P.S.: to get get the specifity of linenumbers without the brittleness,
we could have a pragma for the extra dump line tag instead. Either till
the next such pragme / EOF, or (if before next such pragma), till the
end of function.
Disadvantages: Not actually more specific when the source describes a
template, or gets cloned. Unless we add the mangled filename too,
either unconditionally, per option, or per format (complex, bugprone).
The tag would have to be associated with or included in the source
location. That might get complex and be a source of bugs in itself.
