C# Interactive window: Help folks use #r directive with better error message

[AArnott]

Version Used: VS 2019 Update 9 preview

I failed to load an assembly the first time I tried:

#r @"D:\git\streamjsonrpc\bin\StreamJsonRpc.Tests\Debug\netcoreapp3.1\MessagePack.dll"
(1,4): error CS7010: Quoted file name expected

This puzzled me because I gave it a quoted file name. I eventually figured out that it didn't like the @ in the front. This was very unexpected because in general the code this window accepts is C#, and the error message did not help me discover my mistake. Can the error message here be improved?

[tmat]

This would require a change in the parser - changing the message for CS7010 for all directives that take strings.