syntax_data: {"ast_node_type":"other","tokens":[{"end":63,"kind":"keyword","start":0,"text":"//!"}]}
source_snippet: //! generates an error giving, respectively, the symbol name or
context_before: //! either a `rustc_symbol_name` or `rustc_def_path` attribute and
context_after: //! def-path. This is used for unit testing the code that generates