bug#3400: bug in add-text-properties

[martin rudalics]

> The first line properly disappears, however, the first character in
> the now visible part of the buffer (the letter `a') makes problems: It
> incorrectly refers to the character at buffer position 1 (the digit
> `1').  In particular, `C-u C-x =' for letter `a' shows
>
> ---
>
>         character: 1 (49, #o61, #x31)
[...]
> There are text properties here:
>   intangible           t
>   invisible            t

`add-text-properties' describes the character after point and when you
call `describe-char' point is at the beginning of the buffer.  So IMHO
this is not a bug in `add-text-properties'.  It's arguable whether point
should be allowed to be there in your case, but then where to move point
when the entire buffer is invisible?

> A side effect is that `C-a' no longer moves to the beginning of the
> line.

A side effect of what?

martin