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digitalmars.D.bugs - [Issue 7713] New: lambda inference doesn't work on template function argument

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7713

           Summary: lambda inference doesn't work on template function
                    argument
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: k.hara.pg gmail.com


--- Comment #0 from Kenji Hara <k.hara.pg gmail.com> 2012-03-15 01:58:13 PDT ---
test case:
----
void foo(T)(T delegate(in Object) dlg)
{}
void main()
{
    foo( (in obj) { return 15; } );   // line 6
}

output:
----
test.d(6): Error: template test.foo(T) does not match any function template
declaration
test.d(6): Error: template test.foo(T) cannot deduce template function from
argument types !()(void)

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next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7713


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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull


--- Comment #1 from Kenji Hara <k.hara.pg gmail.com> 2012-03-15 21:50:30 PDT ---
https://github.com/D-Programming-Language/dmd/pull/814

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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Alex Rønne Petersen <xtzgzorex gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |xtzgzorex gmail.com


--- Comment #2 from Alex Rønne Petersen <xtzgzorex gmail.com> 2012-03-15
21:56:53 PDT ---
Question: Would this also allow:

void foo(T)(T t, bool delegate(T) dg)
{
}

void main()
{
    foo(1, (i) { return true; });
}

or is it limited to the return type of the delegate (or is this completely
unrelated to this bug?)?

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--- Comment #3 from Kenji Hara <k.hara.pg gmail.com> 2012-03-15 22:49:51 PDT ---
(In reply to comment #2)

 Question: Would this also allow:
 
 void foo(T)(T t, bool delegate(T) dg)
 {
 }
 
 void main()
 {
     foo(1, (i) { return true; });
 }
 
 or is it limited to the return type of the delegate (or is this completely
 unrelated to this bug?)?


This is unrelated bug, and your sample is NEVER compiled.
Because each parameter type inference runs in *parallel*.

[1] T                is deduced from argument   1
 -> T is deduced to int, OK.
[2] bool delegate(T) is deduced from argument   (i) { return true; }
 -> Before template parameter type deduction, the delegate parameter i is
    deduced to T from template function parameter type, but T is not a
    real type.
    Then compiler cannot determine the delegate literal type.
[1] succeeded but [2] failed, so whole IFTI would fail.

The point is [1] and [2] runs in parallel, so they have no dependency.

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--- Comment #4 from Alex Rønne Petersen <xtzgzorex gmail.com> 2012-03-15
22:54:41 PDT ---
That makes sense. Thank you for the explanation.

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--- Comment #5 from github-bugzilla puremagic.com 2012-03-20 14:12:18 PDT ---
Commit pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/8dba679462b3ee58bb589aa7a6b28135191c09be
Merge pull request #814 from 9rnsr/fix7713

Issue 7713 - lambda inference doesn't work on template function argument

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prev sibling parent d-bugmail puremagic.com writes:
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Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla digitalmars.com
         Resolution|                            |FIXED


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