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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



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



https://github.com/D-Programming-Language/dmd/pull/814

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


Alex Rønne Petersen <xtzgzorex gmail.com> changed:

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



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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prev sibling next sibling parent d-bugmail puremagic.com writes:
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 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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22:54:41 PDT ---
That makes sense. Thank you for the explanation.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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Commit pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/8dba679462b3ee58bb589aa7a6b28135191c09be


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

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Mar 20 2012
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7713


Walter Bright <bugzilla digitalmars.com> changed:

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


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