Merge reactive scope refactor

src/derive.luau

@@ -1,15 +1,28 @@
 if not game then script = require "test/relative-string" end
 
+local throw = require(script.Parent.throw)
 local graph = require(script.Parent.graph)
-local create = graph.create
-local capture_and_link = graph.capture_and_link
+local create_node = graph.create_node
+local set_owner = graph.set_owner
+local track = graph.track
+local get_scope = graph.get_scope
+local evaluate_node = graph.evaluate_node
 
-local function derive<T>(fn: () -> T): () -> T
-    local node, read_node_value = create((false :: any) :: T)
+local function derive<T>(source: () -> T): () -> T
+    local owner = get_scope()
+    if not owner then
+        throw("cannot derive in non-reactive scope")
+    end; assert(owner)
 
-    node.cache = capture_and_link(node, fn)
+    local node = create_node(false :: any, source)
 
-    return read_node_value
+    set_owner(node, owner)
+    evaluate_node(node)
+
+    return function()
+        track(node)
+        return node.cache
+    end
 end
 
 return derive