// Can a be converted to b?

// score 0 = exact match

// score Int.MAX_VALUE = no match

// score 1 = conversion needed (boxing/unboxing or non-primitve widening)

// score -2 = primitive widening needed

static int typeConversionScore(Class a, Class b) {

  if (a == b) ret 0;

  if (b.isPrimitive()) {

    // target type is primitive

    if (a.isPrimitive()) {

      // both types are primitive

      // No widenings to bool

      if (b == bool.class) ret Int.MAX_VALUE;

      // No widenings to byte

      if (b == byte.class) ret Int.MAX_VALUE;

      // byte can be converted to char

      if (b == char.class) ret a == byte.class ? -2 : Int.MAX_VALUE;

      // byte can be converted to short

      if (b == short.class) ret a == byte.class ? -2 : Int.MAX_VALUE;

      // byte, char and short can be converted to int

      if (b == int.class) ret a == byte.class || a == char.class || a == short.class ? -2 : Int.MAX_VALUE;

      // byte, char, short and int can be converted to long

      if (b == long.class) ret a == byte.class || a == char.class || a == short.class || a == int.class ? -2 : Int.MAX_VALUE;

      // byte, char, short and int can be converted to float

      if (b == float.class) ret a == byte.class || a == char.class || a == short.class || a == int.class ? -2 : Int.MAX_VALUE;

      // all primitive types except bool can be converted to double

      ret a != bool.class ? -2 : Int.MAX_VALUE;

    } else {

      // source type is boxed - check if they're a match 

      ret primitiveToBoxedType(b) == a ?  1 : Int.MAX_VALUE;

    }

  } else {

    // Target type b is not primitive.

    // Object type a is primitive - check for exact match

    if (a.isPrimitive())

      ret primitiveToBoxedType(a) == b ? 1 : Int.MAX_VALUE;

    // BOTH TYPES ARE NOT PRIMITIVE.

    // if not assignable, no match

    if (!b.isAssignableFrom(a)) ret Int.MAX_VALUE;

    // if assignable, get precise score

    // if any is an interface, just get score 1

    if (a.isInterface() || b.isInterface()) ret 1;

    if (a.isArray() && b.isArray())

      ret typeConversionScore(a.getComponentType(), b.getComponentType())/2;

    // for classes, count subclass distance

    ret subclassDistance(a, b)*2;

  }

}