Using a public PRNG and uniform distribution (C++17)

I am trying to implement a PRNG I found online yet I am having compile time issues (seen below):

1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.15.26726\include\xutility(4010): error C2061: syntax error: identifier 'result_type'
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.15.26726\include\xutility(4012): error C2065: '_Ty1': undeclared identifier
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.15.26726\include\xutility(4012): error C2065: '_Ty1': undeclared identifier
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.15.26726\include\xutility(4012): error C2923: 'std::conditional_t': '_Ty1' is not a valid template type argument for parameter '_Ty2'

This is my code:

std::random_device rd;
small_prng engine;
std::uniform_int_distribution< int > ud( 0, 50 );

for ( auto i = 0; i < 100; i++ ) {
    printf( "%i\n", ud( engine ) );
}

And this is the code I got online...

class small_prng {
    uint32_t a;
    uint32_t b;
    uint32_t c;
    uint32_t d;

    static inline uint32_t rot( uint32_t x, uint32_t k ) noexcept {
        return ( ( ( x ) << ( k ) ) | ( ( x ) >> ( 32 - ( k ) ) ) );
    }
public:
    using value_type = uint32_t;

    explicit small_prng( uint32_t seed = 0xdeadbeef ) noexcept {
        a = 0xf1ea5eed;
        b = c = d = seed;
        for ( size_t i = 0; i < 20; ++i )
            ( *this )( );
    }

    inline uint32_t operator()( ) noexcept {
        uint32_t e = a - rot( b, 27 );
        a = b ^ rot( c, 17 );
        b = c + d;
        c = d + e;
        d = e + a;
        return d;
    }
};

Is there any reason this isn't working? How come? Compiling using Visual Studio 2017.