'Auto can only be used for template function arguments' what?

[Mehrdad]

On Wednesday, 27 June 2012 at 03:54:12 UTC, Jonathan M Davis 
wrote:
> That isn't legal. auto ref can only be used with templated 
> functions.
>
> - Jonathan M Davis


The trouble is, distinguishing between when it should be illegal 
seems like a blur to me.

Consider all the cases like:

- <Regular method>
- <Mixin method>
- <Template method>
- Lambdas (in all forms)
- Template class, <regular method>
- Template class, <template method>
- Regular class, <template method>
- Regular class, template method, <mixin method>
- Regular class, regular method, <mixin method>
- Template class, regular method, <mixin method>
- <Templates inside mixins>
- yada yada



It becomes a *nightmare* to try to get everything right, when 
you're dealing with templates and mixins. And you run into bugs 
like this.

Why not just allow 'auto ref' for every function type?