[Issue 24348] New: Inaccurate documentation for hasSlicing with infinite range

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24348

          Issue ID: 24348
           Summary: Inaccurate documentation for hasSlicing with infinite
                    range
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: snarwin+bugzilla at gmail.com

The documentation for std.range.hasSlicing states the following:

> For infinite ranges, when not using opDollar, the result of opSlice must be
> the result of take or takeExactly on the original range (they both return the
> same type for infinite ranges).

However, this is not true. The following program, which violates the above
rule, compiles without errors:

---
struct InfZeros
{
    enum empty = false;
    int front() => 0;
    void popFront() {}
    auto save() => this;

    auto opIndex(size_t[2] bounds)
    {
        size_t i = bounds[0], j = bounds[1];
        size_t length = i <= j ? j - i : 0;
        return Slice(length);
    }

    size_t[2] opSlice(size_t dim : 0)(size_t i, size_t j) => [i, j];
}

struct Slice
{
    size_t length;
    bool empty() => length == 0;
    int front() => 0;
    void popFront() { --length; }
    auto save() => this;
}

unittest
{
    import std.range.primitives;
    static assert(hasSlicing!InfZeros);
}
---

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