Improved support for destructuring tuples with partially declared outputs

Language Design
1

Hey,

Wondering about thoughts on the following

    function _tuple() internal pure returns (uint, uint) {
        return (1, 1);
    }
    
    function outer() internal pure {
        // valid
        (uint a, uint b) = _tuple();
        
        // valid
        uint c; uint d;
        (c, d) = _tuple();

        // invalid
        uint e;
        (e, uint f) = tuple();

    }

Looks to me like tuples require destructing all elements either into predefined variables, or require inline declarations for all elements.

I understand there might be practical reasons for this, and would be interested to hear them. I was expecting to be able to “mix and match” between previously declared variables and newly declared variables.

Would be interested to hear if this would be a useful change or if there are major technical hurdles behind implementing something like this?

2

I don’t see any technical problems with this. Other than maybe adding more possible corner cases in the compiler where things could go wrong. So it’s mostly a question of how useful would that be in practice.

3

I ran into it today, I wouldn’t say it’s coming up all the time but from an “expected behaviour” standpoint it took me a minute to work out what my syntax error is. Would be a nice fix depending on the time/effort required

4

You could submit a feature request, though I’d say that it would be very low priority for us right now so might be better to first see if more people would find that useful.

5

Definitely useful for me as a nice to have. Sometimes I have to declare 2 or 3 extra variables right before destructuring the tuple just so I can reuse previous variables and the code is a bit less readable. @cameel where should we do the feature request?

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