syntax_data: {"ast_node_type":"other","tokens":[{"end":72,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // allocating a new `Arc` and cloning the `T` only if required).
context_before:         // the contained type, which `Arc::make_mut` will accomplish (by
context_after:         // This is done *before* casting to `Arc<ManuallyDrop<T>>` so that