c++ - Double template<> in template specialization -

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why code below compile? not specializing template member function of template class, 1 template<> should used. however, g++ compiles no warnings whatsoever, clang++ gives warning

warning: extraneous template parameter list in template specialization

template<typename t> struct s{};  template<> template<> // why can this?  struct s<int>{};  int main() {  }

because grammar allows it, , there doesn't seem under template specialization section prohibits it:

from [gram.temp]

explicit-specialization:

template < > declaration

from [gram.dcl]

declaration:

[...]

explicit-specialization

the fact grammar lax has been in active issues list (#293) since 2001.


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