Singular programming

I am tweaking singular a bit,
I have a question,
What hapends if you try to cast a spell than does not exist in your class?

Code:

public static Composite CreateInterruptSpellCast(UnitSelectionDelegate onUnit)
        {
            return
                new Decorator(
                // If the target is casting, and can actually be interrupted, AND we've waited out the double-interrupt timer, then find something to interrupt with.
                    ret => onUnit != null && onUnit(ret) != null && onUnit(ret).IsCasting && onUnit(ret).CanInterruptCurrentSpellCast
                /* && PreventDoubleInterrupt*/,
                    new PrioritySelector(
                        Spell.Cast("Rebuke", onUnit),
                        Spell.Cast("Avenger's Shield", onUnit),
                        Spell.Cast("Hammer of Justice", onUnit),
		                       
                       

                        Spell.Cast("Kick", onUnit),
                        Spell.Cast("Gouge", onUnit, ret => !onUnit(ret).IsBoss() && !onUnit(ret).MeIsSafelyBehind), // Can't gouge bosses.

                        Spell.Cast("Counterspell", onUnit),

                        Spell.Cast("Wind Shear", onUnit),

                        Spell.Cast("Pummel", onUnit),

                        Spell.Cast("Spear Hand Strike", onUnit), 

                        // AOE interrupt
                        Spell.Cast("Disrupting Shout", onUnit),
                        // Gag Order only works on non-bosses due to it being a silence, not an interrupt!
                        Spell.Cast("Heroic Throw", onUnit, ret => TalentManager.IsSelected(7) && !onUnit(ret).IsBoss()),

                        Spell.Cast("Silence", onUnit),

                        Spell.Cast("Silencing Shot", onUnit),

                        // Can't stun most bosses. So use it on trash, etc.
                        Spell.Cast("Bash", onUnit, ret => !onUnit(ret).IsBoss()),
                        Spell.Cast("Skull Bash (Cat)", onUnit, ret => StyxWoW.Me.Shapeshift == ShapeshiftForm.Cat),
                        Spell.Cast("Skull Bash (Bear)", onUnit, ret => StyxWoW.Me.Shapeshift == ShapeshiftForm.Bear),
                        Spell.Cast("Mighty Bash", onUnit, ret => !onUnit(ret).IsBoss() && onUnit(ret).IsWithinMeleeRange ),
                        Spell.Cast("Solar Beam", onUnit, ret => StyxWoW.Me.Shapeshift == ShapeshiftForm.Moonkin),

                        Spell.Cast("Strangulate", onUnit),
                        Spell.Cast("Mind Freeze", onUnit),


                        // Racials last.
                        Spell.Cast("Arcane Torrent", onUnit),
                // Don't waste stomp on bosses. They can't be stunned 99% of the time!
                        Spell.Cast("War Stomp", onUnit, ret => !onUnit(ret).IsBoss() && onUnit(ret).Distance < 8),
                        Spell.Cast("Quaking Palm", onUnit)

                        ));
        }

Code above does not provide Wind Shear for shamans
when it is called in Elemental.cs with

Code:

 Helpers.Common.CreateInterruptSpellCast(ret => StyxWoW.Me.CurrentTarget),

 

u could test it by adding a non supported spell
but it should ignore it, cause singular checks with CanCast if a spell is castable and this should return false for the class (example: rebuke is a palaind spell not a shaman one)