Xcode 8 debugger doesn't print objects and showing expression produced error

Question

I have upgraded Xcode 8 but when I'm debugging, every object showing following error :

expression produced error: error: Couldn't materialize: couldn't get the value of __once: extracting data from value failed
error: errored out in DoExecute, couldn't PrepareToExecuteJITExpression

This seems system level error, so I've already tried all possible solutions but still doest work.

Answer 1

I don't know of any bug that would cause this to happen for all types. Except, if this is a Swift project, make sure that you have cleaned and rebuilt all the swift code you depend on from source. At present, Swift really needs the whole world to be built consistently for debugging to work. If that doesn't help, then we will need more details to figure out what is going wrong.

Might be worthwhile to file a bug with http://bugreporter.apple.com since that makes gathering the data needed to solve the problem easier.