syntax_data: {"ast_node_type":"other","tokens":[{"end":7,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     ///
context_before:     /// compiling `rustc` will be used instead (or llvm if it is not set).
context_after:     /// N.B. when *using* the compiler, backend can always be overridden with `-Zcodegen-backend`.