print=check-cfg

The tracking issue for this feature is: #125704.

This option of the --print flag print the list of expected cfgs.

This is related to the --check-cfg flag which allows specifying arbitrary expected names and values.

This print option works similarly to --print=cfg (modulo check-cfg specifics):

• check_cfg syntax: output of --print=check-cfg
• cfg(windows): windows
• cfg(feature, values("foo", "bar")): feature="foo" and feature="bar"
• cfg(feature, values(none(), "")): feature and feature=""
• cfg(feature, values(any())): feature=any()
• cfg(feature, values()): feature=
• cfg(any()): any()
• nothing: any()=any()

To be used like this:

rustc --print=check-cfg -Zunstable-options lib.rs