syntax_data: {"ast_node_type":"impl","tokens":[{"end":74,"kind":"keyword","start":0,"text":"print_value:"}]}
source_snippet:         print_value: impl FnOnce(&mut Self, &T) -> Result<(), PrintError>,
context_before:         value: &ty::Binder<'tcx, T>,
context_after:     ) -> Result<(), PrintError>