PrintError is a utility function that prints a list of errors to w, one error per line, if the err parameter is an ErrorList.

do not report an error for illegal chars.

automatically insert semicolons.

sort error list and leave only the first error per line.

leave error list unchanged.

return comments as COMMENT tokens.

sort error list by file, line, and column number.

Within ErrorVector, an error is represented by an Error node.

ErrorVector implements the ErrorHandler interface.

A Scanner holds the scanner's internal state while processing a given text.

An implementation of an ErrorHandler may be provided to the Scanner.

An ErrorList is a (possibly sorted) list of Errors.