Almost everything is an accessor.
new($file,$line,$column,$text)
Create an object. It's not very exciting.
$file can be "undef" or an empty string, in which case it will not appear in messages.
as_string()
Returns a nicely-formatted string for printing out to stdout or some similar user thing.
file()
Returns the filename of the error, as set by the caller.
type()
Returns the type of the error. This will either be "TIDY_ERROR", or "TIDY_WARNING".
line()
Returns the line number of the error, or 0 if there isn't an applicable line number.
column()
Returns the column number, or 0 if there isn't an applicable column number.
text()
Returns the text of the message. This does not include a type string, like "Info: ".