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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Alias template produces seemingly bogus "template template argument has different template parameters" error"
href="https://bugs.llvm.org/show_bug.cgi?id=37157">37157</a>
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<th>Summary</th>
<td>Alias template produces seemingly bogus "template template argument has different template parameters" error
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>arthur.j.odwyer@gmail.com
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<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>I (and also GCC 7.0-and-later) claim that this program is legal C++.
template<template<class> class X> struct A {};
template<template<class...> class Y> using B = A<Y>;
template<class> struct S;
B<S> b;
Clang, on the other hand, bails out at line 2:
prog.cc:2:50: error: template template argument has different template
parameters than its corresponding template template parameter
template<template<class...> class Y> using B = A<Y>;
^
prog.cc:2:19: note: template type parameter pack does not match template type
parameter in template argument
template<template<class...> class Y> using B = A<Y>;
^
prog.cc:1:19: note: previous template type parameter declared here
template<template<class> class X> struct A {};
^
Clang becomes happy if I change it from 'using B = A<Y>' to 'struct B {}', and
then sad again if I change it to 'struct B : A<Y> {}'.</pre>
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