Bug 39653

Summary:	[C++0x] error referencing a more specialized variadic template from primary
Product:	gcc	Reporter:	Martin Sebor <msebor>
Component:	c++	Assignee:	Not yet assigned to anyone <unassigned>
Status:	RESOLVED FIXED
Severity:	normal	CC:	andreas.milton.m, fang, gcc-bugs, jason, tiago
Priority:	P3
Version:	4.5.0
Target Milestone:	4.7.0
Host:		Target:
Build:		Known to work:
Known to fail:		Last reconfirmed:
Bug Depends on:	35722
Bug Blocks:

Description Martin Sebor 2009-04-05 17:11:16 UTC

I believe the following program is well-formed but gcc rejects it with
the same error as the one discussed in bug 35722. I'm opening this as
a separate bug since unlike in bug 35722, the referenced template is
variadic.

$ cat t.C && g++ --version && g++ -std=c++0x t.C
template <class T, class ...Types>
struct S {
    typedef typename S<Types...>::type type;
};

template <class T>
struct S<T> { typedef T type; };
g++ (GCC) 4.5.0 20090404 (experimental)
Copyright (C) 2009 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

t.C:3: sorry, unimplemented: cannot expand ‘Types ...’ into a fixed-length argument list

Comment 1 Jason Merrill 2009-04-05 19:35:27 UTC

I'd write that as

template <class... Types>
struct S;

template <class T, class ...Types>
struct S<T, Types...> {
    typedef typename S<Types...>::type type;
};

template <class T>
struct S<T> { typedef T type; };

Comment 2 Jonathan Wakely 2010-10-18 12:06:55 UTC

*** Bug 46061 has been marked as a duplicate of this bug. ***

Comment 3 Jason Merrill 2011-10-03 00:26:27 UTC

Fixed by the patch for bug 35722.