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digitalmars.D.bugs - [Issue 6613] New: Can't use empty tuple as default value for variadic template function parameter

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6613

           Summary: Can't use empty tuple as default value for variadic
                    template function parameter
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: minor
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: thecybershadow gmail.com


--- Comment #0 from Vladimir Panteleev <thecybershadow gmail.com> 2011-09-06
12:40:19 PDT ---
template Tuple(T...) { alias T Tuple; }

void f(T...)(int arg0 = 0, T argN = Tuple!());

static this() { f(); }

Compiler output:
test.d(3): Error: cannot implicitly convert expression (tuple()) of type () to
()
test.d(5): Error: template instance test.f!() error instantiating

The compiler requires a default value for argN, because it comes after another
optional argument, but it doesn't seem like an empty tuple can be specified.

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parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6613


Andrej Mitrovic <andrej.mitrovich gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |andrej.mitrovich gmail.com,
                   |                            |k.hara.pg gmail.com


--- Comment #1 from Andrej Mitrovic <andrej.mitrovich gmail.com> 2013-02-08
18:01:40 PST ---
[internal note]: It seems Tuple!() is treated as a type when it's a default
argument (at least ExpInitializer::semantic seems to think so). But as a
variable initializer it works ok:

template Tuple(T...) { alias T Tuple; }
void main()
{
    Tuple!() t = Tuple!();
}

CC'ing Kenji since he might be interested in this bug.

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