ReScript 12.0 Released with New Build System

"ReScript, the robustly typed language that compiles to JavaScript, has released ReScript 12.0, completing a multi-year development roadmap to modernize the compiler toolchain and deliver a better developer experience with improved syntax and performance. ReScript 12.0 introduces several major features, including a completely rewritten build system, improved operators, dictionary literals with pattern matching, nested record types, JSX preserve mode, and regex literals. The release also brings a modular runtime architecture and platform-specific binaries that significantly reduce installation footprint."

"One of the headline features in ReScript 12 is the new build system, introduced earlier in November, which brings intelligent dependency tracking and faster incremental builds. The system now tracks dependencies more precisely, avoids unnecessary recompilations, and integrates with incremental workflows even across monorepo packages. This addresses limitations that became apparent as projects grew larger and monorepos became more common, as the previous build system worked primarily on single package projects."

"ReScript 12 finalizes the unified operator work introduced earlier this year. Arithmetic operators such as +, -, *, /, % and ** now work consistently for int, float, and bigint, allowing the compiler to infer the correct specialization from the left operand. Developers can now use + for string concatenation as well, eliminating the need for the legacy +., -., *., and /. operators that were previously required for floating-point operations."

ReScript 12.0 completes a multi-year roadmap to modernize the compiler toolchain and improve developer experience with syntax and performance enhancements. The release includes a completely rewritten build system with intelligent dependency tracking, faster incremental builds, and better integration across monorepo packages. A legacy build command remains available for compatibility but is expected to be removed in v13. Unified operators now work consistently across int, float, bigint, and string concatenation, simplifying arithmetic and string operations. Dictionary literals compile to plain JavaScript objects and support pattern matching, reducing boilerplate. The release also introduces a modular runtime and platform-specific binaries to shrink installation footprint.

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