swift-format Incorrectly duplicates comments to subsequent lines

[gvozdvmozgu]

When formatting Swift code using swift-format, comments from one line are improperly duplicated to the following lines.

Steps to Reproduce:

1. Create a Swift file (test.swift) with the following content:

   1 // test
   +1

2. Run the following command to format the code:

   swift run swift-format test.swift

3. Check the contents of test.swift after formatting:

   1  // test
   +1  // test

[ahoppen]

Synced to Apple’s issue tracker as rdar://137698840