SourcePosition
Represents a position in a source file. Positions correspond to spaces between characters rather than characters themselves.
In a file with n characters, there are n + 1 positions: one before the first character, one after the last character, and n - 1 between each consecutive character.
Parameters
offset
Number of Chars (unicode code units, not code points) before this position, counting from the beginning of the file. Starts at 0.