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digitalmars.D.bugs - [Issue 9423] New: Missed conversion of lambda literal with ref argument

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9423

           Summary: Missed conversion of lambda literal with ref argument
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc


--- Comment #0 from bearophile_hugs eml.cc 2013-01-29 02:51:30 PST ---
void foo(int delegate(ref int[1]) spam) {}
void main() {
    foo((ref int[1] x) => 0); // OK
    foo(x => 0); // Error
}



DMD 2.062alpha gives:

test.d(4): Error: function test.foo (int delegate(ref int[1u]) spam)(null) is
not callable using argument types (void)
test.d(4): Error: cannot implicitly convert expression (__lambda3) of type int
delegate(int[1u] x) pure nothrow  safe to int delegate(ref int[1u])

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next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=9423


Kenji Hara <k.hara.pg gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull
           Platform|x86                         |All
         OS/Version|Windows                     |All
           Severity|normal                      |enhancement


--- Comment #1 from Kenji Hara <k.hara.pg gmail.com> 2013-01-29 09:23:54 PST ---
When I fixed bug7705, I decided that lambda inference does not infer parameter
storage classes. Instead, users should specify `ref`/`out`/`lazy` explicitly.

https://github.com/D-Programming-Language/dmd/pull/809/files#L1R496

Because, explicit specifying of `ref` in call site is sometimes required in
newsgroup.

void foo(ref int x) {}
int n;
foo(ref n);   // not allowed in today

So, current behavior is intended. You should write it as follows:

void foo(int delegate(ref int[1]) spam) {}
void main() {
    foo((ref x) => 0); // OK
}

However, I cannot say clearly whether it's right behavior.
I think that the opinion "parameter storage classes should be inferred" is also
worth.

Therefore, I'll mark this as 'enhancement'.

=====

A pull to implement this feature:
https://github.com/D-Programming-Language/dmd/pull/1580

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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--- Comment #2 from bearophile_hugs eml.cc 2013-01-29 10:00:15 PST ---
(In reply to comment #1)

 Therefore, I'll mark this as 'enhancement'.
 
 =====
 
 A pull to implement this feature:
 https://github.com/D-Programming-Language/dmd/pull/1580

Thank you Hara. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
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prev sibling parent d-bugmail puremagic.com writes:
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--- Comment #3 from bearophile_hugs eml.cc 2013-01-30 10:26:15 PST ---
A discussion thread, the answers are mixed:

http://forum.dlang.org/thread/mixmakdqfmaznmmnizux forum.dlang.org


A comment from Timon Gehr:

 BTW, the pull does not contain a test for the case
 
 void foo(int delegate(int) dg){ ... }     // 1
 void foo(int delegate(ref int) dg){ ... } // 2
 
 void main(){ foo(x=>0); } // call 1

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