Correct, that's the whole point of using a range - it can come
from anything.
For example, let's suppose we want to do D syntax highlighting
in our IDE. It is highly unlikely that the text editor's data
structure is a simple string. It's likely to be an array of
lines, or something like that. It's simple to provide a range
interface to that, where it presents the data structure as a
sequence of chars.
Would this be an argument for putting the computation of source
locations (i.e. line + offset or similar) into the range / into
an template argument / policy, so that it's done in the most
effective way for the client?
Kate for example has a "range"-type that marks a span in the text
buffer. This way the lexer can return token with the correct
"textrange" attached and you don't need to recompute the text
ranges from line/col numbers.
