Why TypeScript picked Go over Rust for its new compiler

Developers replaced the old JavaScript-based compiler with a native Go port to preserve exact compiler semantics and avoid a full rewrite. The existing compiler assumed garbage collection, so a Rust port would have required rearchitecting code for Rust’s borrow checker and ownership model, not just translating logic. A concrete example contrasts Go, which allows taking a pointer to a slice element and later appending (the GC keeps the old array alive), with Rust, which rejects the same pattern because an immutable borrow prevents the mutable push. That mismatch would have forced widespread changes to maintain memory safety, creating a much larger project than a port.

Go met the practical constraints: it supports garbage collection, enabled a port that preserves behavior, and offered robust native code generation and shared-memory concurrency across platforms. The move delivered substantial runtime benefits - announced as a 10x faster native TypeScript 7 - along with lower compile times and improved aggregate memory usage. The decision prioritized preserving compatibility and achieving significant performance gains with less disruptive engineering effort, trading Rust’s memory-safety guarantees for a faster, lower-effort path to a mature native compiler.