Lazarus 1.8.0 with FPC 3.0.4, running on Windows 10 64-bit.
In a few cases throughout my project, I have event handler procedures that have arguments that don't get used in the procedures. To keep the compiler output tidy, I usually surround these with {$warn 5024 off} (and on again afterwards). I don't want to just leave it off for the whole project, but rather, specifically disable it during code that I know has unused parameters and isn't meant to be using them.
Adding it on some methods, however, gives a "Error: Message recordind not yet supported" compiler error. I'm not really noticing any pattern as such of what will or won't cause this. The error is never on the block inside the {$warn 5024 off} section, but on other methods later in the file - usually if the error occurs, it occurs on almost every method in the rest of the file. It doesn't seem to ever affect other units. In some cases, using {$hints off} (and on) instead will compile without problem.
The same code, except without the warning toggles, compiles without issue.
Can confirm this issue also happens on Mac OS X, same Lazarus and FPC version, 32-bit compiler.