React Compiler Ported to Rust: Babel AST Compatibility and Flow Match Syntax Support
A technical update describes porting the React Compiler to Rust with fixes for Babel AST round-trip serialization and support for Flow's experimental match syntax. The work addresses JSON serialization issues where null predicates were being lost during round-trip conversions, and upgrades the parser to handle Flow match expressions. This matters because it improves the reliability of the compiler's AST handling and expands language feature support for Flow type checking.
The update details a Rust port of the React Compiler that resolves a critical issue in Babel AST deserialization: the parser emits `"predicate": null` to signal the absence of Flow `%checks` predicates, but standard JSON deserialization was collapsing both absent and explicit null values into `None`, causing round-trip failures. The fix applies a `nullable_value` deserializer to distinguish between absent fields (skipped on serialize), explicit nulls (round-tripped as `"predicate": null`), and populated predicates. Additionally, the update adds support for Flow's experimental match syntax by upgrading hermes-parser to version 0.28+ with the `enableExperimentalFlowMatchSyntax` flag, enabling parsing of six previously unsupported match fixtures. Testing shows all 1,782 round-trip tests passing and all 33 test suites green with zero failures.
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- Hacker NewsCenter
Port React Compiler to Rust
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