ADDITIONAL SYSTEM INFORMATION :
openjdk 23 2024-09-17
OpenJDK Runtime Environment Corretto-23.0.0.37.1 (build 23+37-FR)
OpenJDK 64-Bit Server VM Corretto-23.0.0.37.1 (build 23+37-FR, mixed mode, sharing)

A DESCRIPTION OF THE PROBLEM :
TypeMirror's documentation says that a the result of a toString() should try to be valid to use in source code.



    /**
     * Returns an informative string representation of this type. If
     * possible, the string should be of a form suitable for
     * representing this type in source code. Any names embedded in
     * the result are qualified if possible.
     *
     * @return a string representation of this type
     */

JDK-8281238 Solved this for the case of a single annotation. So now if we have

```
@Example String name;
```

The TypeMirror will give

```
java.lang.@Example String
```

But with multiple we get

```
java.lang.@A,@B String
```

Which is invalid. You would expect `java.lang.@A @B String`


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Make two annotations whose target is TYPE_USE

@Target({ElementType.TYPE_USE})
@interface ExampleAnn {}

@Target({ElementType.TYPE_USE})
@interface Other {}

2. Write some code which uses those annotation on a field type

class Example {
    @ExampleAnn @Other String abc;
}

3. Obtain a TypeMirror of the VariableElement via an annotation processor.

4. Using .toString() on that TypeMirror


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
java.lang.@ExampleAnn @Other String
ACTUAL -
java.lang@ExampleAnn,@Other String

FREQUENCY : always