syntax_data: {"ast_node_type":"other","tokens":[{"end":22,"kind":"keyword","start":0,"text":"expr:"}]}
source_snippet:     expr: &Expr<'tcx>,
context_before: pub(crate) fn as_constant_inner<'tcx>(
context_after:     push_cuta: impl FnMut(&Box<CanonicalUserType<'tcx>>) -> Option<UserTypeAnnotationIndex>,