Xcode 10.0 Beta 4 was released on 17 Jul 2018 and requires macOS 10.13.4+.
It can be downloaded from https://download.developer.apple.com/Developer_Tools/Xcode_10_beta_4/Xcode_10_beta_4.xip.
Release notes are located at https://download.developer.apple.com/Developer_Tools/Xcode_10_beta_4/Release_Notes_for_Xcode_10_beta_4.pdf.
The SDKs it contains are:
- iOS 12.0 (Build 16A5327d)
- macOS 10.14 (Build 18A336d)
- tvOS 12.0 (Build 16J5322d)
- watchOS 5.0 (Build 16R5322d)
The compilers it contains are:
- clang 10.0.0 (Build 1000.10.40.1)
- swift 4.2 (Build 1000.0.29.2)