[commit: ghc] master: Some stress tests for the empty case linter (6cf0c79)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/6cf0c7962c582eefb84cdf2735504d034fb16314/ghc

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

commit 6cf0c7962c582eefb84cdf2735504d034fb16314
Author: Joachim Breitner <mail at joachim-breitner.de>
Date:   Tue Mar 24 11:28:55 2015 +0100

    Some stress tests for the empty case linter
    
    This is a variation of T2431 where the emptyness of the type is hidden
    behind a newtype, a type family and a closed type family. In all cases,
    it would be sound for the compiler to determine that the equality type
    is empty and the case alternatives may be dropped.
    
    At the moment, GHC does _not_ determine that. But if it ever does, this
    test ensures that we do not forget to make the lint from #10180 smarter
    as well.


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

6cf0c7962c582eefb84cdf2735504d034fb16314
 testsuite/tests/simplCore/should_compile/T10180.hs | 27 ++++++++++++++++++++++
 testsuite/tests/simplCore/should_compile/all.T     |  1 +
 2 files changed, 28 insertions(+)

diff --git a/testsuite/tests/simplCore/should_compile/T10180.hs b/testsuite/tests/simplCore/should_compile/T10180.hs
new file mode 100644
index 0000000..55c52f0
--- /dev/null
+++ b/testsuite/tests/simplCore/should_compile/T10180.hs
@@ -0,0 +1,27 @@
+{-# LANGUAGE TypeOperators, TypeFamilies, GADTs, EmptyCase #-}
+module T10180 where
+
+newtype Foo = Foo Int
+
+type family Bar a
+type instance Bar Int = Int
+
+type family Baz a where
+  Baz Int = Int
+  Baz Char = Int
+
+data a :~: b where
+  Refl :: a :~: a
+
+absurd0 :: Int :~: Bool -> a
+absurd0 x = case x of {}
+
+absurd1 :: Foo :~: Bool -> a
+absurd1 x = case x of {}
+
+absurd2 :: Bar Int :~: Bool -> a
+absurd2 x = case x of {}
+
+absurd3 :: Baz a :~: Bool -> a
+absurd3 x = case x of {}
+
diff --git a/testsuite/tests/simplCore/should_compile/all.T b/testsuite/tests/simplCore/should_compile/all.T
index 6c000d3..daf038a 100644
--- a/testsuite/tests/simplCore/should_compile/all.T
+++ b/testsuite/tests/simplCore/should_compile/all.T
@@ -212,3 +212,4 @@ test('T9583', only_ways(['optasm']), compile, [''])
 test('T9565', only_ways(['optasm']), compile, [''])
 test('T5821', only_ways(['optasm']), compile, [''])
 test('T10176', only_ways(['optasm']), compile, [''])
+test('T10180', only_ways(['optasm']), compile, [''])