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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - A bug for template specialization"
href="https://bugs.llvm.org/show_bug.cgi?id=43496">43496</a>
</td>
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<tr>
<th>Summary</th>
<td>A bug for template specialization
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>8.0
</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>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>C++17
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>liwei.cpp@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
</td>
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<p>
<div>
<pre>The code is as follows:
#include <type_traits>
template <typename> class AddLayer;
template <template <typename> class TLayer>
struct LayerInputPortSet
{
using type = int;
};
template <>
struct LayerInputPortSet<AddLayer>
{
using type = float;
};
using type1 = typename LayerInputPortSet<AddLayer>::type;
static_assert(std::is_same_v<type1, float>);
template <template<typename> class TLayer>
struct Sublayer
{
template <typename TInputs>
using LayerType = TLayer<TInputs>;
};
using type = typename LayerInputPortSet<Sublayer<AddLayer>::template
LayerType>::type;
static_assert(std::is_same_v<type, float>);
When compiling (with -std=c++17), type1 == float, but with the introduction of
a wrapper (Sublayer), type != float. In fact, the compiler thought that type is
int.
A similar issue is as follows:
#include <type_traits>
template <typename> class AddLayer;
template <template <typename> class TLayer>
struct LayerInputPortSet;
template <>
struct LayerInputPortSet<AddLayer>
{
using type = float;
};
using type1 = typename LayerInputPortSet<AddLayer>::type;
static_assert(std::is_same_v<type1, float>);
template <template<typename> class TLayer>
struct Sublayer
{
template <typename TInputs>
using LayerType = TLayer<TInputs>;
};
using type = typename LayerInputPortSet<Sublayer<AddLayer>::template
LayerType>::type;
static_assert(std::is_same_v<type, float>);
When compiling, the compiler reports that
implicit instantiation of undefined template
'LayerInputPortSet<Sublayer<AddLayer>::template LayerType>'
This bug happened on clang++ 6, 7, 8.</pre>
</div>
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