A dynamic array declared in a function cannot be substituted away.

[pirapira]

The violated property

In general,

<type> v = a;
<code contaning v>

should be equivalent to

<code containing a>

if a does not have side-effects.

The violation

However, this property does not hold in Solidity because

contract C {
    uint[] a;
    uint[] b;
    function f() {
        uint[] ref = a;
        ref = b;
    }
}

behaves quite differently from

contract C {
    uint[] a;
    uint[] b;
    function f() {
        a = b;
    }
}

The latter performs elementwise copy while the former does not.

[chriseth]

Solidity is not the only language that does not have this property. Python for example, a language that is usually considered to be very intuitive or at least easy to learn behaves like that:

>>> a = [1,2,3]
>>> b = [4,5]
>>> ref = a
>>> ref = b
>>> a
[1, 2, 3]
>>> b
[4, 5]

>>> a = [1,2,3]
>>> b = [4,5]
>>> a = b
>>> a
[4, 5]
>>> b
[4, 5]

[chriseth]

In general, I think that #2435 should make this distinction clear to the programmer.

[pirapira]

Yes, I have the same complaint against Python.

[pirapira]

After #2435, it should be straightforward to fix this issue, whether element-wise copying into a reference is allowed or not.

[github-actions]

Hi everyone! This issue has been closed due to inactivity.
If you think this issue is still relevant in the latest Solidity version and you have something to contribute, feel free to reopen.
However, unless the issue is a concrete proposal that can be implemented, we recommend starting a language discussion on the forum instead.