Fix diamond graphs

src/graph.luau

@@ -181,47 +181,80 @@ local function evaluate_node<T>(node: Node<T>)
     return cur_value ~= new_value -- node has changed value
 end
 
-local function update_from<T>(node: StartNode<T>, n0: number)
-    if not node[1] then return end
+-- local function update_from<T>(node: StartNode<T>, n0: number)
+--     if not node[1] then return end
 
-    local n = n0
+--     local n = n0
 
-    -- unparent all children and queue for eval
-    do
-        local child = node[1]
-        while child do
-            --assert(child.parents.owner)
-            unparent(child)
-            n += 1
-            update_queue[n] = child
-            child = node[1]
-        end
+--     -- unparent all children and queue for eval
+--     do
+--         local child = node[1]
+--         while child do
+--             --assert(child.parents.owner)
+--             unparent(child)
+--             n += 1
+--             update_queue[n] = child
+--             child = node[1]
+--         end
+--     end
+
+--     update_queue.n = n
+
+--     -- evaluate all queued children
+--     for i = n0 + 1, n do
+--         local child = update_queue[i]
+--         assert(type(child.effect) == "function")
+
+--         if evaluate_node(child) then
+--             update_from(child, n)
+--         end
+
+--         update_queue[i] = false :: any -- false instead of nil to avoid sparse
+--     end
+
+--     update_queue.n = n0
+-- end
+
+-- local function update<T>(node: StartNode<T>)
+--     update_from(node, update_queue.n)
+-- end
+
+local function queue_children<T>(node: StartNode<T>)
+    local i = update_queue.n
+    local child = node[1]
+    while child do
+        --assert(child.parents.owner)
+        unparent(child)
+        i += 1
+        update_queue[i] = child
+        child = node[1]
     end
+    update_queue.n = i
+end
 
-    update_queue.n = n
+local function update<T>(root: StartNode<T>)
+    local n0 = update_queue.n
+    queue_children(root)
 
-    -- evaluate all queued children
-    for i = n0 + 1, n do
-        local child = update_queue[i]
-        assert(type(child.effect) == "function")
+    local i = n0 + 1
+    while i <= update_queue.n do
+        local node = update_queue[i]
+        assert(node.effect)
 
-        if evaluate_node(child) then
-            update_from(child, n)
+        if evaluate_node(node) then
+            queue_children(node)
         end
 
         update_queue[i] = false :: any -- false instead of nil to avoid sparse
+        i += 1
     end
 
     update_queue.n = n0
 end
 
-local function update<T>(node: StartNode<T>)
-    update_from(node, update_queue.n)
-end
-
 local function track<T>(node: StartNode<T>)
     local scope = get_scope()
-    if scope and type(scope.effect) == "function" then -- do not track nodes with no effect
+    if scope and scope.effect then -- do not track nodes with no effect
         add_child(node, scope)
     end
 end