Disallow explicitly locking a global cypclass variable and add associated unit tests

Cython/Compiler/CypclassTransforms.py

@@ -595,6 +595,9 @@ class CypclassLockTransform(Visitor.EnvTransform):
         if not node.obj.type.is_cyp_class:
             error(node.obj.pos, "Locking non-cypclass reference")
             return node
+        if not obj_ref_id.is_local or obj_ref_id.is_arg:
+            error(node.obj.pos, "Can only lock local variables or arguments")
+            return node
         with self.stacklock(obj_ref_id, node.state):
             self.visit(node.body)
         return node

tests/errors/cypclass_lock_error.pyx

@@ -25,6 +25,13 @@ def incorrect_locks():
     obj.a
     take_read_locked(obj)
 
+
+cdef A global_cyobject
+
+cdef void global_lock_taking():
+    with wlocked global_cyobject:
+        global_cyobject.setter(global_cyobject.getter() + 1)
+
 _ERRORS = u"""
 20:4: Reference 'obj' is not correctly locked in this expression (write lock required)
 21:4: Reference 'obj' is not correctly locked in this expression (read lock required)
@@ -32,4 +39,5 @@ _ERRORS = u"""
 24:26: Reference 'obj' is not correctly locked in this expression (write lock required)
 25:4: Reference 'obj' is not correctly locked in this expression (read lock required)
 26:21: Reference 'obj' is not correctly locked in this expression (read lock required)
+32:17: Can only lock local variables or arguments
 """

tests/run/cypclass_lock.pyx

@@ -35,29 +35,6 @@ def test_argument_recursivity(n):
         argument_recursivity(obj, n)
         print obj.a
 
-cdef A global_cyobject
-
-cdef init_global_cyobject():
-    global global_cyobject
-    global_cyobject = A()
-
-cdef void recursive_lock_taking(int arg):
-    global global_cyobject
-    if arg > 0:
-        with wlocked global_cyobject:
-            global_cyobject.setter(global_cyobject.getter() + 1)
-            recursive_lock_taking(arg - 1)
-
-def test_recursive_side_effect_locking(n):
-    """
-    >>> test_recursive_side_effect_locking(42)
-    42
-    """
-    init_global_cyobject()
-    recursive_lock_taking(42)
-    with rlocked global_cyobject:
-        print global_cyobject.getter()
-
 cdef cypclass Container:
     A object
     __init__(self):