In cases "\\@" and "\@", the output will be "@"

@ is the expected output for "\@", as that's the correct escape sequence for a literal at sign.

This is likely an issue in the parser. With one backslash char, smart_string('\\@') properly results in @, and with two backslash chars, smart_string('\\\\@') properly results in \@, so the compiler function representing the smart string seems to work properly.