Bring conditionals back since the HIR change.

[philberty]

Example:

fn main() {
    let mut x = 5;

    if x == 5 {
        x = 1;
    } else if x == 3 {
        x = 2;
    } else {
        x = 3;
    }
}

GIMPLE

void main ()
{
  i32 mut x;

  mut x = 5;
  if (mut x == 5) goto <D.188>; else goto <D.189>;
  <D.188>:
  {
    mut x = 1;
  }
  goto <D.190>;
  <D.189>:
  {
    if (mut x == 3) goto <D.191>; else goto <D.192>;
    <D.191>:
    {
      mut x = 2;
    }
    goto <D.193>;
    <D.192>:
    {
      mut x = 3;
    }
    <D.193>:
  }
  <D.190>:
}

[SimplyTheOther]

PR seems great.

[SimplyTheOther]

This relates to something I had thought about doing, but not in enough detail to open an enhancement issue. gcc supports something called "rich locations" in which three actual locations are encoded - a "start" location, a "caret" location, and an "end" location - basically like a location range with a specified value highlighted.

I couldn't find the page that I thought I originally read this in, but here's a quote from here:

As of GCC 6, ordinary locations changed from supporting just a point in the user’s source code to supporting three points: the caret location, plus a start and a finish:

      a = foo && bar;
          ~~~~^~~~~~
          |   |    |
          |   |    finish
          |   caret
          start

Instead of accessing start_location and end_location separately, these could be integrated into a single location value. There's also the technicality that the current definition of get_closing_locus() technically gets the beginning location of the last statement rather than the end location of the block (i.e. the right curly bracket), assuming that this would be the preferred behaviour.

The lexer would have to be modified to reflect this rich location system, and the parser and AST probably would have to be too (i.e. make a new location from the "start" location from one token and the "end" location of a different one). Also, the backend-independent Location abstraction would have to be modified to support this.

[philberty]

Good point, this closing locus is mostly a placeholder it just returns get_locus. I think there needs to be an issue about the diagnostics in general. gccgo added extra specifiers to the format string which might give some inspiration. Though the Fortran front-end is usually deemed to be the gold standard these days.