Added test for MRO in complicated diamond hierarchy (PY-4183)

python/testData/codeInsight/classMRO/ComplicatedDiamond.py

@@ -0,0 +1,30 @@
+class A(object):
+    pass
+
+
+class B(A):
+    pass
+
+
+class C(A):
+    pass
+
+
+class D(A):
+    pass
+
+
+class E(B):
+    pass
+
+
+class F(B):
+    pass
+
+
+class G(C, D):
+    pass
+
+
+class H(E, F, G):
+    pass

python/testSrc/com/jetbrains/python/codeInsight/PyClassMROTest.java

@@ -47,6 +47,11 @@ public class PyClassMROTest extends PyTestCase {
     assertMRO(getClass("G"), "E", "F", "object");
   }
 
+  // PY-4183
+  public void testComplicatedDiamond() {
+    assertMRO(getClass("H"), "E", "F", "B", "G", "C", "D", "A", "object");
+  }
+
   public void assertMRO(@NotNull PyClass cls, @NotNull String... mro) {
     final List<PyClassLikeType> types = cls.getAncestorTypes(TypeEvalContext.fastStubOnly(null));
     final List<String> classNames = new ArrayList<String>();