[Issue 20943] New: std.algorithm.setops.cartesianProduct fails for ranges with @system popFront

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20943

          Issue ID: 20943
           Summary: std.algorithm.setops.cartesianProduct fails for ranges
                    with @system popFront
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: regression
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: john.loughran.colvin at gmail.com

unittest
{
    import std.algorithm : cartesianProduct;
    import std.algorithm : equal;
    import std.typecons : tuple;

    static struct SystemRange
    {
        int[] data;

        int front() @system @property
        {
            return data[0];
        }

        bool empty() @system @property
        {
            return data.length == 0;
        }

        void popFront() @system
        {
            data = data[1 .. $];
        }

        SystemRange save() @system
        {
            return this;
        }
    }

    assert(SystemRange([1, 2]).cartesianProduct(SystemRange([3, 4]))
        .equal([tuple(1, 3), tuple(1, 4), tuple(2, 3), tuple(2, 4)]));
}

/dlang/dmd/linux/bin64/../../src/phobos/std/algorithm/setops.d(398): Error:
scope variable r assigned to non-scope parameter this calling
onlineapp.__unittest_L1_C1.SystemRange.popFront
/dlang/dmd/linux/bin64/../../src/phobos/std/algorithm/setops.d(399): Error:
scope variable r assigned to non-scope parameter this calling
onlineapp.__unittest_L1_C1.SystemRange.empty
/dlang/dmd/linux/bin64/../../src/phobos/std/algorithm/setops.d(404): Error:
scope variable this assigned to non-scope parameter this calling
onlineapp.__unittest_L1_C1.SystemRange.save
/dlang/dmd/linux/bin64/../../src/phobos/std/algorithm/setops.d(398): Error:
scope variable r assigned to non-scope parameter this calling
onlineapp.__unittest_L1_C1.SystemRange.popFront
/dlang/dmd/linux/bin64/../../src/phobos/std/algorithm/setops.d(399): Error:
scope variable r assigned to non-scope parameter this calling
onlineapp.__unittest_L1_C1.SystemRange.empty
onlineapp.d(32): Error: template instance
std.algorithm.setops.cartesianProduct!(SystemRange, SystemRange) error
instantiating

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