This is a patch release with the following minor improvements:

• BigString sometimes miscounted distances in its character view, resulting in an invalid collection conformance. This is now fixed. (#485)
• BigString's Unicode Scalar and character views now make better use of known lengths of the text chunks stored in the tree, resulting in significantly improved performance for their distance measurements. (#486)
• The Foundation-specific toolchain configuration was updated to include the Deque type. (#496)

What's Changed

• [BigString] Fix character indexing operations by @lorentey in https://github.com/apple/swift-collections/pull/485
• [BigString] Harvest some low-hanging performance fruit by @lorentey in https://github.com/apple/swift-collections/pull/486
• Include DequeModule in the Foundation toolchain build by @cthielen in https://github.com/apple/swift-collections/pull/496

Full Changelog: https://github.com/apple/swift-collections/compare/1.2.0...1.2.1