Custom attributes are not treated as a first-class concept

[dsaf]

Custom attributes are a very special (underappreciated) language construct. The fact that they are classes is merely an implementation detail.

They can be:

• selectively applied to specific language elements;
• allowed (or not) to be applied multiple times;
• inherited;
• overriden.

[System.AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]

Action items:

1. create a separate kind of tooltip for attributes: "attribute ..."
2. present fundamental attribute information in a nice way:
   • target(s);
   • multiplicity;
   • inheritability;
   • whether it overrides an inherited attribute.
3. improve the e.g. "(class) ..." tooltip to show:
   • inherited attributes;
   • inherited but overridden attributes (ideally the difference, but it could be hard).
4. always show the inherited custom attributes as a gray font overlay.

PS: is QuickInfo the Roslyn's term for this kind of tooltips?

[dsaf]

It seems that custom attributes are becoming a major feature of Type Script as well:

http://blogs.msdn.com/b/typescript/archive/2015/03/05/angular-2-0-built-on-typescript.aspx

Time to properly support them in IDE across all languages.

https://twitter.com/ahejlsberg/status/532579556155482112

[dsaf]

An example of useful information not being shown:

None of targets, multiplicity, inheritability are shown:

[dsaf]

Inspiration:

https://github.com/MrJul/ReSharper.EnhancedTooltip