From: Jean Privat <jean@pryen.org>
Date: Wed, 23 Jul 2014 18:22:52 +0000 (-0400)
Subject: Merge: Add annotation `fixed` for virtual types
X-Git-Tag: v0.6.7~23
X-Git-Url: http://nitlanguage.org

Merge: Add annotation `fixed` for virtual types

Fixed virtual types prevent redefinition is subclasses

~~~
class A
   type F: Foo is fixed
end
class B
   super A
   redef type F: Foo # Static error
end
~~~

Currently, there is no really apparent benefit of fixed virtual types because the hack of `typing::check_subtype`. Thus this is only a step toward the resolution of #298.

Note: the first commits introduce the basic verification on redefinitons of virtual types that is missing; but nobody saw that there was no checks.

Pull-Request: #611
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
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1f67b392d1ab94a5285c291ee534bff65b6e0933