Bugs in JShellState#drop

[Robert Field]

On 05/08/15 07:07, andrei.eremeev wrote:
> Hi REPL team,
>
> Bugs (see DropTest()):
> 1. 'x' has outcome 'Added'. In this case 'x' should have id which is 
> greater than id of 'y'. But 'x' does not.
> -> int x
> |  Added variable x of type int
>
> -> /- x
>
> -> int y
> |  Added variable y of type int
>
> -> int x
> |  Added variable x of type int
>
> -> /l
>
>    9 : int x;
>   10 : int y;

When the key is dropped, it still exists as a key.  So, I think the 
current behavior is correct.  But, I'm not sure.  I could see that in 
some cases that would be surprising.

>
> 2. Commands /var, /classes, /methods and JShellState#vars(), 
> JShellState#methods(), JShellState#classes return dropped keys.

Yep. Added to TODO (local) will fix soon.

>
> 3. Class with a broken (dropped) reference can be initiated and used.
> -> int x
> |  Added variable x of type int
>
> -> class A { int f() { return x; } }
> |  Added class A
>
> -> /- x
> |  Caused failure of dependent A --
> |      cannot find symbol
> |        symbol:   variable x
> |      class A { int f() { return x; } }
> |                                 ^
>
> -> new A().f()
> |  Expression value is: 0
> |    assigned to temporary variable $1 of type int

This is a case of needing class corralling.

>
>
> BTW, are we going to implement forward references for classes?
> Defining classes which refer to classes, methods or variables which 
> have not defined.

Yes, that needs class corralling too.

> E.g.
>   class A extends B {}
>   class B {}

We will not support forward reference of methods or classes where the 
signature is undefined.  For a class, the signature includes the name, 
the extends, implements, generic signature, types/names of fields, 
name/parameter-type of methods/constructors.  What can have forward 
references is method bodies and field initializers.  Note that we will 
attempt to corral classes whose signatures break after definition, but 
I'm not sure the level with which that can be achieved.  We the JEP for 
more detail on this.


-Robert

>
> Andrei Eremeev