RE: Usability suggestion : completion for M-:

[Drew Adams]

> > Fine. Allow me to be the exception. We can do better.
> > M-: can be better still.
> 
> Agree, but in the meantime, binding TAB to tabulation character
> instead of symbol completion in the current one-line minibuffer is
> inconsistent with the behaviour of others minibuffer prompts.

On the contrary. TAB in the minibuffer either (1) self-inserts (when not
using completing-read or read-file-name) or (2) completes the entire
minibuffer input in such a way that you can hit RET to enter the completed
input. 

That's the case now for all minibuffer input. What you propose is
inconsistent with that. You are proposing something new: (3) complete only
part of the input, so that RET after TAB won't necessarily make sense.

That's OK, _if_ there are mitigating reasons - blind, systematic consistency
is not a goal in itself. But please recognize that the current TAB bindings
are consistent, and your proposal breaks that consistency. 

Why do that, especially if, as you admit, it is just a temporary hack: "in
the meantime"? In-the-meantime changes can become fixed by neglect, for no
special reason, rather than being just temporary exceptions to the rule. The
result of lots of such changes would be ad-hoc inconsistency throughout the
UI.

If the right thing to do is (as you apparently agree) to improve M-: so that
it is more like Lisp modes, with TAB assuming its indenting role (or perhaps
a hybrid indenting role), then we should not DTWT "in the meantime".