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wire 2026-08-31
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Swift drops redundant array-index overflow check, Kotlin exposes boxed overrides

By RepoJournal · Filed · About Mobile platforms

engine-flutter-autoroll lucasly-ba abelkov ktoso slavapestov eeckstein
6 people shipped this
engine-flutter-autoroll @engine-flutter-autoroll 4 cited lucasly-ba @lucasly-ba 2 cited abelkov @abelkov 2 cited ktoso @ktoso slavapestov @slavapestov eeckstein @eeckstein

Swift's optimizer now skips an overflow check on array-index additions that can never observably overflow, while Kotlin's symbol light classes gain support for boxed methods on overrides in final classes.

Swift merged the first of two optimizations in #90824 [1] (and [2]): `x + c` (c > 0) used as an array index can't observably overflow, since an overflow makes the sum negative and the bounds check (`>= 0`) traps anyway. The redundant overflow check is dropped when the sum is later checked `< 0`, shrinking generated code for array access. Separately, two Kotlin commits [3] and [4] fix KT-88879: with `-Xjvm-expose-boxed`, symbol light classes did not generate a light method for an override in a final class when the signature mentions a value class, so Java calls to such methods were reported as unresolved despite valid JVM backend code. Overrides are now boxed and exposed. Three Flutter engine autoroll commits [5][6][8] advance Skia, and one [7] updates the Fuchsia Linux SDK; all are routine dependency rolls with no breakage reported.

Action items

References

  1. [1] [SILOptimizer] Drop the overflow check of an array-index addition ↗ apple/swift
  2. [2] [SILOptimizer] Drop the overflow check of an array-index addition ↗ apple/swift
  3. [3] [SLC] Expose boxed methods for overrides in final classes ↗ JetBrains/kotlin
  4. [4] [SLC] Extend JvmExposeBoxed tests for overrides ↗ JetBrains/kotlin
  5. [5] Roll Skia from 588b550a4dd8 to 24a8072e4046 (1 revision) (#192050) ↗ flutter/flutter
  6. [6] Roll Skia from 3ae8e3d1e335 to ce359c7fbfe6 (1 revision) (#192037) ↗ flutter/flutter
  7. [7] Roll Fuchsia Linux SDK from o9DikEfRoFyVK3LKD... to EPzxifoyt36b5qiBy... (#192048) ↗ flutter/flutter
  8. [8] Roll Skia from ce359c7fbfe6 to 588b550a4dd8 (1 revision) (#192040) ↗ flutter/flutter

$ ls mobile/reviews/ # the step-back reads

the week in review Flutter tool moves to constructor injection the month in review Swift and Flutter steady runtimes; Kotlin locks down builds
Topics: Mobile Full archive →

Quick answers

What shipped in Mobile platforms on August 31, 2026?
Swift's optimizer now skips an overflow check on array-index additions that can never observably overflow, while Kotlin's symbol light classes gain support for boxed methods on overrides in final classes. In total, 13 commits and 9 pull requests landed.
Who contributed to Mobile platforms on August 31, 2026?
6 developers shipped this update, including engine-flutter-autoroll, lucasly-ba, ktoso, slavapestov, eeckstein, and abelkov.
What were the notable Mobile platforms updates?
[SILOptimizer] Drop the overflow check of an array-index addition, [SILOptimizer] Drop the overflow check of an array-index addition, and [SLC] Expose boxed methods for overrides in final classes.
♥

$ log Mobile platforms --recent

Flutter engine rolls Skia and Fuchsia SDK 8 shipped Swift and Kotlin compiler fixes land, Flutter dependency rolls continue 30 shipped Swift's async runtime paves way for per-function CPU control and macro-driven conformance 156 shipped Flutter fixes semantics geometry, UTF-16 deletion, iOS keyboard accents 160 shipped

$ log --all # elsewhere on the wire

Meta React Native adds Stable API guards to renderer attributed string FastAPI & Pydantic Pydantic fixes Mypy plugin crash, tightens datetime constraints

$ ls showcases/

Rails Django Laravel Node.js Go Vercel Vue.js Kubernetes HashiCorp Arch Linux Linux Anthropic

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