[css-properties-values-api] Typed custom property declarations are syntax-checked at computed-value time, not parse time.

[jyc]

Clarify that the syntax field is used during computed-value time,
write in the section about calculation of computed values that
declarations can be found invalid at computed-value time, and update the
example which previously indicated syntax-checking at parse time.

Per Seattle resolution, as expressed in the following comments:

The original issue (should a property fail at parse-time if a typed
custom property is used in a wrong way, per the property's grammar) is,
I think, a no. I believe this falls out of our decision at the Seattle
f2f (#354) that registering a custom property shouldn't require an
immediate global re-parse. You can do wrong things to/with a typed
custom property; it'll just cause a failure at computed-value time, like
an untyped custom property with an incompatible value does.

• [css-properties-values-api] Substituting registered properties with var() #321 (comment)

Further clarification: per Seattle resolution, when using a typed
property in a stylesheet, setting to an invalid value doesn't trigger
fallback ...

• [css-properties-and-values] Setting/registering is allowed to be order-dependent #354 (comment)

[dholbert]

@tabatkins , perhaps you could review this pull request (or suggest another Properties & Values spec-editor to review it)?

[andruud]

@tabatkins @jyc I think this is resolved by 8dfc2d9 , close?

[tabatkins]

Yup, thanks!