Improve heuristics whether `format_args` string is a source literal

Previously, it only checked whether there was _a_ literal at the span of
the first argument, not whether the literal actually matched up. This
caused issues when a proc macro was generating a different literal with
the same span.

This requires an annoying special case for literals ending in `\n`
because otherwise `println` wouldn't give detailed diagnostics anymore
which would be bad.

0 files changed, 0 insertions, 0 deletions