after powering through a few hours of broken syntax highlighting i did some digging in VSCode and it looks like Swift 6.4 just stopped emitting highlights for identifiers. on top of that, highlighting for keywords seems to have fallen back to regex patterns, which are obviously unreliable.
ideally yes, the Swift Extension for VSCode would use SwiftSyntax to parse syntactical tokens and only apply the semantic layer for the tokens that need it, but that doesn’t seem to be implemented as far as i can tell. it just seems to be semantic-or-nothing.
likely related to: Wrong response to Semantic Tokens request in Swift 6.4 - #4 by dima_kozhinov , but this is in VSCode, so i’m not sure if the suggested workaround there is applicable.