[ruby-core:65177] [ruby-trunk - Feature #9999] Type Annotations

Issue #9999 has been updated by Rory O’Kane.


One design to consider is interfaces as implemented in the Go programming language, in which interfaces combine static typing and duck typing (https://en.wikipedia.org/wiki/Duck_typing#In_Go). Go accomplishes this by counting any object as conforming to an interface as long as it responds to the required methods. The object’s type does not have to explicitly declare that it implements that interface, and it does not matter whether the interface was defined before or after the interface-implementing types were defined.

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Feature #9999: Type Annotations
https://bugs.ruby-lang.org/issues/9999#change-49016

* Author: Davide D'Agostino
* Status: Assigned
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* Category: 
* Target version: 
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Hi all,

I know @matz is interested in introducing **type annotations** in ruby. More here: https://bugs.ruby-lang.org/issues/5583

I think it's time for ruby to get this.

Before working on a patch I would like to know:

1. Syntax of methods signatures
2. Syntax of variables guards (?)
3. Implementation

For point **1** I was thinking in some like:

~~~ruby
def connect(r -> Stream, c -> Client) ->  Fiber
def connect(Stream r, Client c) -> Fiber # quite sure this will make some reduce problems in the grammar
~~~

Before making a proposal consider: keyword arguments and default value collisions.

Then for point **2** I'm not sure if we want also check assignments but as before a syntax could be:

~~~ruby
r: Client = something # will throw an exception if something is not kind of Client
~~~

Finally, **implementation**. Do we want some in python style and then leave the programmer/library for the implementation **or** (and I'm for this) we want MRI do that, if so how?

Cheers!
DD

p.s. Sorry if this issue was already discussed but I didn't find anything except the link posted.



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