非命名空间范围内的显式特化不会在 GCC 中编译
以下代码在 Clang 中编译，但在 GCC 中不编译:
The following code compiles in Clang but does not in GCC:
template<typename T>
struct Widget
{
template<typename U>
void foo(U)
{
}
template<>
void foo(int*)
{
}
};
根据 C++ 标准([temp.expl.spec]，第 2 段):
According to the C++ standard ([temp.expl.spec], paragraph 2):
可以在任何范围内声明显式特化，其中相应的主模板可以定义
An explicit specialization may be declared in any scope in which the corresponding primary template may be defined
这是 GCC 中的错误吗?如果是，我如何在其错误跟踪器中找到它?
Is this a bug in GCC and if so how can I find it in its bug tracker?
这是 GCC 的输出:
This is GCC's output:
prog.cc:13:14: error: explicit specialization in non-namespace scope 'struct Widget<T>'
template<>
^
我使用的是 GCC HEAD 8.0.1，带有 -std=c++2a.
I'm using GCC HEAD 8.0.1, with -std=c++2a.
推荐答案
这应该是 GCC 错误.在任何范围内都应该允许完全特化，包括在类定义中.
This should be a GCC bug. Full specialization should be allowed in any scope, including in class definition.
根据 CWG 727，[temp.expl.spec] 第 2 段已更改为
According to CWG 727, [temp.expl.spec] paragraph 2 was changed from
(强调我的)
显式特化应在包含特化模板的命名空间中声明.声明符 id 或 class-head-name 未限定的显式特化应在模板的最近封闭命名空间中声明，或者，如果命名空间是内联的 (10.3.1 [namespace.def])，则应在其内部的任何命名空间中声明.封闭命名空间集.这样的声明也可以是定义.如果声明不是定义，则可以稍后定义特化(10.3.1.2 [namespace.memdef]).
An explicit specialization shall be declared in a namespace enclosing the specialized template. An explicit specialization whose declarator-id or class-head-name is not qualified shall be declared in the nearest enclosing namespace of the template, or, if the namespace is inline (10.3.1 [namespace.def]), any namespace from its enclosing namespace set. Such a declaration may also be a definition. If the declaration is not a definition, the specialization may be defined later (10.3.1.2 [namespace.memdef]).
到
(强调我的)
显式特化可以在任何范围内声明，其中可以定义相应的主模板(10.3.1.2 [namespace.memdef]、12.2 [class.mem]、17.6.2 [temp.mem]).
An explicit specialization may be declared in any scope in which the corresponding primary template may be defined (10.3.1.2 [namespace.memdef], 12.2 [class.mem], 17.6.2 [temp.mem]).
似乎 GCC 没有遵循这一点.
It seems GCC fails to follow this.
编辑
我已将该问题报告为错误 85282.
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