Compiler reverses annotation order?

Compiler
1

I noticed that if I have:

class foo(arg: Int) extends scala.annotation.StaticAnnotation
@foo(1)
@foo(2)
val x = 0

If I print the trees, the compiler shows the annotations in reverse order.
Is this considered a bug or are there no guarantees of annotation order?

2

This came up in ClassfileParser.

This commit on Scala 2 says

Preserve annotation order although not meaningful.

That compromises performance as a concession to DX. It was an old question.

Scala 3 prepends on symbol.addAnnotation (which was the previous Scala 2 behavior).

The @nowarn annotation, which is sensitive to ordering, uses source positions for that purpose.

1 Like