Error messages like 'List<@Nullable String> cannot be assigned to ...' can be confusing, because the annotations (e.g. @Nullable) do not affect Java's type system. It might be clearer to omit the annotations when printing types in diagnostics.

===
import static java.lang.annotation.ElementType.TYPE_USE;

import java.lang.annotation.Target;
import java.util.List;

@Target(TYPE_USE)
@interface A {}

public class T {
  List<@A Number> f(List<String> xs) {
    return xs;
  }
}
===

Actual:

$ javac -fullversion ~/T.java
javac full version "19-ea+33-2224"
T.java:11: error: incompatible types: List<String> cannot be converted to List<@A Number>
    return xs;
           ^
1 error

Suggested:

error: incompatible types: List<String> cannot be converted to List<Number>