Sergej Jaskiewicz
Software Engineer at JetBrains
Amsterdam, North Holland, Netherlands
Summary
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RockstarSergej Jaskiewicz is a software engineer based in Amsterdam with a decade of experience focusing on compiler and back-end development. Currently a compiler developer at Kotlin, he contributes to language code generation, JS interoperability, and improves debug and source map support for generated code. His open-source work includes making core reactive primitives thread-safe in OpenCombine and implementing/testing foundational serialization features in Swift's Foundation, demonstrating attention to correctness and cross-platform concerns. He brings strong testing and documentation habits—adding XCTest coverage and doc comments—to complex systems that demand reliability. Comfortable working across languages and runtimes, Sergej blends low-level compiler work with practical engineering tasks that improve developer experience. An often-overlooked strength is his knack for resolving subtle name-clash and codegen issues that surface only in real-world interop scenarios.
10 years of coding experience
Github Skills (13)
kotlin10
swift10
javascript10
code-generation10
foundation-sites10
multithreading10
concurrency10
foundation10
xctest10
documentation9
test-automation9
sourcemaps9
unit-testing9
Programming languages (17)
Github contributions (5)
OpenCombine/OpenCombine
Jun 2019 - Nov 2022
Open source implementation of Apple's Combine framework for processing values over time.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:15 releases, 39 reviews, 397 commits in 3 years 6 months
Contributions summary:Sergej primarily worked on implementing core functionality and ensuring thread-safety for the OpenCombine library, which provides an open-source implementation of Apple's Combine framework. Their commits focused on making the `PassthroughSubject` and `CurrentValueSubject` thread-safe. They also added tests for the core Combine constructs like `AnySubscriber`, `AnyPublisher`, `Subscribers.Assign`, `Subscribers.Sink`, `Publishers.ReplaceError`, and various operator specializations.
maccatalystioscombinereactive-programmingmacos
swiftlang/swift-corelibs-foundation
Jan 2017 - Dec 2019
The Foundation Project, providing core utilities, internationalization, and OS independence
Role in this project:Back-end Developer & Test Automation Engineer
Back-end Developer & Test Automation EngineerContributions:10 commits, 8 PRs, 22 comments in 2 years 11 months
Contributions summary:Sergej primarily focused on implementing and testing core Foundation framework features, specifically related to `NSKeyedArchiver`. They implemented the `init()` and `encodedData` methods within `NSKeyedArchiver`. The user also created and implemented test coverage for these new methods using `XCTest`. Furthermore, the user added documentation comments for several key Foundation classes and protocols.
tvostranslationinternationalizationfoundationindependence
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