Correctly check recursive constraints involving type parameters. Fixes #8232

1 files changed, 37 insertions, 0 deletions

diff --git a/mcs/tests/gtest-571.cs b/mcs/tests/gtest-571.cs
new file mode 100644
index 00000000000..75cd9a2a828
--- /dev/null
+++ b/mcs/tests/gtest-571.cs
@@ -0,0 +1,37 @@
+using System;
+
+public abstract class A<T>
+{
+	public abstract A<MM> For<MM> () where MM : T;
+}
+
+public class B<U, X, V> : A<V>
+	where V : X
+	where X : U
+{
+	readonly A<U> _inner;
+
+	public B (A<U> inner)
+	{
+		_inner = inner;
+	}
+
+	public override A<PP> For<PP> () // base constraint is copied as PP : V
+	{
+		return _inner.For<PP> ();
+	}
+}
+
+public class Test : A<Test>
+{
+	public static void Main ()
+	{
+		var t = new Test ();
+		new B<Test, Test, Test> (t).For<Test> ();
+	}
+
+	public override A<QQ> For<QQ> ()
+	{
+		return null;
+	}
+}