[css-values-5] A more complete syntax definition for `calc-size()` to also cover the `size` keyword

[romainmenke]

Current definition is:

<calc-size()> = calc-size( <calc-size-basis>, <calc-sum> )

<calc-size-basis> = [ <size-keyword> | <calc-size()> | any | <calc-sum> ]

And in prose:

Within the calc-size calculation, if the calc-size basis is not any, the keyword size is allowed. This keyword is a <length>, and resolves at used value time.

---

If I am reading the spec correctly we could also define the syntax as:

<calc-size()> = calc-size( [ [ <calc-size-basis> , [ <calc-sum> | size ] ] | [ any , <calc-sum> ] ] )

<calc-size-basis> = [ <size-keyword> | <calc-size()> | <calc-sum> ]

[cdoublev]

I think you missed that "within the calculation" means as a <calc-keyword> produced by <calc-sum>, like in --foo: calc-size(min-content, size + 20px) (borrowed from the non-normative note about nesting calc-size()).

[romainmenke]

I didn't miss that, but was thinking of this case: calc-size(min-content, size).

If size were part of the syntax definition for at least some of the cases then we can do more in Stylelint.

At the same time I also still want to be able to express which keywords are valid in calculations :)