#typescript.mbt

#Parser Scope

• Declarations: function, class (lowered), let/const/var (with types)
• Statements: block, if, while, do/while (lowered), for, for-of, for-in (parsed as for-of), break/continue, return, throw, try/catch/finally, switch
• Expressions: literals, variables, unary/binary/ternary, new, calls, property/index access, assignments, arrow functions, function expressions, arrays/objects, yield, await
• Types: number, int, boolean, string, void, any, array, named types, function types, interface field lists
• Class: lowered into constructor/prototype assignments

• ES modules (import/export) - parsed but not fully executed
• with statement (deprecated)
• Private fields (#field)

#Interpreter Scope

• Control flow: if, while, for, for-of (arrays/strings/iterables), break/continue, return, throw, try/catch/finally, switch
• Functions: declarations, expressions, arrows, closures, generators, async functions, async generators
• Objects/Arrays: property access, assignment, deletion, spread
• Special: eval (direct), new, super (limited), __proto__

#Built-in Objects

#test262 Compatibility

#Pass Rate by Category (2026-02-01)

#Not Tested / Not Supported

• Intl402 - Internationalization API
• Temporal - Temporal API
• with statement - Deprecated feature
• Dynamic eval - Advanced eval features
• ES Modules - Parser accepts but not executed

#Partial Support

• TypedArray - Int8Array, Uint8Array, Int16Array, Uint16Array, Int32Array, Uint32Array, Float32Array, Float64Array, BigInt64Array, BigUint64Array
• BigInt - Basic operations

#Experimental Wasm Codegen Scope

• Statements: let/const, assignments, if, while, do-while, for, for-of (arrays), switch, break/continue, return, block/expr statements
• Expressions: literals, variables, arithmetic/comparison/bitwise, string +, array access/length, struct field access, new Array(size), new <interface> struct allocation, ternary, nullish coalescing (??)
• experimental wasm-gc: GC arrays, GC structs, generator state machines

• throw, try/catch/finally
• typeof, void, delete
• Object literals, closures (arrow/function expressions)
• Dynamic call expressions

#Package Bridge Scaffolds

#Unified CLI

# MoonBit -> TypeScript. Run `moon info` first so pkg.generated.mbti exists.
# This creates temporary MoonBit glue code, runs `moon build --target js`,
# and emits a TypeScript package backed by the built JS output.
tsmbt --input mizchi/foo --out dist

# TypeScript -> MoonBit. For bare npm-style inputs, the runtime module spec
# defaults to the input specifier.
tsmbt --input neverthrow --out dist --direction ts-to-mbt

# File input also works; pass the runtime module when it differs from the
# declaration entry path.
tsmbt --input path/to/entry.d.ts --module-spec /runtime/module.js --out dist --direction ts-to-mbt

#MoonBit -> TypeScript

• index.js copied from the temporary glue package's moon build --target js output
• package.json with types / exports metadata for the emitted declaration package
• AUTOLINK_DIAGNOSTICS.md listing public methods/constructors omitted from link.js.exports
• recursive .d.ts files with local MoonBit package imports rewritten to sibling relative imports

moon run src -- emit-typescript-scaffold-from-mbti src/pkg.generated.mbti out/ts-pkg

# optional: rewrite external MoonBit package imports to publishable TS specifiers
moon run src -- emit-typescript-scaffold-from-mbti src/pkg.generated.mbti out/ts-pkg import-rewrites.json

# opt-in: also emit top-level MoonBit wrappers for omitted root-local methods/constructors
moon run src -- emit-typescript-facade-scaffold-from-mbti src/pkg.generated.mbti out/ts-pkg

# only link.js.exports JSON
moon run src -- emit-js-link-config-from-mbti src/pkg.generated.mbti

# only recursive .d.ts package
moon run src -- emit-typescript-package-from-mbti src/pkg.generated.mbti out/ts-pkg

# single .d.ts from one .mbti file without recursive rewrite
moon run src -- emit-typescript-from-mbti src/pkg.generated.mbti

• JS autolink is generated from top-level public free functions only.
• Runtime-inaccessible method / namespace declarations are stripped from scaffold .d.ts output unless wrapper glue is generated for them.
• Scaffold output includes AUTOLINK_DIAGNOSTICS.md so omitted public members are explicit.
• emit-typescript-facade-scaffold-from-mbti is an opt-in variant that adds generated top-level wrappers for root-package local non-generic methods and constructors to the temporary glue package, then exposes those wrappers from the built index.js and index.d.ts.
• The temporary moon.pkg.json and wrapper .mbt files are build inputs only; they are not written to the final TypeScript package.
• Recursive .mbti resolution only rewrites imports that stay under the same root package prefix. External imports remain bare specifiers.
• emit-typescript-package-from-mbti and emit-typescript-scaffold-from-mbti accept an optional JSON object for external import rewrites, for example { "moonbitlang/core/debug": "demo-debug" }.
• Generated package.json names are derived from the MoonBit package path, for example demo/pkg -> @demo/pkg and mizchi/ts/analysis -> @mizchi/ts-analysis.

#TypeScript -> MoonBit

moon run src -- emit-moonbit-scaffold-from-ts path/to/entry.d.ts /runtime/module.js out/moonbit-pkg

# full bridge package
moon run src -- emit-moonbit-bridge-package path/to/entry.d.ts /runtime/module.js out/moonbit-pkg

# inspect generated decl/ffi/bridge snippets without writing a package
moon run src -- emit-moonbit-bridge path/to/entry.d.ts /runtime/module.js
moon run src -- emit-moonbit-js-ffi path/to/entry.d.ts /runtime/module.js
moon run src -- emit-moonbit-decl path/to/entry.d.ts

• Namespace exports are emitted as opaque getter-style bindings such as get_shapes() -> Shapes.
• Ambiguous re-exports no longer block scaffold generation. They are widened/omitted the same way as the lower-level emitters, and the scaffold writes SCAFFOLD_DIAGNOSTICS.md so the dropped surface is explicit.
• Generated bridge packages preserve camelCase top-level export names in their public MoonBit API, even when the internal JS extern binding is lowered to snake_case.

#Development

# Check for errors
moon check --deny-warn

# Run tests
moon test --target native

# Verify high-level scaffold commands end-to-end
just verify-scaffolds

# Format code
moon fmt

# Run test262 (requires test262 repo in ./test262)
moon run src -- test262 test262.allowlist.txt

# Experimental AOT compilation (wasm-gc)
just experimental-aot-check      # Check AOT compilability
just experimental-aot-compile    # Compile fixtures to wasm
just experimental-aot-test       # Run with wasmtime

#License