Compiling string in memory not working because of an assert

Hi all,

I’m trying to build a string from memory using FrontendInputFile. As it cqn take a memory buffer or a file, it should work.
Unfortunately, in FrontendAction, there is a StringRef InputFile = Input.getFile() which logically fails.

Is this not supported? If so, why doesn’t it fail with a more explanatory message? Why would there still be the API if frontendAction doesn’t work with memory buffer? And if it’s supposed to work, what happened?