Function cargo::core::features::nightly_features_allowed

pub fn nightly_features_allowed() -> bool

This is a little complicated. This should return false if:

• this is an artifact of the rustc distribution process for “stable” or for “beta”
• this is an #[test] that does not opt in with enable_nightly_features
• this is a integration test that uses ProcessBuilder that does not opt in with masquerade_as_nightly_cargo This should return true if:
• this is an artifact of the rustc distribution process for “nightly”
• this is being used in the rustc distribution process internally
• this is a cargo executable that was built from source
• this is an #[test] that called enable_nightly_features
• this is a integration test that uses ProcessBuilder that called masquerade_as_nightly_cargo