[Issue 13571] New: Overload of std.range.tee which accepts a functions does not accept structs or classes with opCall

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13571

          Issue ID: 13571
           Summary: Overload of std.range.tee which accepts a functions
                    does not accept structs or classes with opCall
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: DMD
          Assignee: nobody at puremagic.com
          Reporter: monkeyworks12 at hotmail.com

The following code does not work currently with tee:

struct Callable
{
    void opCall(int n)
    {
        writeln(n);
    }
}

void main()
{
    auto ints = [1, 2, 3];
    //Error
    auto res = ints.tee!Callable;
}

Note that the following code *does* work:

struct Callable
{
    void opCall(int n)
    {
        writeln(n);
    }
}

void main()
{
    Callable callable;
    auto ints = [1, 2, 3];
    auto r = ints.tee(callable);
        foreach (_; r) {} //Prints 1 2 3
}

So I don't know how useful adding support for doing `tee!Callable` would be.

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