Fix temp variable handling for the super() class cell. (GH-3289)

Closes GH-3246.

Cython/Compiler/ExprNodes.py

@@ -9136,9 +9136,8 @@ class ClassCellInjectorNode(ExprNode):
     def analyse_expressions(self, env):
         return self
 
-    def generate_evaluation_code(self, code):
-        if self.is_active:
-            self.allocate_temp_result(code)
+    def generate_result_code(self, code):
+        assert self.is_active
         code.putln(
             '%s = PyList_New(0); %s' % (
                 self.result(),
@@ -9146,7 +9145,7 @@ class ClassCellInjectorNode(ExprNode):
         code.put_gotref(self.result())
 
     def generate_injection_code(self, code, classobj_cname):
-        if self.is_active:
+        assert self.is_active
         code.globalstate.use_utility_code(
             UtilityCode.load_cached("CyFunctionClassCell", "CythonFunction.c"))
         code.put_error_if_neg(self.pos, '__Pyx_CyFunction_InitClassCell(%s, %s)' % (

Cython/Compiler/Nodes.py

@@ -4596,12 +4596,22 @@ class PyClassDefNode(ClassDefNode):
             self.metaclass.generate_evaluation_code(code)
         self.dict.generate_evaluation_code(code)
         cenv.namespace_cname = cenv.class_obj_cname = self.dict.result()
-        self.class_cell.generate_evaluation_code(code)
+
+        class_cell = self.class_cell
+        if class_cell is not None and not class_cell.is_active:
+            class_cell = None
+
+        if class_cell is not None:
+            class_cell.generate_evaluation_code(code)
         self.body.generate_execution_code(code)
         self.class_result.generate_evaluation_code(code)
-        self.class_cell.generate_injection_code(
+        if class_cell is not None:
+            class_cell.generate_injection_code(
                 code, self.class_result.result())
-        self.class_cell.generate_disposal_code(code)
+        if class_cell is not None:
+            class_cell.generate_disposal_code(code)
+            class_cell.free_temps(code)
+
         cenv.namespace_cname = cenv.class_obj_cname = self.classobj.result()
         self.target.generate_assignment_code(self.class_result, code)
         self.dict.generate_disposal_code(code)

tests/run/py3k_super.pyx

 # mode: run
-# tag: py3k_super
+# tag: py3k_super, gh3246
 
 class A(object):
     def method(self):
@@ -89,3 +89,21 @@ cdef class CClassSub(CClassBase):
 #         return super().method_cp()
 #     cdef method_c(self):
 #         return super().method_c()
+
+
+def freeing_class_cell_temp_gh3246():
+    # https://github.com/cython/cython/issues/3246
+    """
+    >>> abc = freeing_class_cell_temp_gh3246()
+    >>> abc().a
+    1
+    """
+    class SimpleBase(object):
+        def __init__(self):
+            self.a = 1
+
+    class ABC(SimpleBase):
+        def __init__(self):
+            super().__init__()
+
+    return ABC