$ javac -version
javac 11.0.3

@java.lang.annotation.Documented
@java.lang.annotation.Retention(java.lang.annotation.RetentionPolicy.CLASS)
@java.lang.annotation.Target(java.lang.annotation.ElementType.TYPE_USE)
@interface NonNull {
}

class Example {
    Object legacy() {
        return null;
    }

    Object example() {
        @NonNull Object o = legacy();
        return o;
    }
}

  java.lang.Object example();
    descriptor: ()Ljava/lang/Object;
    flags: (0x0000)
    Code:
      stack=1, locals=2, args_size=1
         0: aload_0
         1: invokevirtual #2                  // Method legacy:()Ljava/lang/Object;
         4: astore_1
         5: aload_1
         6: areturn
      LineNumberTable:
        line 13: 0
        line 14: 5
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       7     0  this   LExample;
            5       2     1     o   Ljava/lang/Object;
      RuntimeInvisibleTypeAnnotations:
        0: #18(): LOCAL_VARIABLE, {start_pc=5, length=2, index=1}
          NonNull

  java.lang.Object example();
    descriptor: ()Ljava/lang/Object;
    flags: (0x0000)
    Code:
      stack=4, locals=3, args_size=1
         0: ldc           #32                 // Dynamic #0:$jacocoData:Ljava/lang/Object;
         2: checkcast     #34                 // class "[Z"
         5: astore_1
         6: aload_0
         7: invokevirtual #2                  // Method legacy:()Ljava/lang/Object;
        10: astore_2
        11: aload_2
        12: aload_1
        13: iconst_2
        14: iconst_1
        15: bastore
        16: areturn
      LineNumberTable:
        line 13: 6
        line 14: 11
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            6      11     0  this   LExample;
           11       6     2     o   Ljava/lang/Object;
      RuntimeInvisibleTypeAnnotations:
        0: #18(): LOCAL_VARIABLE, {start_pc=11, length=6, index=1}
          NonNull