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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - defaulted class template parameters dropped when rededucing template template parameter"
href="http://llvm.org/bugs/show_bug.cgi?id=22601">22601</a>
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<tr>
<th>Summary</th>
<td>defaulted class template parameters dropped when rededucing template template parameter
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>C++11
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>eniebler@boost.org
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The following code compiles successfully with gcc and fails with clang. I
honestly don't know for certain who is right here, but I would really like gcc
to be right.
template<typename...> struct list;
template<template<typename...> class A>
struct wrap
{
template<typename X, typename T = wrap>
struct impl;
template<typename...X, template<typename...> class D>
struct impl<list<X...>, wrap<D>>
{
using type = D<X...>;
};
template<typename...T>
using apply = typename impl<list<T...>>::type;
};
template<typename A, typename B> struct L;
template<typename A, typename B = void> struct L {};
int main()
{
wrap<L>::apply<int> s;
}
The error clang gives is:
test.cpp:15:18: error: too few template arguments for class template 'L'
using type = D<X...>;
^
test.cpp:18:3: note: in instantiation of template class
'wrap<L>::impl<list<int>, wrap<L> >' requested here
using apply = typename impl<list<T...>>::type;
^
test.cpp:28:12: note: in instantiation of template type alias 'apply' requested
here
wrap<L>::apply<int> s;
^
test.cpp:23:41: note: template is declared here
template<typename A, typename B> struct L;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
1 error generated.</pre>
</div>
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