warning: unexpected `cfg` condition value: (none)
  --> $DIR/concat-values.rs:6:7
   |
LL | #[cfg(my_cfg)]
   |       ^^^^^^
   |
   = note: expected values for `my_cfg` are: `bar`, `foo`
   = help: to expect this configuration use `--check-cfg=cfg(my_cfg)`
   = note: see <https://doc.rust-lang.org/nightly/unstable-book/compiler-flags/check-cfg.html> for more information about checking conditional configuration
   = note: `#[warn(unexpected_cfgs)]` on by default

warning: unexpected `cfg` condition value: `unk`
  --> $DIR/concat-values.rs:10:7
   |
LL | #[cfg(my_cfg = "unk")]
   |       ^^^^^^^^^^^^^^
   |
   = note: expected values for `my_cfg` are: `bar`, `foo`
   = help: to expect this configuration use `--check-cfg=cfg(my_cfg, values("unk"))`
   = note: see <https://doc.rust-lang.org/nightly/unstable-book/compiler-flags/check-cfg.html> for more information about checking conditional configuration

warning: 2 warnings emitted