[Issue 21406] New: CatAssign wrong evaluation/load order at run-time

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21406

          Issue ID: 21406
           Summary: CatAssign wrong evaluation/load order at run-time
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: critical
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: ibuclaw at gdcproject.org

This test should pass, but currently doesn't.

---
auto cat11ret3(T)(ref T s)
{
    s ~= 11;
    return [3];
}

void main()
{
    static auto test1(int[] val) { val ~= cat11ret3(val); return val; }
    assert(test1([1]) == [1, 11, 3]);
    static assert(test1([1]) == [1, 11, 3]);

    static auto test2(int[] val) { val = val ~ cat11ret3(val); return val; }
    // FIXME: assert(test2([1]) == [1, 3]);
    static assert(test2([1]) == [1, 3]);

    static auto test3(int[] val) { (val ~= 7) ~= cat11ret3(val); return val; }
    assert(test3([2]) == [2, 7, 11, 3]);
    static assert(test3([2]) == [2, 7, 11, 3]);

    static auto test4(int[] val) { (val ~= cat11ret3(val)) ~= 7; return val; }
    assert(test4([2]) == [2, 11, 3, 7]);
    static assert(test4([2]) == [2, 11, 3, 7]);
}
---

1. test4 is blocked by issue 21403.

2. test2 is a FIXME as per runnable/evalorder.d
https://github.com/dlang/dmd/blob/4208bfc30170b5272bb611433234acfd9230a631/test/runnable/evalorder.d#L55-L57

3. This test should be added to runnable/evalorder.d once dmd is able to both
compile it, and it passes both CTFE and run-time asserts.

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