[tel]

Of course you understand this, but for the benefit of the audience:

HM can do this because it dramatically restricts the allowable complexity of every single name in the program. This is rarely a problem, though, as typically you, as a programmer, only ever intend for names in the program to be so complex. The result is that HM simply ensures that your program is one which makes enough sense all of the time.

Which is sometimes painful for people when they first start.