The error when change the c# code.

It is very easy to get "Copying assembly from directory Temp to Library/ScriptAssemblies failed" error when change the c# code.
I have to relaunch the editor to fix this. I am using 2018.2 beta with the new package manager and dotnet 4.x~

 

That's a known issue with the Incremental Compiler. It's being worked on, but there's no fix right now.

Instead of closing Unity, you can try and reimport a cs or asmdef file, to trigger another recompilation. It should work (that's what I do).

 

I am not using the Incremental Compiler, at least I do not install it in package manager.
I am using the Unity2018.2b8.

 

There are packages that depend on it and will install it automatically.
Do you have a "Compiler" section in your editor preferences (Edit -> Preferences)? If it's there, the compiler was installed by something else (maybe the entities packages).

If it's not there, this might be something else. Maybe submit a bug report and paste the # back here so the devs can take a look.

 

No, there is no Compiler page in perferences.

 

Oh, that's new!

Could you submit a bug report with a repro project?