syntax_data: {"ast_node_type":"other","tokens":[{"end":38,"kind":"keyword","start":0,"text":"user_ty:"}]}
source_snippet:                         user_ty: None,
context_before:                         fields: Box::new([FieldExpr { name: FieldIdx::from(0u32), expr }]),
context_after:                         base: AdtExprBase::None,