(U)Int `arbitrary` implementation provides limited values with `.proliferate(withSize:)`

[nesevis]

Version

077c096c3ddfc38db223ac8e525ad16ffb987138

Environment

• macOS 11.6
• Xcode 13.1RC
• 2019 Intel 16" MBP

Description

When combined with proliferate(withSize:), (U)Int[8|16|32|64].arbitrary will only generate values from -30 to 30 if signed, and 0 to 30 if unsigned.

Steps To Reproduce

Set(UInt.arbitrary.proliferate(withSize: 2000).generate).sorted()

Expected Result

Random values in a wider range

Actual Result

Very limited range of random values

Additional information

None

[Qata]

This is intentional behaviour.

From Gen.swift:

/// Generates a value.
///
/// - Attention: This property exists as a convenience mostly to test
///   generators.  In practice, you should never use this property because
///   it hinders the replay functionality and the robustness of tests in
///   general.
public var generate : A {
    let r = newStdGen()
    return unGen(r, 30)
}