Input codes which should generate an error:

TEST 1:

 null + 3 -

TEST 2:

 if number? then true

TEST 3:

 1 * 2 -

TEST 4:

 * 3 + 4

TEST 5:

 5;

TEST 6:

 f(a,b,^);

TEST 7:

 -

TEST 8:

 8*8;

TEST 9;

 f[5]

TEST 10:

 f(,x)
 
 
TEST 11:
 
 f g
 
 
TEST 12:
 
 if let x:= 3 in y then true else false