[css-values-5] Resolve first-valid() at parse time

[cdoublev]

The current definition says:

If none of the arguments represent a valid value for the property, the property is invalid at computed-value time.

But in the discussion before the resolution to add first-valid():

This would go away at parse time?

Correct.

And in a comment before:

When does it resolve?

Parse time. [...]

What if all values are invalid?

[...]

.foo { display: grid; display: first-supported(foo; bar); }

If it's resolved at parse time in standard properties, and all specified values are invalid, is the declaration dropped, producing display: grid? Or display becomes invalid at computed-value time?

Parse failure.

This discussion/comment happened before the commit adding first-valid(), so forgive me if I am missing other discussions and if the current text is intentional.

If not, does "go away at parse time" mean it should serialize with the first valid value?

When validating at parse time, the value for a "manual" fallback, for UAs that do not support first-valid(), is not required as an argument of first-valid():

div {
  /* validation at computed value time */
  color: red; /* for UAs that do not support first-valid() */
  color: first-valid(unsupported-color-name, red);
  /* validation at parse time */
  color: red; /* for UAs that do not support first-valid() */
  color: first-valid(unsupported-color-name);
}