syntax_data: {"ast_node_type":"function","tokens":[{"end":86,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     ///         pub fn f() {} // `f`'s `SyntaxContext` has a single `ExpnId` from `m`.
context_before:     ///     mod foo {
context_after:     ///         pub fn $i() {} // `$i`'s `SyntaxContext` is empty.