import std.stdio, std.range, std.algorithm, std.traits, std.meta;

​

struct UNIFORM{ string name; }

​

struct A{

    int i1;

    @UNIFORM() int i2;

    @UNIFORM("fuzz") int i3;

    @UNIFORM int i4;

}

​

template getUDA(alias a, U){

  static if(hasUDA!(a, U)) enum getUDA = getUDAs!(a, U)[$-1];

                      else enum getUDA = U.init;

}

pragma(msg, getUDA!(A.i1, UNIFORM)); //UNIFORM(null)

pragma(msg, getUDA!(A.i2, UNIFORM)); //UNIFORM(null)

pragma(msg, getUDA!(A.i3, UNIFORM)); //UNIFORM("fuzz");

pragma(msg, getUDA!(A.i4, UNIFORM)); //Error: initializer must be an expression, not UNIFORM

​

struct UNIFORM2{ string name=""; }

struct B{ @UNIFORM2() int i1; }

​

pragma(msg, getUDA!(B.i1, UNIFORM2)); //UNIFORM("") instead if UNIFORM(null)

​