Java annotations are not applied correctly classes defined within traits

[stringbean]

There are some edge cases for the targeting of annotations using the meta-annotations where they are not getting applied correctly for classes defined within traits.

According to the scaladocs for scala.annotation.meta:

The target meta-annotations can be put on the annotation type when instantiating the annotation. In the following example, the annotation @Id will be added only to the bean getter getX.

import javax.persistence.Id
class A {
  @(Id @beanGetter) @BeanProperty val x = 0
}

When the meta-annotations are used on classes defined in standalone compilation units or within objects everything behaves correctly. If the annotations are applied to classes defined within traits they get applied to extra methods that shouldn't be. In Scala 2.11.12 and below this only affected a couple of scenarios but in 2.12.0 and newer the behaviour has regressed significantly.

I've created a test harness that applies the different meta-annotations and outputs where the annotations were actually applied. The harness can be found in this gist.

A summary of the results can be seen below:

Test Case	Expected	2.11	2.12	2.13
TestBean.defaultTarget	C	C	C	C
TestBean.fieldTarget	F	F	F	F
TestBean.getterTarget	M	M	M	M
TestBean.beanPropertyDefault	C	C	C	C
TestBean.beanPropertyField	F	F	F	F
TestBean.beanPropertyGetter	M	M	M	M
TestBean.beanPropertyBeanGetter	B	B	B	B
WrappedBean.defaultTarget	C	-	M	M
WrappedBean.fieldTarget	F	F	FMC	FMC
WrappedBean.getterTarget	M	M	M	M
WrappedBean.beanPropertyDefault	C	-	MB	MB
WrappedBean.beanPropertyField	F	FC	FMCB	FMCB
WrappedBean.beanPropertyGetter	M	MC	MC	MC
WrappedBean.beanPropertyBeanGetter	B	B	B	B

Key:

• C: constructor
• F: field
• M: getter method
• B: bean getter method

[SethTisue]

(not sure if the situation is any different or better in Scala 3)