/// A compressed span.
///
-/// `SpanData` is 12 bytes, which is a bit too big to stick everywhere. `Span`
+/// Whereas [`SpanData`] is 12 bytes, which is a bit too big to stick everywhere, `Span`
/// is a form that only takes up 8 bytes, with less space for the length and
/// context. The vast majority (99.9%+) of `SpanData` instances will fit within
/// those 8 bytes; any `SpanData` whose fields don't fit into a `Span` are
/// - `base` is 32 bits in both `Span` and `SpanData`, which means that `base`
/// values never cause interning. The number of bits needed for `base`
/// depends on the crate size. 32 bits allows up to 4 GiB of code in a crate.
-/// `script-servo` is the largest crate in `rustc-perf`, requiring 26 bits
-/// for some spans.
/// - `len` is 15 bits in `Span` (a u16, minus 1 bit for the tag) and 32 bits
/// in `SpanData`, which means that large `len` values will cause interning.
/// The number of bits needed for `len` does not depend on the crate size.
-/// The most common number of bits for `len` are 0--7, with a peak usually at
-/// 3 or 4, and then it drops off quickly from 8 onwards. 15 bits is enough
+/// The most common numbers of bits for `len` are from 0 to 7, with a peak usually
+/// at 3 or 4, and then it drops off quickly from 8 onwards. 15 bits is enough
/// for 99.99%+ of cases, but larger values (sometimes 20+ bits) might occur
/// dozens of times in a typical crate.
/// - `ctxt` is 16 bits in `Span` and 32 bits in `SpanData`, which means that