Some code is not highlighted correctly

[Jason Orendorff]

Some folks noticed that GitHub's code highlighting for Rust recently regressed. Some examples are

• not highlighting async as a keyword in

  pub async fn foo() {}

• highlighting the two match arms differently in

  impl Lower {
      pub fn lower(&self, stmt: &Stmt) {
          match &stmt.node {
              RawStmt::Read(e) => self.lower_read(e),
              RawStmt::Print { expr, kind, newline, } => self.lower_print(expr, *kind, *newline),
          }
      }
  }

The cause of the regression is that GitHub recently switched from Linguist to tree-sitter-rust for Rust code highlighting.

The first bug is a one-liner in queries/highlights.scm. The second bug is more complicated. Part of it is due to handling (identifier) and (scoped_identifier) but not (type_identifier) and (scoped_type_identifier), but after that, it's probably impossible to distinguish names of struct-like enum variants from names of structs in (struct_pattern) using this pattern language. So whether we highlight them as enum variants (which would be correct in this example) or as type names, we'll be wrong sometimes.

[Alona Enraght-Moony]

For future reference, here's what these look like now:

[Max Brunsfeld]

/cc @patrickt @dcreager