RE: `read--expression' and `read-minibuffer'

[Drew Adams]

> >>> Because it is tailored for that use case.  The kind of completion
> >>> it provides for instance assumes the S-exp is an Elisp expression.
> >> Of course it is an Elisp expression.  It does not follow that
> >> the Elisp expression that has been read will then be _evaluated_.
> > In this thread, Stefan is defining an "Elisp expression" to be precisely
> > an S-exp that is intended for `eval'.
> 
> Not necessarily directly for `eval', but yes an Elisp expression as
> opposed to random S-exp data.  E.g. when reading an alist, you shouldn't
> use read--expression (whereas, when reading an expression that will
> evaluate to an alist, read--expression is probably the right thing to
> use).
> 
> > So a variant of `read--expression' could be written that does a subset
> > of that completion appropriate to the more general context of entering
> > an S-exp.
> 
> For any random S-exp data, we already have `read-minibuffer', so I don't
> see any point in changing read--expression to cover that case.

Completion of parts of the data.  Just as in the function-application
sexp case.  There just is assumption that the first symbol after `('
should complete against only function symbols.