From: mail@...
Date: 2014-12-17T07:52:56+00:00
Subject: [ruby-core:66900] [ruby-trunk - Feature #9999] Type Annotations

Issue #9999 has been updated by gogo tanaka.


I'm not sure how type annotations, gradual type or something like that with Ruby is, but it worth thinking.

What I can say here now is not only class but also `method` can be annotated and typed `attr_accessor` is also worth thinking.

```ruby
def sum(x, y)
  x.to_i + y
end
```

then, x can be annotated as "something responding to `:to_i`" or "something responding to some methods which respond to `+`"


Typed `attr_accessor`

```ruby
attr_accessor name: String # can be annotated String(or NilClass ..?)

```

Just idea : (

----------------------------------------
Feature #9999: Type Annotations
https://bugs.ruby-lang.org/issues/9999#change-50450

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