Is this like Facebook's Static Hermes?

[Please-just-dont]

Static Hermes uses Typescript types to compile to native. Has anyone heard of it? Is this similar? In what ways is it different?

[ASDAlexander77]

Similar goal, very different design.

What they share: both use TypeScript type annotations to produce fast native code ahead of time instead of interpreting or JIT-ing JavaScript.

Where they differ:

	Static Hermes	tslang
Starting point	A JavaScript engine (Hermes). Typed code gets faster native code, but the whole JS runtime and its semantics stay underneath, so untyped JS still runs.	A compiler with no JS engine at all. TypeScript is lowered through MLIR to LLVM IR and on to a native executable, an object file, a DLL/.so, WebAssembly, or run straight away by the built-in JIT.
TypeScript	Converted to Flow first. Types are made "sound": checked casts are inserted where untyped values flow into typed code. Some TS features are ruled out by design.	TypeScript is the source language itself. Types decide the native layout directly: number is a double, classes are structs with vtables, and int/i32/i64/char and similar are available for exact-width code. any and unions are boxed or tagged values, with run-time checks when they're cast to a concrete type.
Memory	Hermes's garbage collector.	Your choice per build, -mm=gc | rc | none | own: Boehm GC (default), reference counting, never freeing, or single ownership inferred at compile time, like Rust's borrow checker.
Runtime / libraries	The Hermes runtime, mainly aimed at React Native.	A small runtime plus a default library of JS built-ins (Array, Map, Set, String, RegExp, Date, Promise/async, fetch, …). No Node or browser APIs.
Native interop	Through the engine's APIs.	Direct C calls via declare function (or headers turned into declarations with tsbindgen). .ts files can be compiled with --emit=obj and linked into C/C++ projects through CMake. See native_ts_graphics, which drives a C++ D3D12/Vulkan renderer from TypeScript.
Targets	Wherever Hermes runs.	Windows, Linux, Android (arm64-v8a, armeabi-v7a, x86_64) and wasm32.

In short: Static Hermes is "JavaScript, made faster where you add types". tslang is "TypeScript as a systems language": closer to compiling C# or Swift than to running JS. The trade-off is that tslang supports a subset of the dynamic JavaScript world (no eval, no npm packages that rely on Node, and so on), while Static Hermes keeps full JS compatibility.