Add sibling()

src/sibling.luau

@@ -0,0 +1,32 @@
+if not game then script = require "test/relative-string" end
+
+local graph = require(script.Parent.graph)
+type Node<T> = graph.Node<T>
+
+export type Source<T> = (() -> T) & ((value: T) -> T)
+
+local function sibling<T>(fn: () -> T): (() -> (), T)
+    local node = graph.get_scope()
+    if not node then error("") end
+
+    local parent_node = node.owner
+    if not parent_node then error("") end
+
+    local sibling = graph.create_node(parent_node :: Node<unknown>, false, false)
+
+    graph.push_scope(sibling)
+
+    local ok, result = pcall(fn)
+
+    graph.pop_scope()
+
+    if not ok then error(result, 0) end
+
+    local function destroy()
+        graph.destroy(sibling)
+    end
+
+    return destroy, result
+end
+
+return sibling :: (<T>(fn: () -> T) -> (() -> (), T)) & ((fn: () -> ()) -> () -> ())