On Thursday, 29 July 2021 at 20:44:35 UTC, Elronnd wrote:

Casting const away is undefined behaviour in D. And what is this "require"? Maybe show more code?

On Wednesday, 4 August 2021 at 08:08:35 UTC, Tejas wrote:

what's wanted here is an assign-once hash table, I imagine.

require is https://dlang.org/phobos/object.html#.require , and it'd be the assignment line of that code that would have to cast away const.

unittest {
    int[int] nums;
    nums.require(0, 0);
    nums[0]++;
    assert(nums == [0: 1]);
}

unittest {
    const(int)[int] nums;
    assert(__traits(compiles, nums.require(0, 0)));
    assert(!__traits(compiles, nums[0]++));
}

On Wednesday, 4 August 2021 at 09:43:57 UTC, jfondren wrote:

unittest {
    int[int] nums;
    nums.require(0, 0);
    nums[0]++;
    assert(nums == [0: 1]);
}

unittest {
    const(int)[int] nums;
    assert(__traits(compiles, nums.require(0, 0)));
    assert(!__traits(compiles, nums[0]++));
}

Well, OP will have to create non-const AA first and then cast it to const, it seems.

import std;
void main()
{
    int[int] a;
    a.require(5,7);
    auto b = cast(const(int)[int])a;
}

Probably hide the process behind a function to make it look more smooth; otherwise I'm outta ideas.

On Thursday, 29 July 2021 at 20:44:35 UTC, Elronnd wrote:

You aren't missing anything. It's a bug, and should be fixed, but that'll require making the frontend understand what require is (or providing a way to express this in a generic manner).