Can't use a macro annotation class as a normal type in the compilation unit it's defined in

[alexeyr]

I have a macro annotation with parameters: class AnnotationType(...) extends StaticAnnotation. Since c.prefix.tree in the macro implementation is the tree for the annotation constructor, I've tried
c.eval(c.Expr[AnnotationType](c.prefix.tree)) and c.eval(c.prefix.asInstanceOf[c.Expr[AnnotationType]].
The compiler complains that it can't expand AnnotationType even though it isn't used as an annotation and shouldn't be expanded. If this worked, it would simplify http://stackoverflow.com/questions/32631372/getting-parameters-from-scala-macro-annotation and http://stackoverflow.com/questions/37891855/macro-annotation-with-default-arguments.

[xeno-by]

This is a limitation of how macro annotation expansion is implemented for scalac.

I'd like to detect situations when a user forgot to enable the macro paradise plugin and, as a result, their annotations have spuriously failed to expand. There's the @compileTimeOnly annotation that can be used for this, but unfortunately it not only produces errors on usages of macro annotations in annotation positions, but also on any kind of usages.

A better mechanism to address the original issue may enable us to be more permissive wrt other kinds of usages of macro annotations.

[alexeyr]

Unfortunately, it doesn't work without @compileTimeOnly either.

[xeno-by]

That's because the paradise plugin automatically adds the @compileTimeOnly annotation to macro annotations.