Karoy Lorentey c46afaf068
rdar://105027055: Improve AttributedString view slicing (#92)
* rdar://105027055: Do not use as-casts in specializations.

Introduce _specializingCast and use it instead of `as?`-casts inside
if ladders that implement generic specialization.

`as?` invokes undesirable runtime machinery such as bridging checks.

* rdar://105027055: Ensure AttributedString views have properly aligned bounds

* rdar://105027055: Implement index(_:offsetBy:limitedBy:) in AttributedString views
2023-05-08 11:17:35 -07:00
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