValue value where
4 isFormValue :: value -> ()
5 isFormValue _ = ()
6
7 class FormTextField value
8
9 instance FormTextField String
10
11 instance FormTextField value => FormTextFieldIO value
12
13 class FormTextFieldIO value
14
15 instance FormTextFieldIO value => FormValue value
16
17 instance FormTextFieldIO value => FormTextFieldIO (Maybe value)