Make segment range type split safe.

This allows for use in restricted contexts.

Updates #5039

PiperOrigin-RevId: 351265378

pkg/segment/range.go

@@ -30,27 +30,37 @@ type Range struct {
 
 // WellFormed returns true if r.Start <= r.End. All other methods on a Range
 // require that the Range is well-formed.
+//
+//go:nosplit
 func (r Range) WellFormed() bool {
 	return r.Start <= r.End
 }
 
 // Length returns the length of the range.
+//
+//go:nosplit
 func (r Range) Length() T {
 	return r.End - r.Start
 }
 
 // Contains returns true if r contains x.
+//
+//go:nosplit
 func (r Range) Contains(x T) bool {
 	return r.Start <= x && x < r.End
 }
 
 // Overlaps returns true if r and r2 overlap.
+//
+//go:nosplit
 func (r Range) Overlaps(r2 Range) bool {
 	return r.Start < r2.End && r2.Start < r.End
 }
 
 // IsSupersetOf returns true if r is a superset of r2; that is, the range r2 is
 // contained within r.
+//
+//go:nosplit
 func (r Range) IsSupersetOf(r2 Range) bool {
 	return r.Start <= r2.Start && r.End >= r2.End
 }
@@ -58,6 +68,8 @@ func (r Range) IsSupersetOf(r2 Range) bool {
 // Intersect returns a range consisting of the intersection between r and r2.
 // If r and r2 do not overlap, Intersect returns a range with unspecified
 // bounds, but for which Length() == 0.
+//
+//go:nosplit
 func (r Range) Intersect(r2 Range) Range {
 	if r.Start < r2.Start {
 		r.Start = r2.Start
@@ -74,6 +86,8 @@ func (r Range) Intersect(r2 Range) Range {
 // CanSplitAt returns true if it is legal to split a segment spanning the range
 // r at x; that is, splitting at x would produce two ranges, both of which have
 // non-zero length.
+//
+//go:nosplit
 func (r Range) CanSplitAt(x T) bool {
 	return r.Contains(x) && r.Start < x
 }