ast gets the wrong column information for interpolated code in multiline f-strings

[martindemello]

Bug report

When parsing multiline f-strings, e.g.

a = f"""
     {test}
    """

the ast has the wrong column information for test. Here's the diff between 3.9.12 (lhs, gets it wrong) and 3.9.1 (gets it right).

     FormattedValue(                                                 FormattedValue(
      value=Name(                                                     value=Name(
       id='test',                                                      id='test',
       ctx=Load(),                                                     ctx=Load(),    
       lineno=2,                                                       lineno=2, 
       col_offset=11,                                         |        col_offset=7,                                  
       end_lineno=2,                                                   end_lineno=2,                                  
       end_col_offset=15),                                    |        end_col_offset=11),         

Your environment

Tested on a variety of python versions (on linux); 3.9.1 gets it right, it's wrong in 3.9.2 and has the same wrong value all the way to 3.9.12. The offset seems related to the start column of the opening triple quotes. I went through previous f-string parsing bugs but this does not look like a duplicate of any of them.

[ericvsmith]

@pablogsal : thoughts?

[pablogsal]

Yeah, this looks like a bug. I will take a look after EuroPython

[martindemello]

seems to have been caused by bfc413c

[pablogsal]

Unfortunately 3.9 is in security fixes only so we cannot backport this fix :(