Does anyone know what this is:
Delphi XE6 [dcc64 Fatal Error] .pas(): F2084 Internal Error: AV08F046D5-R00000000-0
I get it if I try
That is an internal compiler error. This is a compiler bug. The reported code means something to Embarcadero, and can be used to search to check if others have the same issue. Typically such errors are caused by very specific combinations of code and compiler options. It is not likely that anyone will be able to diagnose the cause of the error without such information.
If you can't find any other report of this issue, submit a QC report. The report needs to include minimal steps to reproduce. That means a short but complete program.