Character offset on a line in a document (zero-based).
The meaning of this offset is determined by the negotiated
PositionEncodingKind.
If the character value is greater than the line length it defaults back to the line length.
Line position in a document (zero-based).
If a line number is greater than the number of lines in a document, it defaults back to the number of lines in the document. If a line number is negative, it defaults to 0.
A document URI and a position in that document.