The constructor for Gobstones lexer InvalidEscapeCharWarningIn warning.
A string indicating the particular string value where the escape occurs.
Optional
span: SpanThe span in the source where the token where error was detected started. It may be undefined, in which case an Unknown span is used (with both start and end as UnknownPosition).
A Lexer warning signaling that an escape character inside a string is invalid (not in the list of expected escaped characters).