E100: Turf doesn't know that escape sequence

Inside a string or a character, a backslash \ starts an “escape sequence”: a short code for something you can’t easily type, like a line break. Turf knows exactly these:

\n   a new line          \t   a tab\r   carriage return     \0   the null character\\   a backslash         \"   a double quote\'   a single quote      \a \b \f \v   the rarer control characters

Anything else after a backslash is an error, because Turf would otherwise have to guess what you meant:

mut path: string = "C:\temp\q";     // \q is not an escape sequence

If you wanted a real backslash character, write it twice:

mut path: string = "C:\\temp\\q";

Most often this error is a Windows-style path or a regular expression with single backslashes in it. Double each backslash and it goes away.

Run turf --explain E100 in a terminal to read this again.