Quoted expressions in annotations

[nicolasstucki]

@nicolasstucki The printing of the following program shows that the '{4} in the annotation is not reified during compilation:

import scala.quoted._

class annot[T: Type](x: Expr[T]) extends scala.annotation.Annotation

class Test()(implicit qtx: QuoteContext) {
  @annot('{4})
  def foo(str: String) = '{4}
}

I'm not sure if it's a bug or not, as annotations don't have runtime semantics.

Originally posted by @liufengyun in #7053 (comment)

[nicolasstucki]

We should disallow them

[nicolasstucki]

And this one #7053 (comment)

import scala.quoted._

class annot[T: Type](x: T) extends scala.annotation.Annotation

class Test()(implicit qtx: QuoteContext) {
  @annot(4)('[Int])
  def foo(str: String) = ()
}