[Issue 17661] New isInputRange rejects valid input range

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=17661

--- Comment #2 from hsteoh at quickfur.ath.cx ---
Haha, I tried doing that but ran into another bug:

------
struct C {
    private S* impl;
}
struct S {
    bool empty;
    @property C front() return { return C(&this); }
    void popFront() { }

    pragma(msg, typeof((S r) return => r.front));
}
------

Compiler output (dmd -dip25 -dip1000):
------
test.d(10): Error: returning r.front() escapes a reference to parameter r,
perhaps annotate with return
_error_
------

Because of this, isInputRange still doesn't work, with your proposed change.

Apparently dmd fails to pick up the `return` annotation for some reason.  Which
is actually rather strange, because:

-------
pragma(msg, typeof((int* r) return => r));
-------

prints:

-------
int* function(return int* r) pure nothrow @nogc return @safe
-------

so obviously the syntax is correct, and at least some of the time dmd is able
to process it correctly.  I've no idea why it doesn't pick up the annotation
and/or process it correctly when in the first code snippet above.

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