Hi Magnus,

You raise an excellent point.

The swift journey has been interesting to watch, for sure.  I do not believe 
anyone has ever started with a rigidly typed system and then tried to make it 
more dynamic (Java JVM dynamicInvocation work by Bracha notwithstanding).  
There have been several languages that started out as purely dynamic that then 
added optional type annotations to get compilers to be a little more helpful.  
Strongtalk, Objective C v1, etc.  But starting out with a rigid static bias and 
trying to add in dynamic features seems a lot harder than going the other way.

Anyhow, I have heard for years this argument about how helpful compilers are 
when there is abundant type information.

My experience leaves me personally skeptical but more to the point - where's 
the actual proof?

Here's a blog post with a lot of links to studies trying to assess whether 
static-type heavy systems actually reduce defects and make people more 

Don't just read the page, follow the links and read the studies.

This continues to be argued at YCombinator. 

And there is this discussion of a talk called "The unreasonable effectiveness 
of dynamic typing".

Bottom line - I want to see the proof too.  I think everything should be 
DynamicLookupable - especially library code since the library creator cannot 
know in advance how his code may be used and it may well want to be bridged 
from another environment but then I have been doing a lot of bridging of Pharo 
Smalltalk to native C libraries via FFI lately and I firmly believe bridges 
need to run both ways.

It is easy to bridge Objective C from Smalltalk.  Swift, OTOH, looks nigh 
impossible as it is.

> On Dec 4, 2017, at 10:20 AM, Magnus Ahltorp via swift-evolution 
> <swift-evolution@swift.org> wrote:
>> 5 Dec. 2017 01:08 Benjamin G via swift-evolution <swift-evolution@swift.org> 
>> wrote:
>> Unless DynamicLookup is used to circumvent every compiler warning or errors 
>> thrown at you by the language because your design is unsound. Something like 
>> "ho, yeah swift generics and protocols aren't really working fine together 
>> for your case, but just make everything DynamicLookupable and you'll be all 
>> set". Or "This JSON document has a really complex schema. Let's just not 
>> specify anything, and call the fields like this, you won't even feel any 
>> difference anyway".
> We have heard these horror tales about everyone making "everything 
> DynamicLookupable" and this being extremely bad, but can anyone actually 
> produce a believable example? It's not like it's absurdly convenient to 
> implement this, the ergonomics are at the call site, not the implementation. 
> It sounds like you think that just conforming to DynamicMemberLookupProtocol 
> and DynamicCallable will magically make everything in the code dynamic with 
> no extra effort.
> /Magnus
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