Consider defaulting a var/let declaration to auto type

[giucam]

In order to make a var/let declaration with type inference one needs to specify the type as auto, as in:

var foo: auto = 3;

It seems to me it would be more natural if you could just do

var foo = 3;

I think the auto there does not really do anything useful, while just being one more thing to type.

[sanxiyn]

FYI, it was considered, see proposal p0851, especially "Alternatives considered" > "Elide the type instead of using auto".

[GiorgosAlexakis]

It looks like the proposal was accepted??

[giucam]

The proposal lists these as disadvantages of eliding the type:

• Type inference becomes the lack of a type, rather than the presence of something different.
• C++'s syntax legacy may have needed auto in order to provide type inference, where Carbon does not.

I don't see why they would be disadvantages, the second one even seems an advantage to me, unless i misunderstand it.

• Removes syntactic distinction between binding of a new name and reference to an existing name, particularly for pattern matching. Reintroducing this distinction would likely require additional syntax, such as Swift's nested let.

I can see though that this one is a valid concern, although having to specify var in a value binding pattern doesn't seem like a problem to me.

[jonmeow]

I don't see why they would be disadvantages, the second one even seems an advantage to me, unless i misunderstand it.

Oops, that looks like my mistake.

But I think the leads were really focused on type inference becoming the lack of a name, and generally wanting to encourage writing types explicitly. I don't know how much that'll shift as more feedback arrives.