syntax_data: {"ast_node_type":"other","tokens":[{"end":18,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                 //
context_before:                 // allocates the correct number of elements once up-front [1].
context_after:                 // [1] https://doc.rust-lang.org/1.85.0/src/alloc/vec/spec_from_iter_nested.rs.html#47