Swift if directive quirk - swift

Question

Suppose I have a complex chain of ifs. Now I want to be sure that one of the conditions are triggered, so I add the final line to notify me when nothing was triggered.
if condition1 ...
else if condition2 ...
else if condition3 ...
else print( "Ooops nothing triggered" )
Since I only want to print this in DEBUG mode, I wrap the final line
#if DEBUG
else print( "Ooops nothing triggered" )
#endif
and I get the strangest errors. "Closure expression is unused" and "Expected expression".
Here is some simple working code to illustrate with.
let x = Int ( arc4random_uniform ( 100 ) ) - 50
// This works
if x > 0 { print ( "Positive" ) }
else if x < 0 { print ( "Negative" ) }
else { print ( "Oops - neither" ) }
// After adding the #if this does not compile
if x > 0 { print ( "Positive" ) }
else if x < 0 { print ( "Negative" ) }
#if DEBUG
else { print ( "Oops - neither" ) }
#endif
Obviously Swift's conditional compilation here fails. I wonder why and ask how to to do this so that the test is only applied in DEBUG mode?
FWIW I am not interested in e.g. using switch - the actual logic is complex. How to do this with ifs and else ifs if possible please?

Answer 1

These #ifs don't really work like those preprocessor directives in C. They
According to the grammar, the syntax of these directives are the following:
if-directive-clause → if-directive compilation-condition statements(opt)
elseif-directive-clauses → elseif-directive-clause elseif-directive-clauses(opt)
elseif-directive-clause → elseif-directive compilation-condition statements(opt)
else-directive-clause → else-directive statements(opt)
if-directive → #if
elseif-directive → #elseif
else-directive → #else
endif-directive → #endif
Note that an if-directive-clause consists of #if, then a compilation-condition, then some statements. Not just anything, but statements.
else { print ( "Oops - neither" ) }
is not a statement (or a list of statements).
How about putting the #if inside the else block? That is guaranteed to be a statements:
if x > 0 { print ( "Positive" ) }
else if x < 0 { print ( "Negative" ) }
else {
#if DEBUG
print ( "Oops - neither" )
#endif
}