Use temporaries to prevent nested cypclass lock acquisition

Cython/Compiler/CypclassTransforms.py

@@ -445,10 +445,12 @@ class CypclassLockTransform(Visitor.EnvTransform):
                 error(lock.pos, "A writelock is required, but a readlock is manually acquired")
             return obj
         except:
+            self.autolocks += 1
             return ExprNodes.CoerceToLockedNode(obj, self.current_env(), rlock_only = not exclusive)
 
     def __call__(self, root):
         self.locked = {}
+        self.autolocks = 0
         return super(CypclassLockTransform, self).__call__(root)
 
     def visit_Node(self, node):
@@ -495,6 +497,21 @@ class CypclassLockTransform(Visitor.EnvTransform):
                 node.obj = self.lock(node.obj, exclusive=node.is_target)
         return node
 
+    def visit_value(self, node):
+        if node is None:
+            return None
+        autolocks = self.autolocks
+        node = self.visit(node)
+        if self.autolocks > autolocks:
+            self.autolocks = 0
+            return node.coerce_to_temp(self.current_env())
+        return node
+
+    def visit_IndexNode(self, node):
+        node.index = self.visit_value(node.index)
+        node.base = self.visit(node.base)
+        return node
+
     def visit_DelStatNode(self, node):
         for arg in node.args:
             arg_entry = self.id(arg)
@@ -511,7 +528,8 @@ class CypclassLockTransform(Visitor.EnvTransform):
             # Disallow re-binding a locked name
             error(lhs.pos, "Assigning to a locked cypclass reference")
             return node
-        self.visitchildren(node)
+        node.rhs = self.visit_value(node.rhs)
+        self.visitchildren(node, exclude=['rhs'])
         return node
 
     def visit_CascadedAssignmentNode(self, node):
@@ -520,7 +538,8 @@ class CypclassLockTransform(Visitor.EnvTransform):
                 # Disallow re-binding a locked name
                 error(lhs.pos, "Assigning to a locked cypclass reference")
                 return node
-        self.visitchildren(node)
+        node.rhs = self.visit_value(node.rhs)
+        self.visitchildren(node, exclude=['rhs'])
         return node
 
     def visit_WithTargetAssignmentStatNode(self, node):