Annotations import fails when imported in class scope

[felixmulder]

// Foo.scala
class Foo {
  import foo.Annot

  @Annot def foo = ()
}

// Annot.java
package foo;
import java.lang.annotation.*;

public @interface Annot {}

compiles with:

-- [E006] Unbound Identifier Error: local/test.scala ---------------------------
4 |  @Annot def foo = ()
  |   ^^^^^
  |   not found: type Annot

longer explanation available when compiling with `-explain`
-- Error: local/test.scala -----------------------------------------------------
2 |  import foo.Annot
  |         ^^^
  |         => Unit(Foo.this.foo) is not stable

whereas:

import foo.Annot
class Foo {
  @Annot def foo = ()
}

Compiles just fine.

[odersky]

This one might be unavoidable. Annotations in dotty have semantic meaning - they can rewrite the tree they annotate. This means we need to know what they are beforehand. There's an intricate dance when to look at what, which is unfortunately incompatible with the use pattern shown here.

[odersky]

We might want to revert the decision to evaluate annotations early. It will depend how our plans for meta programming shape up in general.

[smarter]

Already fixed, regression test in #5800.