bpo-43950: support some multi-line expressions for PEP 657

[isidentical]

This is basically something that I noticed up while fixing test runs for another issue. It is really common to have multiline calls, and when they fail the display is kind of weird since we omit the annotations. E.g;

 $ ./python t.py
Traceback (most recent call last):
File "/home/isidentical/cpython/cpython/t.py", line 11, in <module>
frame_1()
^^^^^^^^^
File "/home/isidentical/cpython/cpython/t.py", line 5, in frame_1
frame_2( File "/home/isidentical/cpython/cpython/t.py", line 2, in frame_2
return a / 0 / b / c
~~^~~
ZeroDivisionError: division by zero

This patch basically adds support for annotating the rest of the line, if the instruction covers multiple lines (start_line != end_line).

https://bugs.python.org/issue43950

Automerge-Triggered-By: GH:isidentical

[pablogsal]

I recall they we had this version implemented but we did abandoned it because it looked weird in done scenarios. I am missing anything or is the fact that we are stopping in whitespace enough to account for the problems with the old approach?

[isidentical]

The old approach was highlighting the whole line if the end_offset is greater than 256 (-1) but where the instruction was only covering a single line. This is about when an expression covers multiple lines (e.g the call above). Since we now the start point, and we know for a fact that the instruction continue to next lines we can just highlight the line to the end without any false positives.

[pablogsal]

Can you add some extra tests with some specific cases like function calls spawning multiple lines as well as binops spawning multiple lines (for example)? I will like to cover this with more cases if possible,

[pablogsal]

LGTM modulo my comment regarding more tests

[miss-islington]

@isidentical: Status check is done, and it's a success ✅ .