Re: next-error-last-buffer

[Richard Stallman]

    > So the only change needed is to modify the rule order like you proposed,
    > which could look as below:
    > 
    > 1. If one window on the selected frame displays such buffer, return it.
    > 2. If next-error-last-buffer is set to a live buffer, use that.
    > 3. If the current buffer is a next-error capable buffer, return it.
    > ...

That might solve the problem, but what you have written is very
different:

    +;; 1. If next-error-last-buffer is set to a live buffer, use that.
    +;; 2. If the current buffer is a next-error capable buffer, return it.
    +;; 3. If one window on the selected frame displays such buffer, return it.
     ;; 4. Otherwise, look for a next-error capable buffer in a buffer list.
     ;; 5. Signal an error if there are none.

This change has the unpleasant side effect of eliminating any
convenient way to control which buffer you want to take errors from.
next-error-last-buffer takes precedence over everything else,
so there is no way to deliberately override it.

Using the current buffer is wrong only in one special case: where that
buffer was found as the source locus for an error.  In all other
cases, it is right to use the current buffer rather than
next-error-last-buffer.