[whatwg] The Module Tag

 > > The sender is suspended until the receiver returns.

 > And what happens to the receiver? Is the script currently
 > running in the receiver context interrupted?

The send function checks the type of its argument. It then checks for the 
existence of the receive function. If it exists, it calls it, passing the 
argument. If it does not exist, it throws.

Send/receive is a guarded function invocation. It does not suspend, interrupt, 
queue, or block. It is just an invocation.