June 2026 – Swift core library (swiftlang/swift) performance and stability highlights. Key features delivered and bugs fixed: - Fixed a circular reference in Codable synthesis when a property wrapper’s initializer references the enclosing type’s CodingKeys, eliminating a dependency cycle in the encoding/decoding pipeline. Commit: 2055bc3e7683415099e5f12d95fe151bd6f9b977. This ensures correct encoding/decoding for properties wrapped with the custom property wrapper and reduces fragile coupling between property wrappers and CodingKeys. - Added targeted tests for property wrappers with CodingKeys, covering five scenarios (simple wrappers, custom key mappings, mixed wrapped/unwrapped properties, Decodable-only, Encodable-only). These tests live in test/decl/protocol/special/coding/struct_codable_property_wrapper_codingkeys.swift. Validation and test results: - All existing Codable tests pass (74 tests). - Runtime encode/decode verified for the new scenarios. Impact and value: - Improves reliability of Codable synthesis for users employing property wrappers, reducing encoding/decoding edge-case failures. - Provides regression safety with focused test coverage, enabling safer refactors in the Codable synthesis path. Technologies/skills demonstrated: - Swift compiler internals (Codable synthesis path, ResolveCodingKeys), property wrappers, unit/regression testing, and rigorous test coverage.