[clang-tidy] TransformerClangTidyCheck: change choice of location for diagnostic message.
This patch changes the location specified to the
ClangTidyCheck::diag(). Currently, the beginning of the matched range is
used. This patch uses the beginning of the first fix's range. This change both
simplifies the code and (hopefully) gives a more intuitive result: the reported
location aligns with the fix(es) provided, rather than the (arbitrary) range of
the rule's match.
N.B. this patch will break the line offset numbers in lit tests if the first fix
is not at the beginning of the match.
Subscribers: xazax.hun, cfe-commits
Differential Revision: https://reviews.llvm.org/D66676