Summary

bun-types@1.3.12 fails under tsgo / TypeScript native preview because bun:ffi declares duplicate computed keys in FFITypeToArgsType and FFITypeToReturnsType.

The problem reproduces with a clean minimal project outside our repo.

Versions

• bun-types: 1.3.12
• typescript: 6.0.2
• @typescript/native-preview: 7.0.0-dev.20260326.1
• @effect/tsgo: 0.2.1

Minimal repro

package.json

{
  "private": true,
  "type": "module",
  "devDependencies": {
    "@effect/tsgo": "0.2.1",
    "@typescript/native-preview": "7.0.0-dev.20260326.1",
    "bun-types": "1.3.12",
    "typescript": "6.0.2"
  }
}

tsconfig.json

{
  "compilerOptions": {
    "noEmit": true,
    "strict": true,
    "types": ["bun-types"]
  },
  "include": ["index.ts"]
}

index.ts

export {};

Commands:

pnpm install
pnpm exec tsgo --noEmit -p tsconfig.json

Actual result

The compile fails with duplicate identifier errors from bun-types/ffi.d.ts, for example:

node_modules/.pnpm/bun-types@1.3.12/node_modules/bun-types/ffi.d.ts(347,5): error TS2300: Duplicate identifier '[FFIType.int8_t]'.
node_modules/.pnpm/bun-types@1.3.12/node_modules/bun-types/ffi.d.ts(349,5): error TS2300: Duplicate identifier '[FFIType.uint8_t]'.
node_modules/.pnpm/bun-types@1.3.12/node_modules/bun-types/ffi.d.ts(355,5): error TS2300: Duplicate identifier '[FFIType.int32_t]'.
node_modules/.pnpm/bun-types@1.3.12/node_modules/bun-types/ffi.d.ts(364,5): error TS2300: Duplicate identifier '[FFIType.double]'.
node_modules/.pnpm/bun-types@1.3.12/node_modules/bun-types/ffi.d.ts(369,5): error TS2300: Duplicate identifier '[FFIType.ptr]'.

Why this seems wrong

The published declarations include both canonical enum members and legacy aliases as separate computed keys:

[FFIType.int8_t]: number;
[FFIType.i8]: number;
...
[FFIType.ptr]: Pointer | null;
[FFIType.pointer]: Pointer | null;

When those enum values collapse to the same computed property key, tsgo reports them as duplicates.

The same pattern exists in both:

• FFITypeToArgsType
• FFITypeToReturnsType

Relevant published declarations

From the published tarball for bun-types@1.3.12:

• ffi.d.ts contains the duplicate alias pairs
• wasm.d.ts also contains:

interface ModuleExportDescriptor extends Bun.WebAssembly.ModuleExportDescriptor {}
interface ModuleImportDescriptor extends Bun.WebAssembly.ModuleImportDescriptor {}

We locally patched both areas, but the ffi.d.ts duplicate keys are the directly reproducible failure above.

Expected result

bun-types should typecheck cleanly under the current TypeScript native preview / tsgo toolchain without requiring a local patch that removes the alias duplicates.