reduce calls to attr.span() in old doc attr parsing
r? `@oli-obk`
should be trivial, can also delegate to `@GuillaumeGomez` or `@JonathanBrouwer.`
As part of making span() return an option I want to reduce the number of places we call span in without it being known what specific attr it's for. This makes that more obvious for doc. Part of a chain of PRs that's coming.
https://github.com/rust-lang/rust/issues/131229#issuecomment-3395316064