Should this Compile?

[SamwiseFilmore]

I've created toString() for a struct (which is a lot more 
complicated than what I've provided here) that returns a large 
number of concatenated strings. Here is the example:

struct Card {
     // Flesh out these enums appropriately
     CardSuit suit;
     CardValue value;
     Facing facing;

     string toString() {
         return
             this.value.toString() ~
             " of " ~
             this.suit.toString() ~
             this.suit == CardSuit.diamonds ? "" : "\t" ~
             "\tfacing " ~
             this.facing.toString();
     }
}

This code does not compile with this error message:
Error: incompatible types for ((toString(this.p_value) ~ " of " ~ 
toString(this.p_suit)) ~ (this.p_suit)): 'string' and 'CardSuit'

Am I using the ternary operator correctly here, or is this an 
issue with dmd? I'm using dmd v2.076.0.

This is the ideal way to implement this function, although I 
could do it other ways.