Comment by patrec

It works through the fact that I specified "runtime" function ;)

A bit after that quote I have a note about `inline` functions in Zig, where I mention that they perform semantic inlining, which means dependencies triggered by the function actually get associated with the call site. Well, `comptime` function calls work just the same way---in fact, to the compiler, `comptime` calls are almost exactly identical to `inline` calls. So when we encounter a comptime function call, we start analyzing the ZIR for that function's body, but we don't switch our analysis unit, so comptime stuff doesn't really complicate the dependency graph at all (aside from the fact that it means you can depend on any number of source code hashes, instead of everything depending on exactly one).

With all that being said, there actually is a (completely unrelated) way in Zig to can depend on the body of a runtime function (hence why the quote includes "at least in the simplified view I'm presenting here"). It's to do with "inferred error sets" (IESes for short). If a function's return type is written `!T`, that means it can return an error, but we're asking the compiler to figure out exactly which errors are possible. So if at some point we need to know that set of errors (e.g. because the user has done some reflection to try and access the list of errors), that's where we get a dependency on a runtime function body, because we need to analyze the function body to learn about all the places it might return an error.