syntax_data: {"ast_node_type":"function","tokens":[{"end":96,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet: fn update_disambiguator(expn_data: &mut ExpnData, mut ctx: impl HashStableContext) -> ExpnHash {
context_before: /// collisions are only possible between `ExpnId`s within the same crate.
context_after:     // This disambiguator should not have been set yet.