Python: Adds preliminary modernization

Author: BekaValentine

python/ql/src/Functions/IterReturnsNonSelf.ql

@@ -12,8 +12,8 @@
 
 import python
 
-Function iter_method(ClassObject t) {
-		result = ((FunctionObject)t.lookupAttribute("__iter__")).getFunction()
+Function iter_method(ClassValue t) {
+		result = ((FunctionValue)t.lookup("__iter__")).getScope()
 }
 
 predicate is_self(Name value, Function f) {
@@ -28,6 +28,6 @@ predicate returns_non_self(Function f) {
 		exists(Return r | r.getScope() = f and not exists(r.getValue()))
 }
 
-from ClassObject t, Function iter
+from ClassValue t, Function iter
 where t.isIterator() and iter = iter_method(t) and returns_non_self(iter)
 select t, "Class " + t.getName() + " is an iterator but its $@ method does not return 'self'.", iter, iter.getName()

python/ql/src/semmle/python/objects/ObjectAPI.qll

@@ -374,7 +374,7 @@ class CallableValue extends Value {
 
 /** Class representing classes in the Python program, both Python and built-in.
  */
-class ClassValue extends Value {
+class   ClassValue extends Value {
 
     ClassValue() {
         this.(ObjectInternal).isClass() = true
@@ -413,6 +413,26 @@ class ClassValue extends Value {
         this.hasAttribute("__getitem__")
     }
 
+    /** Holds if this class is an iterator. */
+    predicate isIterator() {
+        this.hasAttribute("__iter__") and 
+        (major_version() = 3 and this.hasAttribute("__next__")
+         or   
+         /* Because 'next' is a common method name we need to check that an __iter__
+          * method actually returns this class. This is not needed for Py3 as the
+          * '__next__' method exists to define a class as an iterator.
+          */
+         major_version() = 2 and this.hasAttribute("next") and 
+         exists(ClassObject other, FunctionObject iter | 
+            other.declaredAttribute("__iter__") = iter |
+            iter.getAnInferredReturnType() = this
+         )
+        )
+        or
+        /* This will be redundant when we have C class information */
+        this = ClassValue::generator()
+    }
+
     /** Holds if this class is a descriptor. */
     predicate isDescriptorType() {
         this.hasAttribute("__get__")