let mut, var imm or let var, var let

[igotfr]

For instance:

let (a, mut b, c) = (d, e, f);

var (a, imm b, c) = (d, e, f);

or

let (a, var b, c) = (d, e, f);

var (a, let b, c) = (d, e, f);

[lexi-nadia]

This could be written using current syntax as:

let a = d;
var b = e;
let d = f;

Personally, i find this easier to read than the proposal; i don't have to correlate names on the left with values on the right.

Do you have a motivating example to show how the proposed syntax would help?

[igotfr]

This could be written using current syntax as:

let a = d;
var b = e;
let d = f;

Personally, i find this easier to read than the proposal; i don't have to correlate names on the left with values on the right.

Do you have a motivating example to show how the proposed syntax would help?

I can want destructuring a tuple, array or struct which each member has different mutabilities

[jonmeow]

At present, I think that's

let (a: auto, var b: auto, c: auto) = (d, e, f);

To try to summarize, this is because var is supposed to guarantee storage, whereas let isn't. So a var inside let is essentially saying "even though the tuple doesn't need storage, this part does". By contrast, it's hard to say "even though this tuple needs storage, this part doesn't".

Example: https://github.com/carbon-language/carbon-lang/blob/trunk/explorer/testdata/let/nested_tuple_pattern.carbon