angular/angular.js — pull request #2713 by JensRantil (2013-05-20 16:53:09+00:00)
Title: Doc: Compile function returns post-link function

Judging from source code[1], if a compile function (within a directive)
returns a function, it is a post-link function.

[1] https://github.com/angular/angular.js/blob/master/src/ng/compile.js#L709