[commit: ghc] ghc-7.10: Regression test for Trac #10390 (9b0d901)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : ghc-7.10
Link       : http://ghc.haskell.org/trac/ghc/changeset/9b0d901bc996ee21979e86c71a90f404a5225e86/ghc

>---------------------------------------------------------------

commit 9b0d901bc996ee21979e86c71a90f404a5225e86
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Thu May 7 16:46:02 2015 +0100

    Regression test for Trac #10390


>---------------------------------------------------------------

9b0d901bc996ee21979e86c71a90f404a5225e86
 testsuite/tests/typecheck/should_compile/T10390.hs | 16 ++++++++++++++++
 testsuite/tests/typecheck/should_compile/all.T     |  1 +
 2 files changed, 17 insertions(+)

diff --git a/testsuite/tests/typecheck/should_compile/T10390.hs b/testsuite/tests/typecheck/should_compile/T10390.hs
new file mode 100644
index 0000000..e0648c9
--- /dev/null
+++ b/testsuite/tests/typecheck/should_compile/T10390.hs
@@ -0,0 +1,16 @@
+{-# LANGUAGE RankNTypes #-}
+
+module T10390 where
+
+class ApPair r where
+  apPair :: (forall a . (ApPair a, Num a) => Maybe a) -> Maybe r
+
+instance (ApPair a, ApPair b) => ApPair (a,b) where
+  apPair = apPair'
+
+apPair' :: (ApPair b, ApPair c)
+        => (forall a . (Num a, ApPair a) => Maybe a) -> Maybe (b,c)
+            -- NB constraints in a different order to apPair
+apPair' f =  let (Just a) = apPair f
+                 (Just b) = apPair f
+          in Just $ (a, b)
diff --git a/testsuite/tests/typecheck/should_compile/all.T b/testsuite/tests/typecheck/should_compile/all.T
index bf0e0a0..33fff94 100644
--- a/testsuite/tests/typecheck/should_compile/all.T
+++ b/testsuite/tests/typecheck/should_compile/all.T
@@ -446,3 +446,4 @@ test('T10109', normal, compile, [''])
 test('T10335', normal, compile, [''])
 test('T10489', normal, compile, [''])
 test('T10564', normal, compile, [''])
+test('T10390', normal, compile, [''])