Error "data did not match any variant of untagged enum ValueOrVec" when visiting a style rule with `border: none`

[lxsmnsyc]

Repro: https://lightningcss.dev/playground/index.html#%7B%22minify%22%3Atrue%2C%22nesting%22%3Atrue%2C%22customMedia%22%3Atrue%2C%22cssModules%22%3Afalse%2C%22analyzeDependencies%22%3Afalse%2C%22targets%22%3A%7B%22chrome%22%3A6225920%7D%2C%22source%22%3A%22%5Cn%20%20.toggle%20%7B%5Cn%20%20%20%20color%3A%20red%3B%5Cn%20%20%20%20border%3A%20none%3B%5Cn%20%20%7D%22%2C%22visitorEnabled%22%3Atrue%2C%22visitor%22%3A%22%7B%5Cn%20%20Rule(rule)%20%7B%5Cn%20%20%20%20if%20(rule.type%20%3D%3D%3D%20'style')%20%7B%5Cn%20%20%20%20%20%20return%20rule%5Cn%20%20%20%20%7D%5Cn%20%20%7D%5Cn%7D%22%2C%22unusedSymbols%22%3A%5B%5D%2C%22version%22%3A%22local%22%7D

For some reason, a style with border: none throws ERROR: data did not match any variant of untagged enum ValueOrVec on visitor even when untouched. Commenting border: none and the output works fine. I'm not sure which other properties has this behavior.

I'm trying to modify selectors but this issue, which is kinda unrelated to my goal, serves as a huge blocker.

Edit:
After experimenting a bit, it seems that border: none's AST is

{
  property: 'border',
  value: { width: { type: 'medium' }, style: 'none', color: 'currentcolor' }
}

whereas in the type definitions, currentcolor is defined as

export type CurrentColor = {
  type: "currentcolor";
};

so the correct output must be

{
  property: 'border',
  value: {
    width: {
      type: 'medium'
    },
    style: 'none',
    color: {
      type: 'currentcolor'
    }
  }
}

on the contrary, the color property is defined as a union of object types so it can never be string. The issue here is at the AST generation.