Strange compile error Clang vs GCC

run

$ clang -c test.cpp; gcc -c test.cpp

test.cpp:10:7: error: read-only variable is not assignable
    x = 0;
    ~ ^
test.cpp:26:7: note: in instantiation of member function 'A<float>::f' requested here
    a.f(0);
      ^
1 error generated.

test.cpp

template <typename T>
struct A
{
    void f(const int);
};

template <typename T>
void A<T>::f(int x)
{
    x = 0;
}

struct B
{
    void f(const int);
};

void B::f(int x)
{
    x = 0;
}

void f()
{
    A<float> a;
    a.f(0);

    B b;
    b.f(0);
}