Feature: C# Style Attributes

[danielcirket]

Something to consider, in C# you have the [Obsolete] attribute which can produce compiler errors if the IsError flag is set.

I should investigate the possibility of allowing custom attributes to generate warnings / errors from the compiler rather than just special case the built-in/standard libraray attributes

Edit, another thing to investigate: https://twitter.com/Nick_Craver/status/882961135401656320

[danielcirket]

Implemented in syntax parser as per #6