[project @ 2005-10-12 13:34:59 by simonpj]

Add a test for the unifyTyConApp bug

testsuite/tests/ghc-regress/gadt/all.T

@@ -9,6 +9,7 @@ test('gadt5', normal, compile_and_run, [''])
 test('gadt6', normal, compile, [''])
 test('gadt7', normal, compile_fail, [''])
 test('gadt8', normal, compile, [''])
+test('gadt9', normal, compile, [''])
 test('gadt10', normal, compile_fail, [''])
 test('gadt11', normal, compile_fail, [''])
 test('red-black', normal, compile, [''])

testsuite/tests/ghc-regress/gadt/gadt9.hs

+{-# OPTIONS -fglasgow-exts #-}
+
+-- This one requires careful handling in 
+-- TcUnify.unifyTyConApp, to preserve rigidity.
+
+module ShouldCompile where
+
+data X a b where
+    X :: X a a
+
+data Y x a b where
+    Y :: x a b -> x b c -> Y x a c
+
+doy :: Y X a b -> Y X a b
+doy (Y X X) = Y X X