'type': sizeof cannot be applied to a type that contains 'auto'

The sizeof operator cannot be applied to the indicated type because it contains the auto specifier.

The following example yields C3540.

// C3540.cpp
// Compile with /Zc:auto
int main() {
    auto x = 123;
    sizeof(x);    // OK
    sizeof(auto); // C3540
    return 0;
}

auto Keyword
/Zc:auto (Deduce Variable Type)
sizeof Operator