Xcode 10.0 Beta 1 was released on 4 Jun 2018 and requires macOS 10.13.4+.
It can be downloaded from https://download.developer.apple.com/Developer_Tools/Xcode_10_Beta/Xcode_10_Beta.xip.
Release notes are located at https://download.developer.apple.com/Documentation/Beta_Release_Notes_Jun_4_2018/Xcode_10_Beta_Release_Notes.pdf.
The SDKs it contains are:
- iOS 12.0 (Build 16A5288q)
- macOS 10.14 (Build 18A293s)
- tvOS 12.0 (Build 16J5283n)
- watchOS 5.0 (Build 16R5283q)
The compilers it contains are:
- clang 10.0.0 (Build 1000.10.25.5)
- swift 4.2 (Build 1000.0.16.7)