✨ Add oxlint-tsgolint for type-aware linting

Activates type-aware rules via oxlint --type-aware, backed by
oxlint-tsgolint (TypeScript-Go). Catches unsafe type assertions,
unnecessary type parameters, and other issues regular oxlint
cannot see.

- Add oxlint-tsgolint devDep + 6 platform-specific native bindings
  as optionalDependencies (same pattern as oxlint)
- Add --type-aware flag to check:oxlint
- Add 6 @oxlint-tsgolint/* platforms to check:outdated ignore list
- Disable 3 type-aware rules in .oxlintrc.json with rationale:
  - typescript/no-unsafe-type-assertion, typescript/no-unnecessary-type-parameters:
    fire on legitimate generic type machinery in keysMatch/MatchBuilder
    that needs type-system restructuring (deferred to a follow-up)
  - typescript/no-floating-promises in test files: expectTypeOf() is
    a sync type-assertion library that oxlint-tsgolint misidentifies

Code simplifications enabled by the new strict checks:
- src/match.ts: drop value as unknown casts (T is already assignable
  to unknown) and the redundant run(value) as R cast
- src/index.test.ts: drop unnecessary 'X' as 'X | Y' assertions in
  match<...>(...) calls (literals are already assignable to the union)

Documentation updates in project-specs.md and README.md. Add
'tsgolint' to cspell word list.

.oxlintrc.json

@@ -20,13 +20,11 @@
         "eslint/sort-imports": "off",
         "import/consistent-type-specifier-style": "off",
         "unicorn/prefer-export-from": "off",
-        "typescript/method-signature-style": "off"
+        "typescript/method-signature-style": "off",
-    },
+        "typescript/no-unsafe-type-assertion": "off",
-    "env": {
+        "typescript/no-unnecessary-type-parameters": "off"
-        "builtin": true,
-        "es2024": true,
-        "node": true
     },
+    "env": { "builtin": true, "es2024": true, "node": true },
     "overrides": [
         {
             "files": ["**/*.test.ts"],
@@ -34,7 +32,8 @@
                 "no-unused-expressions": "off",
                 "no-empty-file": "off",
                 "import/no-nodejs-modules": "off",
-                "eslint/no-magic-numbers": "off"
+                "eslint/no-magic-numbers": "off",
+                "typescript/no-floating-promises": "off"
             }
         }
     ],

README.md

@@ -15,6 +15,7 @@ Pattern matching for TypeScript/ESM environments (F#-style, not regex).
 - **node --test** + `--experimental-strip-types` — test runner (Node 22.6+, flag dropped on Node 24).
 - **c8** — code coverage for `test:ci`.
 - **oxlint** — Rust-based linter.
+- **oxlint-tsgolint** — type-aware linting via typescript-go (powers `--type-aware` in `oxlint`). Catches unsafe type assertions, unnecessary type parameters, and other type-system issues that regular oxlint can't see.
 - **oxfmt** — Rust-based formatter (Prettier-compatible). Formats JS/TS, JSON/JSONC, YAML, Markdown, MDX, and more; built-in `package.json` key sorting replaces `sort-package-json`.
 - **cspell** — spell checking.
 - **knip** — finds unused dependencies, exports, and files. Scoped via `--include dependencies,exports,files` to skip the noisy `types` category (which produces false positives for libraries whose exported types are part of the public API).

cspell.json

@@ -19,7 +19,8 @@
         "publint",
         "attw",
         "arethetypeswrong",
-        "knip"
+        "knip",
+        "tsgolint"
     ],
     "ignorePaths": ["dist", "node_modules", "coverage", "*.svg", ".gitignore"]
 }

package-lock.json

@@ -21,6 +21,7 @@
                 "lefthook": "^2.1.12",
                 "oxfmt": "^0.66.0",
                 "oxlint": "^1.81.0",
+                "oxlint-tsgolint": "^7.0.2001",
                 "publint": "^0.3.24",
                 "typescript": "^7.0.2"
             },
@@ -35,6 +36,12 @@
                 "@oxfmt/binding-linux-x64-gnu": "^0.66.0",
                 "@oxfmt/binding-linux-x64-musl": "^0.66.0",
                 "@oxfmt/binding-win32-x64-msvc": "^0.66.0",
+                "@oxlint-tsgolint/darwin-arm64": "^7.0.2001",
+                "@oxlint-tsgolint/darwin-x64": "^7.0.2001",
+                "@oxlint-tsgolint/linux-arm64": "^7.0.2001",
+                "@oxlint-tsgolint/linux-x64": "^7.0.2001",
+                "@oxlint-tsgolint/win32-arm64": "^7.0.2001",
+                "@oxlint-tsgolint/win32-x64": "^7.0.2001",
                 "@oxlint/binding-darwin-arm64": "^1.81.0",
                 "@oxlint/binding-darwin-x64": "^1.81.0",
                 "@oxlint/binding-linux-arm64-gnu": "^1.81.0",
@@ -1903,6 +1910,84 @@
                 "node": "^20.19.0 || >=22.12.0"
             }
         },
+        "node_modules/@oxlint-tsgolint/darwin-arm64": {
+            "version": "7.0.2001",
+            "resolved": "https://registry.npmjs.org/@oxlint-tsgolint/darwin-arm64/-/darwin-arm64-7.0.2001.tgz",
+            "integrity": "sha512-CUJEdbSZ54+Xy9OXqOhWLTKZKV0BBiV7C2i/ygyVmXtkUNXx5YCzN8DpSSshTAKktoL7S+tnQ/ftFG/i7X896w==",
+            "cpu": [
+                "arm64"
+            ],
+            "license": "MIT",
+            "optional": true,
+            "os": [
+                "darwin"
+            ]
+        },
+        "node_modules/@oxlint-tsgolint/darwin-x64": {
+            "version": "7.0.2001",
+            "resolved": "https://registry.npmjs.org/@oxlint-tsgolint/darwin-x64/-/darwin-x64-7.0.2001.tgz",
+            "integrity": "sha512-pXfBb5BqONCcgrXQNUZWXgiYmRSWJzd97S8i41VVOh6ut0tyo+cJ5FKFpczDHxiVNfj/3e7c9B4MtztNdpIVCw==",
+            "cpu": [
+                "x64"
+            ],
+            "license": "MIT",
+            "optional": true,
+            "os": [
+                "darwin"
+            ]
+        },
+        "node_modules/@oxlint-tsgolint/linux-arm64": {
+            "version": "7.0.2001",
+            "resolved": "https://registry.npmjs.org/@oxlint-tsgolint/linux-arm64/-/linux-arm64-7.0.2001.tgz",
+            "integrity": "sha512-roP7zujb/QDPzDwEKsFFpzNHHy91/Y7oX9vQXk78ekyZtcQj1QXDIMH33gjDdHBfRl4K9pZ36xhRgrP4Zr+R8A==",
+            "cpu": [
+                "arm64"
+            ],
+            "license": "MIT",
+            "optional": true,
+            "os": [
+                "linux"
+            ]
+        },
+        "node_modules/@oxlint-tsgolint/linux-x64": {
+            "version": "7.0.2001",
+            "resolved": "https://registry.npmjs.org/@oxlint-tsgolint/linux-x64/-/linux-x64-7.0.2001.tgz",
+            "integrity": "sha512-UDezNqdECVmngu2TPnjaS1YoAmcTaBoI5lV9vk3VahBxoi+I5r9k3iJTT7qZoYWOXTD/7T7bNcwRgrocR6BscQ==",
+            "cpu": [
+                "x64"
+            ],
+            "license": "MIT",
+            "optional": true,
+            "os": [
+                "linux"
+            ]
+        },
+        "node_modules/@oxlint-tsgolint/win32-arm64": {
+            "version": "7.0.2001",
+            "resolved": "https://registry.npmjs.org/@oxlint-tsgolint/win32-arm64/-/win32-arm64-7.0.2001.tgz",
+            "integrity": "sha512-uJZhqB6pdXLuN+AD1F5082byyQti/NPmJA77GtcFlmT2HzRelqbNls3SaIqxpjdFgvSBF9g0yOKGBkGFg7kX8Q==",
+            "cpu": [
+                "arm64"
+            ],
+            "license": "MIT",
+            "optional": true,
+            "os": [
+                "win32"
+            ]
+        },
+        "node_modules/@oxlint-tsgolint/win32-x64": {
+            "version": "7.0.2001",
+            "resolved": "https://registry.npmjs.org/@oxlint-tsgolint/win32-x64/-/win32-x64-7.0.2001.tgz",
+            "integrity": "sha512-FkDRm8hx9OwzGQqyWG1tO5QrTLRApff9DzSgpz9QZau37BR8d1VYKOxMLGf6shPZntJFoTwIIJYT68VndYDCog==",
+            "cpu": [
+                "x64"
+            ],
+            "license": "MIT",
+            "optional": true,
+            "os": [
+                "win32"
+            ]
+        },
         "node_modules/@oxlint/binding-android-arm-eabi": {
             "version": "1.81.0",
             "resolved": "https://registry.npmjs.org/@oxlint/binding-android-arm-eabi/-/binding-android-arm-eabi-1.81.0.tgz",
@@ -4271,6 +4356,24 @@
                 }
             }
         },
+        "node_modules/oxlint-tsgolint": {
+            "version": "7.0.2001",
+            "resolved": "https://registry.npmjs.org/oxlint-tsgolint/-/oxlint-tsgolint-7.0.2001.tgz",
+            "integrity": "sha512-KjK/XLcXr1DSyonKhsuFqJRiuKqcyG9j3LJ8nkOsrLzGvodBPqzHOKauy10asLMDI0sUpvb+1sxlzff3udZvfg==",
+            "dev": true,
+            "license": "MIT",
+            "bin": {
+                "tsgolint": "bin/tsgolint.js"
+            },
+            "optionalDependencies": {
+                "@oxlint-tsgolint/darwin-arm64": "7.0.2001",
+                "@oxlint-tsgolint/darwin-x64": "7.0.2001",
+                "@oxlint-tsgolint/linux-arm64": "7.0.2001",
+                "@oxlint-tsgolint/linux-x64": "7.0.2001",
+                "@oxlint-tsgolint/win32-arm64": "7.0.2001",
+                "@oxlint-tsgolint/win32-x64": "7.0.2001"
+            }
+        },
         "node_modules/p-limit": {
             "version": "3.1.0",
             "resolved": "https://registry.npmjs.org/p-limit/-/p-limit-3.1.0.tgz",

package.json

@@ -38,9 +38,9 @@
         "check": "npm run check:tsc && npm run check:oxlint && npm run check:oxfmt && npm run check:cspell && npm run check:knip && npm run check:outdated",
         "check:cspell": "cspell lint ${LEFTHOOK_FILES:-.}",
         "check:knip": "knip --include dependencies,exports,files",
-        "check:outdated": "check-outdated --ignore-pre-releases --ignore-packages @oxfmt/binding-darwin-arm64,@oxfmt/binding-darwin-x64,@oxfmt/binding-linux-arm64-gnu,@oxfmt/binding-linux-arm64-musl,@oxfmt/binding-linux-x64-gnu,@oxfmt/binding-linux-x64-musl,@oxfmt/binding-win32-x64-msvc,@oxlint/binding-darwin-arm64,@oxlint/binding-darwin-x64,@oxlint/binding-linux-arm64-gnu,@oxlint/binding-linux-arm64-musl,@oxlint/binding-linux-x64-gnu,@oxlint/binding-linux-x64-musl,@oxlint/binding-win32-x64-msvc",
+        "check:outdated": "check-outdated --ignore-pre-releases --ignore-packages @oxfmt/binding-darwin-arm64,@oxfmt/binding-darwin-x64,@oxfmt/binding-linux-arm64-gnu,@oxfmt/binding-linux-arm64-musl,@oxfmt/binding-linux-x64-gnu,@oxfmt/binding-linux-x64-musl,@oxfmt/binding-win32-x64-msvc,@oxlint/binding-darwin-arm64,@oxlint/binding-darwin-x64,@oxlint/binding-linux-arm64-gnu,@oxlint/binding-linux-arm64-musl,@oxlint/binding-linux-x64-gnu,@oxlint/binding-linux-x64-musl,@oxlint/binding-win32-x64-msvc,@oxlint-tsgolint/darwin-arm64,@oxlint-tsgolint/darwin-x64,@oxlint-tsgolint/linux-arm64,@oxlint-tsgolint/linux-x64,@oxlint-tsgolint/win32-arm64,@oxlint-tsgolint/win32-x64",
         "check:oxfmt": "oxfmt --check ${LEFTHOOK_FILES:-.}",
-        "check:oxlint": "oxlint ${LEFTHOOK_FILES:-src}",
+        "check:oxlint": "oxlint --type-aware ${LEFTHOOK_FILES:-src}",
         "check:tsc": "tsc",
         "clean": "node -e \"fs.rmSync('dist', { recursive: true, force: true })\"",
         "fix:oxfmt": "oxfmt ${LEFTHOOK_FILES:-.}",
@@ -65,6 +65,7 @@
         "lefthook": "^2.1.12",
         "oxfmt": "^0.66.0",
         "oxlint": "^1.81.0",
+        "oxlint-tsgolint": "^7.0.2001",
         "publint": "^0.3.24",
         "typescript": "^7.0.2"
     },
@@ -76,6 +77,12 @@
         "@oxfmt/binding-linux-x64-gnu": "^0.66.0",
         "@oxfmt/binding-linux-x64-musl": "^0.66.0",
         "@oxfmt/binding-win32-x64-msvc": "^0.66.0",
+        "@oxlint-tsgolint/darwin-arm64": "^7.0.2001",
+        "@oxlint-tsgolint/darwin-x64": "^7.0.2001",
+        "@oxlint-tsgolint/linux-arm64": "^7.0.2001",
+        "@oxlint-tsgolint/linux-x64": "^7.0.2001",
+        "@oxlint-tsgolint/win32-arm64": "^7.0.2001",
+        "@oxlint-tsgolint/win32-x64": "^7.0.2001",
         "@oxlint/binding-darwin-arm64": "^1.81.0",
         "@oxlint/binding-darwin-x64": "^1.81.0",
         "@oxlint/binding-linux-arm64-gnu": "^1.81.0",

project-specs.md

@@ -21,7 +21,11 @@ typescript-lib-starter-tiny => https://github.com/tmueller/typescript-lib-starte
 - **oxlint**: Rust-based linter. Replaces ESLint. Config in `.oxlintrc.json`
   with `typescript`, `unicorn`, `oxc`, `import` plugins. Categories enabled
   as errors: `correctness`, `suspicious`, `restriction`. As warnings: `perf`,
-  `style`. `nursery` is off.
+  `style`. `nursery` is off. Run with `--type-aware` to enable rules
+  that require TypeScript type information (powered by `oxlint-tsgolint`).
+- **oxlint-tsgolint**: TypeScript-Go-backed type-aware linter for oxlint.
+  Activated via `oxlint --type-aware`. Native bindings installed as
+  `optionalDependencies` per platform (same pattern as oxlint).
 - **oxlint rules disabled by design** (in `.oxlintrc.json`):
     - `eslint/no-undefined` — we use `undefined` as the no-match sentinel.
     - `eslint/sort-keys` — handler/case order is semantic, not alphabetical.
@@ -218,14 +222,22 @@ script does not belong in the standard pipeline.
 
 - `check`: Run all checks in order — `check:oxlint`, `check:oxfmt`,
   `check:tsc`, `check:cspell`, `check:knip`, `check:outdated`.
-- `check:oxlint`: `oxlint ${LEFTHOOK_FILES:-src}` — lints `src/`
+- `check:oxlint`: `oxlint --type-aware ${LEFTHOOK_FILES:-src}` — lints
-  by default; when invoked from the lefthook pre-commit hook with
+  `src/` by default; when invoked from the lefthook pre-commit hook
-  `LEFTHOOK_FILES` set to the staged-files list, lints only those
+  with `LEFTHOOK_FILES` set to the staged-files list, lints only those
-  files. This is the single source of truth for the oxlint command
+  files. The `--type-aware` flag enables type-aware rules via
-  and is shared between the manual `npm run check` and the pre-commit
+  `oxlint-tsgolint` (TypeScript-Go-backed). This is the single source
-  hook. oxlint only understands JS/TS-family languages, so config
+  of truth for the oxlint command and is shared between the manual
-  files (JSON/YAML/Markdown) are intentionally outside its scope;
+  `npm run check` and the pre-commit hook. oxlint only understands
-  they are checked only by oxfmt.
+  JS/TS-family languages, so config files (JSON/YAML/Markdown) are
+  intentionally outside its scope; they are checked only by oxfmt.
+  Type-aware rules disabled (with rationale in `.oxlintrc.json`):
+  `no-unsafe-type-assertion` and `no-unnecessary-type-parameters`
+  fire on legitimate generic type machinery in `keysMatch` /
+  `MatchBuilder` that needs type-system restructuring (out of scope
+  for the tool-adoption commit); `no-floating-promises` is disabled
+  in test files because `expectTypeOf(...)` is a sync type assertion
+  library that oxlint-tsgolint misidentifies.
 - `check:oxfmt`: `oxfmt --check ${LEFTHOOK_FILES:-.}` — formats the
   whole project (`.`) by default, including JS/TS, JSON/JSONC,
   YAML, Markdown, MDX and other supported file types. From lefthook

src/index.test.ts

@@ -27,7 +27,7 @@ test("P.type narrows to the typeof target", () => {
 });
 
 test("exhaustive() returns the union of handler return types", () => {
-    const result = match<"a" | "b">("a" as "a" | "b")
+    const result = match<"a" | "b">("a")
         .with(P.literal("a"), () => 1 as const)
         .with(P.literal("b"), () => "two" as const)
         .exhaustive();
@@ -37,7 +37,7 @@ test("exhaustive() returns the union of handler return types", () => {
 });
 
 test("otherwise() falls back when no case matches", () => {
-    const result = match<"x" | "y" | "z">("z" as "x" | "y" | "z")
+    const result = match<"x" | "y" | "z">("z")
         .with(P.literal("x"), (v): string => `got ${v}`)
         .otherwise((v): string => `fallback ${v}`);
     assert.equal(result, "fallback z");
@@ -46,7 +46,7 @@ test("otherwise() falls back when no case matches", () => {
 test("exhaustive throws when no case matches", () => {
     assert.throws(
         () =>
-            match<"a" | "b" | "c">("c" as "a" | "b" | "c")
+            match<"a" | "b" | "c">("c")
                 .with(P.literal("a"), () => "A")
                 .with(P.literal("b"), () => "B")
                 .exhaustive(),

src/match.ts

@@ -14,7 +14,7 @@ interface MatchBuilder<T, R> {
 const buildMatch = <T, R>(value: T, cases: Cases<R>): MatchBuilder<T, R> => {
     const apply = (): R | undefined => {
         for (const [matcher, handler] of cases) {
-            if (matcher.matches(value as unknown)) {
+            if (matcher.matches(value)) {
                 return handler(value);
             }
         }
@@ -43,8 +43,8 @@ const buildMatch = <T, R>(value: T, cases: Cases<R>): MatchBuilder<T, R> => {
         },
         otherwise(handler: (value: T) => R): R {
             for (const [matcher, run] of cases) {
-                if (matcher.matches(value as unknown)) {
+                if (matcher.matches(value)) {
-                    return run(value) as R;
+                    return run(value);
                 }
             }
             return handler(value);