title: What's the solution for "error: Couldn't IRGen expression, no additional error" on Xcode 10.1?
body: <p>We have a large project with a lot of dependencies brought in through Carthage. Whenever we try to look at a variable in the lldb debugger (<code>p variablename</code>), it gives us an error: <code>error: Couldn't IRGen expression, no additional error</code></p>
  
  <p>None of the workarounds are very good. We can run carthage with <code>--no-use-binaries</code> to get around it, but it makes builds take a prohibitively long time. We can use <code>fr v</code> on some variables, but not all. People have fixed this in previous versions of Xcode by changing permissions on some Swift directories, but I can't find the corresponding directories in Xcode 10.1. And I saw someone say that changing the build system back and forth helped him, but that hasn't worked for us.</p>
  
  <p>So I'm starting this search for a solution on Xcode 10.1 specifically. Has anyone else found out what's causing this error, and/or a good solution to it?</p>