solc-v0.6.0: TypeError: Operator - not compatible with types tuple() and int_const 1

Question

I am having this error on solc version 0.6.0.

Basically I am returning length of the list and subtract 1 from it, where that value will be assigned to an uint variable.

In general this command used to return the length of the list after the push:

uint length = list.push(Struct({val: value}))

---

TypeError: Operator - not compatible with types tuple() and int_const 1
uint32 value = uint32(list.push(Interval({endpoint: startTime})) - 1);

I was not getting this error or solc-v0.5.*. I feel like tuples does not return their length any more.

[Q] How could I fix this error?

Answer 1

Yes, list.push will not return the length of it anymore.

From https://solidity.readthedocs.io/en/v0.6.0/060-breaking-changes.html#how-to-update-your-code:

Change uint length = array.push(value) to array.push(value);. The new length can be accessed via array.length.

So, now you must do it "manually":

pragma solidity 0.6.0;

contract Test {
    struct Interval {
        uint endpoint;
    }

    Interval[] public list;

    function addItemAndGetLengthMinusOne() public returns(uint) {
        list.push(Interval({endpoint: now}));
        uint value = list.length - 1;

        return value;
    }
}