Assorted macro/rust-analyzer woes

[davidbarsky]

I noticed a few issues with Salsa's macro that impact the accuracy of rust-analyzer's semantic highlighting. While the syntax theme that I'm using has support for semantic highlighting (so there's more bandwidth for the syntax highlighting to look slightly off), I confirmed the weirdness using a VS Code command called "Developer: Inspect Editor Tokens and Scopes" to determine just exactly how slightly off the different tokens are. Using tests/is_send_sync.rs as an example:

1. The struct keyword in struct MyInput, struct MyTracked<'db>, and struct MyInterned<'db> is reported as function, not a keyword.
   a. The lifetimes in the tracked and interned structs are reported as functions, not lifetimes.
   b. the field named field on MyInput is reported to be variable, not a property.
   c. The fields on MyTracked and MyInterned are reported to be methods, not fields. Arguably, this is the correct decision!
2. the tracked function fn test(db: &dyn Database, input: MyInput)'s name ("test") is reported as a struct, not a function.

In tests/input_field_durability.rs on struct MyInput, the field types (bool and usize) are reported as unresolved references, not primitives.

I think it'd be good to resolve these either in Salsa or rust-analyzer since it's part of Salsa's fit-and-finish and these token mismatches might larger, more subtle issues in how rust-analyzer handles Salsa.

On the plus side, go-to-def/find-references on Salsa-annotated functions and structs work!

[nikomatsakis]

Yes, I've noticed this. Presumably we need to adjust our spans somewhat.