My experience with this is the other way around, especially if you have crates tied to that feature.

The cfg! is a marco that compiles to true/false, so whatever is inside of the if guard needs to compile regardless.

E.g.:

Cargo.toml

    [features]
    default = []
    my_feature = ["deps:feature_dependency"]

    [dependencies]
    feature_dependency = "1.0.0"

    if cfg!(feature = "my_feature") {
        feature_dependency::something::Something::invoke();
    }