How-to

Some features are available directly as Xcode Build Settings while others can be passed as build command line arguments or settings in a Swift Package Manager Package.swift file.

Programatically, it's possible to determine if a feature is available using the #if directive:

#if hasFeature(StrictConcurrency)
#endif

See Proposa SE-0362 for more details.

Upcoming

A compiler flag is available to enable specific features -enable-upcoming-feature FeatureName. In SPM, features can be enabled in Package.swift using the enableUpcomingFeature setting:

.target(
    name: "TargetName",
    swiftSettings: [
        .enableUpcomingFeature("FeatureName")
        ])

Experimental

A compiler flag is available to enable specific features -enable-experimental-feature FeatureName. In SPM, features can be enabled in Package.swift using the enableExperimentalFeature setting:

.target(
    name: "TargetName",
    swiftSettings: [
        .enableExperimentalFeature("FeatureName")
        ])