Empty else clause with only a comment seems to confuse syntaxsuggest

[mame]

class Foo
  def foo
    if cond?
      foo
    else
      # comment
    end
  end

  # ...

  def bar
    if @recv
    end_is_missing_here
  end
end

Expected: Around end_is_missing_here is displayed

Actual:

error.rb: --> error.rb
Unmatched keyword, missing `end' ?
   1  class Foo
   2    def foo
>  3      if cond?
>  5      else
   8    end
  16  end

This might be a variant of #177.

[schneems]

Thanks for the report. I saw it come in. I've not had a chance to investigate yet. I'm guessing the logic from the fix last time either introduced the issue, or we need to introduce some new logic https://github.com/ruby/syntax_suggest/blob/main/lib/syntax_suggest/around_block_scan.rb#L259.

[schneems]

The comment or empty line has a problem because it's not evaluated and "removed" the same way a branch with code will be. It fails like this:

    Block lines: 4..4 (add) 

   1  class Foo
   2    def foo
   3      if cond?
>  4        foo
   5      else
   6
   7      end
   8    end
   9
  10
  11
  12    def bar
  13      if @recv
  14      end_is_missing_here
  15    end
  16  end

    Block lines: 3..5 (expand) 

   1  class Foo
   2    def foo
>  3      if cond?
>  5      else
   6
   7      end
   8    end
   9
  10
  11
  12    def bar
  13      if @recv
  14      end_is_missing_here
  15    end
  16  end

With those lines, then the kw/end pairs balance like this:

    Block lines: 3..5 (expand) 

   1  class Foo
   2    def foo
   6
   7    end
   8  end
   9
  10
  11
  12    def bar
  13      if @recv
  14      end_is_missing_here
  15      end
  16    end

If you replace that line with any literal that's not a comment it will work because each side of the "else" is evaluated and removed and then when "indent expand" is called, it pulls in both the else and it's end since at that point it seems to the program they belong together:

    Block lines: 4..4 (add) 

   1  class Foo
   2    def foo
   3      if cond?
>  4        foo
   5      else
   7      end
   8    end
   9
  10
  11
  12    def bar
  13      if @recv
  14      end_is_missing_here
  15    end
  16  end

    Block lines: 3..7 (expand) 

   1  class Foo
   2    def foo
>  3      if cond?
>  5      else
>  7      end
   8    end
   9
  10
  11
  12    def bar
  13      if @recv
  14      end_is_missing_here
  15    end
  16  end

The difference between #177 and this is that the problem is on the "indent" block expansion rather than the "neighbors" block expansion. I'm hoping we can apply similar logic to work around the issue.