syntax_data: {"ast_node_type":"import","tokens":[{"end":75,"kind":"keyword","start":0,"text":"//!"}]}
source_snippet: //! - `as_rvalue` -- yields an `Rvalue`, suitable for use in an assignment;
context_before: //!   except it always returns a fresh place, even for constants
context_after: //!   as of this writing, never needed outside of the `expr` module itself