fn validate_feature_definitions(
cargo_features: &Features,
features: Option<&BTreeMap<FeatureName, FeatureDefinition>>,
warnings: &mut Vec<String>,
) -> CargoResult<()>fn validate_feature_definitions(
cargo_features: &Features,
features: Option<&BTreeMap<FeatureName, FeatureDefinition>>,
warnings: &mut Vec<String>,
) -> CargoResult<()>