Structural directive with HostBinding should be a compiler warning

[valakis]

As far as my understanding about the structural directives goes, @HostBinding and friends will not work with them because it will attach them to the <template></template> in the background, which is pointless.

I believe the compiler should emit a warning in this case.

[jbdeboer]

I would prefer a compiler error instead of a warning. Warnings tend to be ignored.