syntax_data: {"ast_node_type":"other","tokens":[{"end":69,"kind":"keyword","start":0,"text":"//!"}]}
source_snippet: //! `as_constant`. This creates a `Constant<H>`, but naturally it can
context_before: //! Finally, if it's a constant you seek, then call
context_after: //! only be used on constant expressions and hence is needed only in