Should work? let a; let b; (a, b) = (1, 2);

[jeaye]

This seems like it should be allowed, but it errors out with:

<anon>:5:24: 5:25 error: use of possibly uninitialized variable: `a`
<anon>:5          let a; let b; (a, b) = (1, 2); b
                                 ^
<anon>:5:27: 5:28 error: use of possibly uninitialized variable: `b`
<anon>:5          let a; let b; (a, b) = (1, 2); b
                                    ^
error: aborting due to 2 previous errors
application terminated with error code 101

[thestinger]

It's not allowed, only let, match and parameters use patterns.

#7508

[thestinger]

Allowing binding to an lvalue in a pattern seems like RFC material but I don't know how feasible it is. It's not as simple as just the usage here.

[glaebhoerl]

There was discussion of this idea on reddit: http://www.reddit.com/r/rust/comments/1hsqf5/proposal_for_an_additional_use_case_of_the_in/, with the objection being that it would prevent the grammar from being LL(finite number).