Initial commit of Python queries and QL libraries.

python/ql/src/Classes/InconsistentMRO.ql

@@ -0,0 +1,27 @@
+/**
+ * @name Inconsistent method resolution order
+ * @description Class definition will raise a type error at runtime due to inconsistent method resolution order(MRO)
+ * @kind problem
+ * @tags reliability
+ *       correctness
+ * @problem.severity error
+ * @sub-severity high
+ * @precision very-high
+ * @id py/inconsistent-mro
+ */
+
+import python
+
+ClassObject left_base(ClassObject type, ClassObject base) {
+    exists(int i | i > 0 and type.getBaseType(i) = base and result = type.getBaseType(i-1))
+}
+
+predicate invalid_mro(ClassObject t, ClassObject left, ClassObject right) {
+    t.isNewStyle() and
+    left = left_base(t, right) and left = right.getAnImproperSuperType()
+}
+
+from ClassObject t, ClassObject left, ClassObject right
+where invalid_mro(t, left, right)
+select t, "Construction of class " + t.getName() + " can fail due to invalid method resolution order(MRO) for bases $@ and $@.",
+left, left.getName(), right, right.getName()