[Issue 4895] New: isOutputRange is true for ranges which can't be output ranges

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=4895

           Summary: isOutputRange is true for ranges which can't be output
                    ranges
           Product: D
           Version: unspecified
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: major
          Priority: P2
         Component: Phobos
        AssignedTo: nobody at puremagic.com
        ReportedBy: jmdavisProg at gmx.com


--- Comment #0 from Jonathan M Davis <jmdavisProg at gmx.com> 2010-09-19 03:39:49 PDT ---
This compiles:

import std.range;

struct Range
{
    @property bool empty()
    {
        return true;
    }


    @property int front()
    {
        return 7;
    }


    void popFront()
    {
    }


    @property Range save()
    {
        return this;
    }
}

void main()
{
    static assert(isInputRange!(Range));
    static assert(isOutputRange!(Range, int));
}



It shouldn't. You can't ever assign to front. I believe that the problem is
that this portion of put() ends up being compiled in:

static if (is(typeof(r.front = e, r.popFront())))
{
    r.front = e;
    r.popFront();
}

since putting static assert(0); in that portion of put() causing the
compilation to fail.

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