{"ast_node_type":"function","tokens":[{"end":75,"kind":"keyword","start":0,"text":"fn"}]}
                fn fn_ctr2() fn() -> Result<Foo<T>, u32> [type_could_unify]
                fn fn_ctr() fn() -> Option<Foo<T>> [type_could_unify]
                me fn_no_ret(…) fn(&self) [type_could_unify]