For example, if I use UInt8 constant for if condition then only one branch is evaluated:
```sql
SELECT if(1, 'success', throwIf(1, 'Executing FALSE branch'))

┌─'success'─┐
│ success   │
└───────────┘

1 rows in set. Elapsed: 0.003 sec.
```

But if I use some constant expression, then both branches are evaluated:
```sql
SELECT if(empty(''), 'success', throwIf(1, 'Executing FALSE branch'))

0 rows in set. Elapsed: 0.003 sec.

Received exception from server (version 21.12.2):
Code: 395. DB::Exception: Received from localhost:9000. DB::Exception: Executing FALSE branch: While processing if(empty(''), 'success', throwIf(1, 'Executing FALSE branch')). (FUNCTION_THROW_IF_VALUE_IS_NON_ZERO)
```
{
public:
    static constexpr auto name = "if";
    static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionIf>(); }
private:
    template <typename T0, typename T1>
    static UInt32 decimalScale(const ColumnsWithTypeAndName & arguments [[maybe_unused]])
    {
        if constexpr (is_decimal<T0> && is_decimal<T1>)
        {
            UInt32 left_scale = getDecimalScale(*arguments[1].type);
            UInt32 right_scale = getDecimalScale(*arguments[2].type);
            if (left_scale != right_scale)
                throw Exception("Conditional functions with different Decimal scales", ErrorCodes::NOT_IMPLEMENTED);
            return left_scale;
        }
        else
            return std::numeric_limits<UInt32>::max();
    }
    template <typename T0, typename T1, typename ColVecT0, typename ColVecT1>
    ColumnPtr executeRightType(