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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 --- - Error when explicitly specify template parameters for variadic template function that uses variadic arguments in return type specification"
href="http://llvm.org/bugs/show_bug.cgi?id=22588">22588</a>
</td>
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<tr>
<th>Summary</th>
<td>Error when explicitly specify template parameters for variadic template function that uses variadic arguments in return type specification
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>3.5
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<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>yyc1992@gmail.com
</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>Created <span class=""><a href="attachment.cgi?id=13864" name="attach_13864" title="source file">attachment 13864</a> <a href="attachment.cgi?id=13864&action=edit" title="source file">[details]</a></span>
source file
Might be related to 22191 but at least the symptom is different.
Source file that produces the error (Also attached).
```
#include <utility>
#include <functional>
template<typename Func, typename... Args>
static inline auto
caller(Func &&func, Args&&... args)
-> decltype(func(std::forward<Args>(args)...))
// Changes to `-> void` suppresses the error
{
return func(std::forward<Args>(args)...);
}
template<typename Func, typename... Args>
static inline auto
wrapper(Func &&func, Args&&... args)
-> decltype(caller(std::forward<Func>(func),
std::forward<Args>(args)...))
{
return caller<Func, Args...>(std::forward<Func>(func),
std::forward<Args>(args)...);
}
int
main()
{
wrapper([] () {}); // OK
wrapper([] (void*) {}, nullptr); // Error on Clang 3.5.1
return 0;
}
```
Error message produced on Clang 3.5.1
```
main2.cpp:18:12: error: no matching function for call to 'caller'
return caller<Func, Args...>(std::forward<Func>(func),
^~~~~~~~~~~~~~~~~~~~~
main2.cpp:26:5: note: in instantiation of function template specialization
'wrapper<(lambda at main2.cpp:26:13), nullptr_t>' requested here
wrapper([] (void*) {}, nullptr);
^
main2.cpp:6:1: note: candidate template ignored: substitution failure [with
Func =
(lambda at main2.cpp:26:13), Args = <nullptr_t>]: pack expansion contains
parameter packs 'Args' and 'args' that have different lengths (1 vs. 2)
caller(Func &&func, Args&&... args)
^
1 error generated.
```
GCC 4.9.2 compiles it without an error.</pre>
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