syntax_data: {"ast_node_type":"other","tokens":[{"end":70,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// Compile `expr`, yielding a compile-time constant. Assumes that
context_before: impl<'a, 'tcx> Builder<'a, 'tcx> {
context_after:     /// `expr` is a valid compile-time constant!