In Swift, we lost this functionality. The reason this was traditionally done with a #define, and not a function or class, is so that we can use the __PRETTY_FUNCTION__, __FUNCTION__, __FILE__, and __LINE__ macros. The preprocessor replaces those macros with their actual values. For example, __FILE__ will always contain the filename where the macro is placed for example. If you were to use them in a logging function, the macros would always contain the information of the logging function, not the calling function, rendering them useless.

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How does this work when I said earlier that using __FUNCTION__ and its friends in a function only gives you the information in the function instead of where it’s called? Well, that’s the secret sauce I discovered last week. If you set the default value of a parameter in a function to one of the macros, the compiler fills in that value at the calling location giving us the effect we need. Giving us access to the correct macro values inside the function that’s called.

When you pass a function as an argument of a generic type <T>, Swift doesn’t pass its raw address directly, but a pointer to a trampoline function (see below) along with some meta information about the function. And the trampoline itself is a part of a structure wrapping the original function.

That the compiler is capable of catching (some) bugs using static type checks is undeniably true. However, what is also obviously true is that not all bugs are type errors (for example, most of the 25 top software errors don’t look like type errors to me, and neither goto fail; nor Heartbleed look like type errors either, and neither do the top errors in my different projects), so having the type-checker give our programs a clean bill of health does not make them bug free, it eliminates a certain type or class of bugs.

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[Robert Smallshire] talks about this some more in the talk titled The Unreasonable Effectiveness of Dynamic Typing, which I heartily recommend. However, this isn’t the only source, for example there was a study with the following title: An experiment about static and dynamic type systems: doubts about the positive impact of static type systems on development time (pdf), which found the following to be true in experiments: not only were development times significantly shorter on average with dynamically typed languages, so were debug times.