Resolve unexpected_cfgs warning

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:253:13
        |
    253 | #![cfg_attr(doc_cfg, feature(doc_cfg))]
        |             ^^^^^^^
        |
        = help: expected names are: `clippy`, `debug_assertions`, `doc`, `docsrs`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, `windows`
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: `#[warn(unexpected_cfgs)]` on by default

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:320:12
        |
    320 | #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:326:12
        |
    326 | #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:336:12
        |
    336 | #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:342:12
        |
    342 | #[cfg_attr(doc_cfg, doc(cfg(feature = "derive")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:353:12
        |
    353 | #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:356:12
        |
    356 | #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:362:12
        |
    362 | #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:371:12
        |
    371 | #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:377:12
        |
    377 | #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:383:12
        |
    383 | #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:391:5
        |
    391 |     doc_cfg,
        |     ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:403:12
        |
    403 | #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:431:12
        |
    431 | #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:436:5
        |
    436 |     doc_cfg,
        |     ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:444:12
        |
    444 | #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:448:12
        |
    448 | #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:460:12
        |
    460 | #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:469:12
        |
    469 | #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:483:12
        |
    483 | #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:491:12
        |
    491 | #[cfg_attr(doc_cfg, doc(cfg(all(feature = "parsing", feature = "printing"))))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:497:12
        |
    497 | #[cfg_attr(doc_cfg, doc(cfg(feature = "full")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:508:12
        |
    508 | #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:842:12
        |
    842 | #[cfg_attr(doc_cfg, doc(cfg(feature = "fold")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:846:12
        |
    846 | #[cfg_attr(doc_cfg, doc(cfg(feature = "visit")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:850:12
        |
    850 | #[cfg_attr(doc_cfg, doc(cfg(feature = "visit-mut")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:897:12
        |
    897 | #[cfg_attr(doc_cfg, doc(cfg(all(feature = "parsing", feature = "proc-macro"))))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:915:12
        |
    915 | #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:942:12
        |
    942 | #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/lib.rs:982:12
        |
    982 | #[cfg_attr(doc_cfg, doc(cfg(all(feature = "parsing", feature = "full"))))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/group.rs:145:12
        |
    145 | #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/group.rs:223:12
        |
    223 | #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/group.rs:278:12
        |
    278 | #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:571:12
        |
    571 | #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:579:12
        |
    579 | #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:640:12
        |
    640 | #[cfg_attr(doc_cfg, doc(cfg(feature = "clone-impls")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:644:12
        |
    644 | #[cfg_attr(doc_cfg, doc(cfg(feature = "clone-impls")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:652:12
        |
    652 | #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:660:12
        |
    660 | #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:664:12
        |
    664 | #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:672:12
        |
    672 | #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |            ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:404:24
        |
    404 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "clone-impls")))]
        |                          ^^^^^^^
    ...
    566 | / define_punctuation_structs! {
    567 | |     "_" pub struct Underscore/1 /// wildcard patterns, inferred types, unnamed items in constants, extern c...
    568 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:408:24
        |
    408 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "clone-impls")))]
        |                          ^^^^^^^
    ...
    566 | / define_punctuation_structs! {
    567 | |     "_" pub struct Underscore/1 /// wildcard patterns, inferred types, unnamed items in constants, extern c...
    568 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:416:24
        |
    416 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    566 | / define_punctuation_structs! {
    567 | |     "_" pub struct Underscore/1 /// wildcard patterns, inferred types, unnamed items in constants, extern c...
    568 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:424:24
        |
    424 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    566 | / define_punctuation_structs! {
    567 | |     "_" pub struct Underscore/1 /// wildcard patterns, inferred types, unnamed items in constants, extern c...
    568 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:428:24
        |
    428 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    566 | / define_punctuation_structs! {
    567 | |     "_" pub struct Underscore/1 /// wildcard patterns, inferred types, unnamed items in constants, extern c...
    568 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:436:24
        |
    436 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    566 | / define_punctuation_structs! {
    567 | |     "_" pub struct Underscore/1 /// wildcard patterns, inferred types, unnamed items in constants, extern c...
    568 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:277:24
        |
    277 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "clone-impls")))]
        |                          ^^^^^^^
    ...
    736 | / define_keywords! {
    737 | |     "abstract"    pub struct Abstract
    738 | |     "as"          pub struct As
    739 | |     "async"       pub struct Async
    ...   |
    788 | |     "yield"       pub struct Yield
    789 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_keywords` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:281:24
        |
    281 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "clone-impls")))]
        |                          ^^^^^^^
    ...
    736 | / define_keywords! {
    737 | |     "abstract"    pub struct Abstract
    738 | |     "as"          pub struct As
    739 | |     "async"       pub struct Async
    ...   |
    788 | |     "yield"       pub struct Yield
    789 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_keywords` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:289:24
        |
    289 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    736 | / define_keywords! {
    737 | |     "abstract"    pub struct Abstract
    738 | |     "as"          pub struct As
    739 | |     "async"       pub struct Async
    ...   |
    788 | |     "yield"       pub struct Yield
    789 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_keywords` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:297:24
        |
    297 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    736 | / define_keywords! {
    737 | |     "abstract"    pub struct Abstract
    738 | |     "as"          pub struct As
    739 | |     "async"       pub struct Async
    ...   |
    788 | |     "yield"       pub struct Yield
    789 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_keywords` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:301:24
        |
    301 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    736 | / define_keywords! {
    737 | |     "abstract"    pub struct Abstract
    738 | |     "as"          pub struct As
    739 | |     "async"       pub struct Async
    ...   |
    788 | |     "yield"       pub struct Yield
    789 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_keywords` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:309:24
        |
    309 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    736 | / define_keywords! {
    737 | |     "abstract"    pub struct Abstract
    738 | |     "as"          pub struct As
    739 | |     "async"       pub struct Async
    ...   |
    788 | |     "yield"       pub struct Yield
    789 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_keywords` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:315:24
        |
    315 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
        |                          ^^^^^^^
    ...
    736 | / define_keywords! {
    737 | |     "abstract"    pub struct Abstract
    738 | |     "as"          pub struct As
    739 | |     "async"       pub struct Async
    ...   |
    788 | |     "yield"       pub struct Yield
    789 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_keywords` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:323:24
        |
    323 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                          ^^^^^^^
    ...
    736 | / define_keywords! {
    737 | |     "abstract"    pub struct Abstract
    738 | |     "as"          pub struct As
    739 | |     "async"       pub struct Async
    ...   |
    788 | |     "yield"       pub struct Yield
    789 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_keywords` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:454:24
        |
    454 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
        |                          ^^^^^^^
    ...
    791 | / define_punctuation! {
    792 | |     "&"           pub struct And/1        /// bitwise and logical AND, borrow, references, reference patterns
    793 | |     "&&"          pub struct AndAnd/2     /// lazy AND, borrow, references, reference patterns
    794 | |     "&="          pub struct AndEq/2      /// bitwise AND assignment
    ...   |
    837 | |     "~"           pub struct Tilde/1      /// unused since before Rust 1.0
    838 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:462:24
        |
    462 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                          ^^^^^^^
    ...
    791 | / define_punctuation! {
    792 | |     "&"           pub struct And/1        /// bitwise and logical AND, borrow, references, reference patterns
    793 | |     "&&"          pub struct AndAnd/2     /// lazy AND, borrow, references, reference patterns
    794 | |     "&="          pub struct AndEq/2      /// bitwise AND assignment
    ...   |
    837 | |     "~"           pub struct Tilde/1      /// unused since before Rust 1.0
    838 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:404:24
        |
    404 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "clone-impls")))]
        |                          ^^^^^^^
    ...
    791 | / define_punctuation! {
    792 | |     "&"           pub struct And/1        /// bitwise and logical AND, borrow, references, reference patterns
    793 | |     "&&"          pub struct AndAnd/2     /// lazy AND, borrow, references, reference patterns
    794 | |     "&="          pub struct AndEq/2      /// bitwise AND assignment
    ...   |
    837 | |     "~"           pub struct Tilde/1      /// unused since before Rust 1.0
    838 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation_structs` which comes from the expansion of the macro `define_punctuation` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:408:24
        |
    408 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "clone-impls")))]
        |                          ^^^^^^^
    ...
    791 | / define_punctuation! {
    792 | |     "&"           pub struct And/1        /// bitwise and logical AND, borrow, references, reference patterns
    793 | |     "&&"          pub struct AndAnd/2     /// lazy AND, borrow, references, reference patterns
    794 | |     "&="          pub struct AndEq/2      /// bitwise AND assignment
    ...   |
    837 | |     "~"           pub struct Tilde/1      /// unused since before Rust 1.0
    838 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation_structs` which comes from the expansion of the macro `define_punctuation` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:416:24
        |
    416 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    791 | / define_punctuation! {
    792 | |     "&"           pub struct And/1        /// bitwise and logical AND, borrow, references, reference patterns
    793 | |     "&&"          pub struct AndAnd/2     /// lazy AND, borrow, references, reference patterns
    794 | |     "&="          pub struct AndEq/2      /// bitwise AND assignment
    ...   |
    837 | |     "~"           pub struct Tilde/1      /// unused since before Rust 1.0
    838 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation_structs` which comes from the expansion of the macro `define_punctuation` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:424:24
        |
    424 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    791 | / define_punctuation! {
    792 | |     "&"           pub struct And/1        /// bitwise and logical AND, borrow, references, reference patterns
    793 | |     "&&"          pub struct AndAnd/2     /// lazy AND, borrow, references, reference patterns
    794 | |     "&="          pub struct AndEq/2      /// bitwise AND assignment
    ...   |
    837 | |     "~"           pub struct Tilde/1      /// unused since before Rust 1.0
    838 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation_structs` which comes from the expansion of the macro `define_punctuation` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:428:24
        |
    428 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    791 | / define_punctuation! {
    792 | |     "&"           pub struct And/1        /// bitwise and logical AND, borrow, references, reference patterns
    793 | |     "&&"          pub struct AndAnd/2     /// lazy AND, borrow, references, reference patterns
    794 | |     "&="          pub struct AndEq/2      /// bitwise AND assignment
    ...   |
    837 | |     "~"           pub struct Tilde/1      /// unused since before Rust 1.0
    838 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation_structs` which comes from the expansion of the macro `define_punctuation` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:436:24
        |
    436 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    791 | / define_punctuation! {
    792 | |     "&"           pub struct And/1        /// bitwise and logical AND, borrow, references, reference patterns
    793 | |     "&&"          pub struct AndAnd/2     /// lazy AND, borrow, references, reference patterns
    794 | |     "&="          pub struct AndEq/2      /// bitwise AND assignment
    ...   |
    837 | |     "~"           pub struct Tilde/1      /// unused since before Rust 1.0
    838 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_punctuation_structs` which comes from the expansion of the macro `define_punctuation` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:511:24
        |
    511 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "clone-impls")))]
        |                          ^^^^^^^
    ...
    840 | / define_delimiters! {
    841 | |     Brace         pub struct Brace        /// `{`&hellip;`}`
    842 | |     Bracket       pub struct Bracket      /// `[`&hellip;`]`
    843 | |     Parenthesis   pub struct Paren        /// `(`&hellip;`)`
    844 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_delimiters` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:515:24
        |
    515 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "clone-impls")))]
        |                          ^^^^^^^
    ...
    840 | / define_delimiters! {
    841 | |     Brace         pub struct Brace        /// `{`&hellip;`}`
    842 | |     Bracket       pub struct Bracket      /// `[`&hellip;`]`
    843 | |     Parenthesis   pub struct Paren        /// `(`&hellip;`)`
    844 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_delimiters` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:523:24
        |
    523 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    840 | / define_delimiters! {
    841 | |     Brace         pub struct Brace        /// `{`&hellip;`}`
    842 | |     Bracket       pub struct Bracket      /// `[`&hellip;`]`
    843 | |     Parenthesis   pub struct Paren        /// `(`&hellip;`)`
    844 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_delimiters` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:531:24
        |
    531 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    840 | / define_delimiters! {
    841 | |     Brace         pub struct Brace        /// `{`&hellip;`}`
    842 | |     Bracket       pub struct Bracket      /// `[`&hellip;`]`
    843 | |     Parenthesis   pub struct Paren        /// `(`&hellip;`)`
    844 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_delimiters` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:535:24
        |
    535 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    840 | / define_delimiters! {
    841 | |     Brace         pub struct Brace        /// `{`&hellip;`}`
    842 | |     Bracket       pub struct Bracket      /// `[`&hellip;`]`
    843 | |     Parenthesis   pub struct Paren        /// `(`&hellip;`)`
    844 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_delimiters` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/token.rs:543:24
        |
    543 |               #[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
        |                          ^^^^^^^
    ...
    840 | / define_delimiters! {
    841 | |     Brace         pub struct Brace        /// `{`&hellip;`}`
    842 | |     Bracket       pub struct Bracket      /// `[`&hellip;`]`
    843 | |     Parenthesis   pub struct Paren        /// `(`&hellip;`)`
    844 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `define_delimiters` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:172:16
        |
    172 |     #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:444:16
        |
    444 |     #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:472:16
        |
    472 |     #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/macros.rs:140:20
        |
    140 |           #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
        |                      ^^^^^^^
        |
       ::: src/attr.rs:451:1
        |
    451 | / ast_enum_of_structs! {
    452 | |     /// Content of a compile-time structured attribute.
    453 | |     ///
    454 | |     /// ## Path
    ...   |
    481 | |     }
    482 | | }
        | |_- in this macro invocation
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
        = note: this warning originates in the macro `generate_to_tokens` which comes from the expansion of the macro `ast_enum_of_structs` (in Nightly builds, run with -Z macro-backtrace for more info)

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:486:16
        |
    486 |     #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:496:16
        |
    496 |     #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:221:16
        |
    221 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:244:16
        |
    244 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:390:16
        |
    390 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:405:16
        |
    405 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:421:16
        |
    421 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:519:16
        |
    519 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:531:16
        |
    531 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:549:16
        |
    549 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:569:16
        |
    569 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:576:16
        |
    576 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:584:16
        |
    584 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:667:16
        |
    667 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:675:16
        |
    675 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:683:16
        |
    683 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:764:16
        |
    764 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:777:16
        |
    777 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/attr.rs:785:16
        |
    785 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
        |                ^^^^^^^
        |
        = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
        = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
      --> src/buffer.rs:59:16
       |
    59 |     #[cfg_attr(doc_cfg, doc(cfg(feature = "proc-macro")))]
       |                ^^^^^^^
       |
       = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
       = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
      --> src/data.rs:11:16
       |
    11 |     #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
       |                ^^^^^^^
       |
       = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
       = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
      --> src/data.rs:34:16
       |
    34 |     #[cfg_attr(doc_cfg, doc(cfg(any(feature = "full", feature = "derive"))))]
       |                ^^^^^^^
       |
       = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(doc_cfg)");` to the top of the `build.rs`
       = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration

    warning: unexpected `cfg` condition name: `doc_cfg`
       --> src/macros.rs:140:20
        |
    140 |           #[cfg_attr(doc_cfg, doc(cfg(feature = "printing")))]
        |                      ^^^^^^^
        |
       ::: src/data.rs:26:1
        |
    26  | / ast_enum_of_structs! {
    27  | |     /// Data stored within an enum variant or struct.
    28  | |     ///
    29  | |     /// # Synta…

build.rs

@@ -14,6 +14,12 @@ fn main() {
     // Note: add "/build.rs" to package.include in Cargo.toml if adding any
     // conditional compilation within the library.
 
+    println!("cargo:rustc-cfg=check_cfg");
+    println!("cargo:rustc-check-cfg=cfg(check_cfg)");
+    println!("cargo:rustc-check-cfg=cfg(doc_cfg)");
+    println!("cargo:rustc-check-cfg=cfg(syn_disable_nightly_tests)");
+    println!("cargo:rustc-check-cfg=cfg(syn_only)");
+
     if !unstable() {
         println!("cargo:rustc-cfg=syn_disable_nightly_tests");
     }

src/lib.rs

@@ -253,6 +253,7 @@
 #![cfg_attr(doc_cfg, feature(doc_cfg))]
 #![deny(unsafe_op_in_unsafe_fn)]
 #![allow(non_camel_case_types)]
+#![cfg_attr(not(check_cfg), allow(unexpected_cfgs))]
 #![allow(
     clippy::bool_to_int_with_if,
     clippy::cast_lossless,