This removes a (very) hot branch in the lexer where we need to special
case when a token is the first token and can't look at its previous
token. It also seems like a generally nice change to the structure of
both the token buffer and parse tree as there are now bracketing
elements for both ends and we should be able to avoid similar branching
in the future.
Mostly mechanical updates to the lexer and parser code to handle this,
but also needed to special case the location information in the
autoupdate code. And then the usual large body of auto-updated tests.
No benchmark data for this change alone as in isolation and in the
current lexer structure it doesn't make a big difference. But this
branch was particularly difficult to handle when trying to update the
whitespace skipping code to be faster, and so I think it is worth
systematically avoiding the special case here.
Lex now prints its yaml as:
```
- filename: name
tokens: [ ... ]
```
New support in file_test allows the `filename` marker at the top to
define the default file number for later lines, meaning multi-file
output from lexing is now associated with the appropriate file. Similar
support will probably also apply to lowering, semir, and other places
that print a filename once for the full dump.
This hammers a bit at how line number replacements work in file_test,
allowing stacking them so that lex errors and stdout can both be
line-associated properly. I've tried to make the autoupdate more
frequently work in one pass, now also taking into account the file index
when doing line replacements.
There are still some issues with EndOfFile that it may be good to
discuss: because CHECK lines are appended to the end of the file now,
and the EndOfFile token points at the last line including comments, new
lex tests now take two runs to autoupdate (because without CHECK lines,
the EndOfFile points at a content line, which content is then inserted
after). Note that removing CHECK lines from the test is not a solution:
autoupdate also started inserting blank lines, which breaks this for a
similar reason. One solution here might be to not have EndOfFile
associate with a line or column, which has been a bit of an issue
regardless.
Also fixes a small issue with toolchain's autoupdate script.
Continuing with #3070. Just a dir and file rename (only prefix change is
lexer_file_test). Everything in the lex dir should be marked as a move.
Note, I think this closes#3070. There may still be further cleanup
later, but the organizational changes suggested there are being
completed.
---------
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Jon Ross-Perkins
Chandler Carruth