warning: unexpected `cfg` condition name: `foo`
  --> $DIR/doc-cfg-check-cfg.rs:12:12
   |
LL | #![doc(cfg(foo))]
   |            ^^^
   |
   = help: to expect this configuration use `--check-cfg=cfg(foo)`
   = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
   = note: `#[warn(unexpected_cfgs)]` on by default

warning: unexpected `cfg` condition name: `foo`
  --> $DIR/doc-cfg-check-cfg.rs:19:11
   |
LL | #[doc(cfg(foo))]
   |           ^^^
   |
   = help: to expect this configuration use `--check-cfg=cfg(foo)`
   = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration

warning: unexpected `cfg` condition name: `foo`
  --> $DIR/doc-cfg-check-cfg.rs:15:11
   |
LL | #[doc(cfg(foo))]
   |           ^^^
   |
   = help: to expect this configuration use `--check-cfg=cfg(foo)`
   = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration

warning: 3 warnings emitted