Unfortunate but probably shouldn't be running gofmt on files with //line comments anyway. Can wait for Go 1.7.

@griesemer, do you still want to do this for Go 1.9? It missed the past 4 releases and still repros.

@bradfitz I will need to see who complicated the fix is, first. I won't get to this before June 1.

I don't think we should do anything here: Fixing this would mean that once we see a //line directive we're not allowed to move anything that follows later to a different line. At the very least, that is the assumption we have to make until we see the next //line comment. But that interferes directly with gofmt's main purpose which is to organize white space for uniform formatting. One "solution" would be to not move any lines that follow a //line comment. But it's pretty tricky to get this correct under all circumstances. I'm not convinced the amount of complexity is worth the few cases where it might matter. I don't want to go down that route.

The situation is additionally complicated by the fact that the go/printer has a mode that emits //line comments.

I've recently fixed #5945 which makes sure that the above-mentioned mode only prints //line directives immediately before non-whitespace. Code that is printed that way will pass through gofmt undisturbed.

In other words, don't use //line directives in front of empty lines - use them where it matters. Or don't gofmt such files.

Closing as unfortunate.