This has some surprising behavior if `unsafe_sql?` returns false:

```
1.9.3-p392 :001 > def test(arg)
1.9.3-p392 :002?>   return y if y = arg
1.9.3-p392 :003?>   end
 => nil 
1.9.3-p392 :004 > test false
 => nil 
1.9.3-p392 :005 > test true
NameError: undefined local variable or method `y' for main:Object
	from (irb):2:in `test'
	from (irb):5
	from /home/justin/.rvm/rubies/ruby-1.9.3-p392/bin/irb:16:in `<main>'
```

Apparently this situation is not covered in the tests.