Valhalla basic concepts / terminology

[Brian Goetz]

FWIW, one of the things that made this take so long is that there are a 
number of related dichotomies, which we kept trying to collapse together 
(or use the wrong one):

  - primitive type vs reference type
  - primitive vs class
  - inline class vs identity class
  - pass/store by reference vs pass/store by value
  - nullable vs non-nullable
  - direct vs indirect





On 6/10/2020 11:20 AM, Dan Smith wrote:
>> On Jun 9, 2020, at 6:00 PM, Brian Goetz <brian.goetz at oracle.com> wrote:
>>
>>> - The syntax ".val" used to denote an "inline type" is a bit of a mismatch. Maybe we want a new syntax. Or maybe we want to rework the word "value" into the story so that "inline type" becomes "value type".
>>>
>>> This was my reaction too. ".val" means "the value itself, that you care about", and ".ref" means "a reference value that points to the value you care about", but I used the word "value" more times in the second phrase. It doesn't feel like this will be clear.
>> My intention here was to appeal to terms many users already understand: pass by value and pass by reference.  That's why `V.val` is not `V.inline`.
> Sure. And maybe that value/reference dichotomy can be extended into the terms we use in the model. So, the "values" of the language (using the term formally) are *values* (objects) and *references to values*. Now there's a nice alignment between the syntax and the terminology.
>
> Or given that "objects" parenthetical, maybe "object" is the right term: the values of the language are *objects* and *references to objects*. In that case, maybe the syntax should be 'Foo.obj'. The objects themselves, not references.

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