[Issue 17661] New isInputRange rejects valid input range

[d-bugmail--- via Digitalmars-d-bugs]

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

--- Comment #10 from github-bugzi...@puremagic.com ---
Commits pushed to dmd-cxx at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/be9ad6a311a53e9ab8d2a8b69777b73d33b279c3
Fix issue 17661: isInputRange should work with .front that returns reference to
parameter.

https://github.com/dlang/phobos/commit/6b460ab71750ae4d405ec392581d781a7d4f4e2a
Merge pull request #5688 from quickfur/issue17661

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[Issue 17661] New isInputRange rejects valid input range

[via Digitalmars-d-bugs]

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

--- Comment #9 from github-bugzi...@puremagic.com ---
Commits pushed to stable at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/be9ad6a311a53e9ab8d2a8b69777b73d33b279c3
Fix issue 17661: isInputRange should work with .front that returns reference to
parameter.

https://github.com/dlang/phobos/commit/6b460ab71750ae4d405ec392581d781a7d4f4e2a
Merge pull request #5688 from quickfur/issue17661

--

[Issue 17661] New isInputRange rejects valid input range

[via Digitalmars-d-bugs]

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

github-bugzi...@puremagic.com changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 Resolution|--- |FIXED

--

[Issue 17661] New isInputRange rejects valid input range

[via Digitalmars-d-bugs]

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

--- Comment #8 from github-bugzi...@puremagic.com ---
Commits pushed to master at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/be9ad6a311a53e9ab8d2a8b69777b73d33b279c3
Fix issue 17661: isInputRange should work with .front that returns reference to
parameter.

https://github.com/dlang/phobos/commit/6b460ab71750ae4d405ec392581d781a7d4f4e2a
Merge pull request #5688 from quickfur/issue17661

Issue 17661: isInputRange should accept .front that returns reference to range
merged-on-behalf-of: Petar Kirov 

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[Issue 17661] New isInputRange rejects valid input range

[via Digitalmars-d-bugs]

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

--- Comment #7 from hst...@quickfur.ath.cx ---
According to what Martin Nowak just said, there is no dmd bug, is that right? 
So we only need to fix Phobos.

--

[Issue 17661] New isInputRange rejects valid input range

[via Digitalmars-d-bugs]

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

hst...@quickfur.ath.cx changed:

   What|Removed |Added

   Keywords||pull

--- Comment #6 from hst...@quickfur.ath.cx ---
https://github.com/dlang/phobos/pull/5688

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[Issue 17661] New isInputRange rejects valid input range

[via Digitalmars-d-bugs]

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

Martin Nowak  changed:

   What|Removed |Added

 CC||c...@dawg.eu

--- Comment #5 from Martin Nowak  ---
Well in, (R r) return => r.front, the return applies to the delegate context,
but you're escaping a reference to the argument.
What you want to check is `(return ref R r) => r.front`.

Also rewriting your front methods to a free functions helps understanding.

  C front(return ref S _this) { return C(&_this); }

Obviously allowing

  (R r) => front(r)

would return a dangling reference to the value parameter.

NB, if your front methods leaked a field of the range (e.g. a pointer), you'd
need a `return scope` front methods, but the `(R r) => r.front` check is fine,
since the parameter `r` isn't scoped, i.e. it might leak any pointer fields.

--

[Issue 17661] New isInputRange rejects valid input range

[via Digitalmars-d-bugs]

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

--- Comment #4 from Andrei Alexandrescu  ---
hsteoh, could you please submit those as a separate bug report for dmd and
create a phobos PR using the simplest workaround you can find? That PR would
close this bug, and the other bug will be for the compiler. Thanks!

--

[Issue 17661] New isInputRange rejects valid input range

[via Digitalmars-d-bugs]

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

Steven Schveighoffer  changed:

   What|Removed |Added

 CC||schvei...@yahoo.com

--- Comment #3 from Steven Schveighoffer  ---
(In reply to Andrei Alexandrescu from comment #1)
> is(typeof((R r) => r.front)) || is(typeof((R r) return => r.front))


I'm new to the "return" annotation, but is that right? I mean, I thought return
was supposed to be an annotation on the parameter, not the function itself
(which in this case is actually not a member function).

I would have expected:

(return R r) => r.front

--

[Issue 17661] New isInputRange rejects valid input range

[via Digitalmars-d-bugs]

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

Vladimir Panteleev  changed:

   What|Removed |Added

   Hardware|x86_64  |All
 OS|Linux   |All

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[Issue 17661] New isInputRange rejects valid input range

[via Digitalmars-d-bugs]

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

--- Comment #2 from hst...@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(); }
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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[Issue 17661] New isInputRange rejects valid input range

[via Digitalmars-d-bugs]

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

Andrei Alexandrescu  changed:

   What|Removed |Added

 CC||and...@erdani.com

--- Comment #1 from Andrei Alexandrescu  ---
Can you try replacing the clause is(typeof((R r) => r.front)) with 

is(typeof((R r) => r.front)) || is(typeof((R r) return => r.front))

?

If that works you may want to create a PR with it. Thanks!

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