syntax_data: {"ast_node_type":"function","tokens":[{"end":90,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                 // `trait Fn { fn call_once(&self) { .. } }`. This is mostly for extension
context_before:                 // FIXME: This doesn't check for malformed libcore that defines, e.g.,
context_after:                 // methods.