Dynamic SOQL + var binding

gistfile1.cls

Set<String> names = new Set<String>{'Me','Myself','I'};
String query = 'SELECT id, name FROM User WHERE LastName IN :names';
List<sObject> objs = Database.query(query);  
System.debug(objs);

How is this possible? That set variable is private and the query variable is just a String. I believe you, but this makes no sense.

A coworker wrote it and I was reviewing his code. My conclusion is that this is some form of black magic.

Or a more serious answer: Database.query must use some reflection-like magic under the hood to find any variable mentioned that's in scope at the time of the query and load it in.

Voodoo if you ask me ;) Technically it's an interpreted language right? No idea how it works with byte code though.

Actually, the platform now complies to Java bytecode. This is a fairly recent change.