Remove misleading code example from The Guide

[aochagavia]

The removed code caused confusion because it is not clear that the type of y is actually ()

[aochagavia]

cc @steveklabnik

I think the reader will not even notice we have skipped a piece of text.

[lilyball]

Eh, I think it's a useful thing to point out. It's contrasting variable assignment with a let item. Perhaps you should instead add a sentence to the end pointing out that the value of an assignment is ().

[aochagavia]

I think that is a valid alternative. However, at this point in the guide the () type has not been introduced, so it would require to rearrange the section.

EDIT: even if you do this, x = y = 5i is completely useless in real code. Why should we bother people with it?

[lilyball]

@aochagavia I think the point is to contrast a let statement with basically every other type of statement. Assignment is a statement in most languages, but in Rust it's actually an expression. It's not a particularly useful one, but it can in fact be used in a position where an expression is expected.

[steveklabnik]

I am super torn. @kballard nails it: it's to contrast that let is different than in other languages. However, I also agree with you, @aochagavia, that it's not useful.

So: can we accomplish this goal through some other example? Is there a time when let as expression has a valid use? If not, then I support removing it. If so, I'd support changing the example to that one.

[lilyball]

How about something like this:

Note that assigning to an already-bound variable is still an expression, although the value of the expression is not particularly useful. Unlike C, where an assignment evaluates to the RHS, in Rust the value of an assignment is the unit type () (which we'll talk about later).

No code example necessary. This explanation is largely just to avoid confusion in readers who read the info on let and decide to actually experiment with mere assignment.

[aochagavia]

I like it! Do you have any improvements on that @steveklabnik?

EDIT: maybe we can replace "RHS" for something more accessible for beginners.

[steveklabnik]

Yes, with the expansion of "right hand side," I think that's fine.

[aochagavia]

I have committed a slightly modified version. Please tell me if you think something needs to be changed.

[lilyball]

Actually I think "assigned value" instead of "right hand side" may be simpler.

[aochagavia]

I think you are right, check out the new version.

[steveklabnik]

Nice.