[New] add types

.attw.json

@@ -0,0 +1,5 @@
+{
+	"ignoreRules": [
+		"named-exports"
+	]
+}

.editorconfig

@@ -0,0 +1,20 @@
+root = true
+
+[*]
+indent_style = tab
+indent_size = 4
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+max_line_length = 150
+
+[CHANGELOG.md]
+indent_style = space
+indent_size = 2
+
+[*.json]
+max_line_length = off
+
+[Makefile]
+max_line_length = off

index.d.ts

@@ -0,0 +1,12 @@
+declare namespace SLOT {
+	type InternalSlot = string; // `[[${string}]]`; // TODO: restrict this to require the brackets
+}
+
+declare const SLOT: {
+	assert(O: object, slot: SLOT.InternalSlot): void;
+	get(O: object, slot: SLOT.InternalSlot): unknown;
+	set(O: object, slot: SLOT.InternalSlot, value?: unknown): void;
+	has(O: object, slot: SLOT.InternalSlot): boolean;
+}
+
+export = SLOT;

index.js

@@ -1,10 +1,15 @@
 'use strict';
 
+/** @typedef {`$${import('.').InternalSlot}`} SaltedInternalSlot */
+/** @typedef {{ [k in SaltedInternalSlot]?: unknown }} SlotsObject */
+
 var hasOwn = require('hasown');
+/** @type {import('side-channel').Channel<object, SlotsObject>} */
 var channel = require('side-channel')();
 
 var $TypeError = require('es-errors/type');
 
+/** @type {import('.')} */
 var SLOT = {
 	assert: function (O, slot) {
 		if (!O || (typeof O !== 'object' && typeof O !== 'function')) {
@@ -26,7 +31,8 @@ var SLOT = {
 			throw new $TypeError('`slot` must be a string');
 		}
 		var slots = channel.get(O);
-		return slots && slots['$' + slot];
+		// eslint-disable-next-line no-extra-parens
+		return slots && slots[/** @type {SaltedInternalSlot} */ ('$' + slot)];
 	},
 	has: function (O, slot) {
 		if (!O || (typeof O !== 'object' && typeof O !== 'function')) {
@@ -36,7 +42,8 @@ var SLOT = {
 			throw new $TypeError('`slot` must be a string');
 		}
 		var slots = channel.get(O);
-		return !!slots && hasOwn(slots, '$' + slot);
+		// eslint-disable-next-line no-extra-parens
+		return !!slots && hasOwn(slots, /** @type {SaltedInternalSlot} */ ('$' + slot));
 	},
 	set: function (O, slot, V) {
 		if (!O || (typeof O !== 'object' && typeof O !== 'function')) {
@@ -50,7 +57,8 @@ var SLOT = {
 			slots = {};
 			channel.set(O, slots);
 		}
-		slots['$' + slot] = V;
+		// eslint-disable-next-line no-extra-parens
+		slots[/** @type {SaltedInternalSlot} */ ('$' + slot)] = V;
 	}
 };
 

package.json

@@ -10,7 +10,8 @@
 		"version": "auto-changelog && git add CHANGELOG.md",
 		"postversion": "auto-changelog && git add CHANGELOG.md && git commit --no-edit --amend && git tag -f \"v$(node -e \"console.log(require('./package.json').version)\")\"",
 		"pretest": "npm run lint",
-		"lint": "eslint .",
+		"lint": "eslint --ext=js,mjs .",
+		"postlint": "tsc && attw -P",
 		"tests-only": "nyc tape 'test/**/*.js'",
 		"test": "npm run tests-only",
 		"posttest": "npx npm@'>= 10.2' audit --production"
@@ -41,7 +42,12 @@
 		"node": ">= 0.4"
 	},
 	"devDependencies": {
+		"@arethetypeswrong/cli": "^0.17.1",
 		"@ljharb/eslint-config": "^21.1.1",
+		"@ljharb/tsconfig": "^0.2.2",
+		"@types/for-each": "^0.3.3",
+		"@types/object-inspect": "^1.13.0",
+		"@types/tape": "^5.6.5",
 		"auto-changelog": "^2.5.0",
 		"encoding": "^0.1.13",
 		"eslint": "=8.8.0",
@@ -51,7 +57,8 @@
 		"nyc": "^10.3.2",
 		"object-inspect": "^1.13.3",
 		"safe-publish-latest": "^2.0.0",
-		"tape": "^5.9.0"
+		"tape": "^5.9.0",
+		"typescript": "next"
 	},
 	"dependencies": {
 		"es-errors": "^1.3.0",

test/index.js

@@ -9,6 +9,7 @@ var SLOT = require('../');
 test('assert', function (t) {
 	forEach([null, undefined, true, false, 'foo', '', 42, 0], function (primitive) {
 		t['throws'](
+			// @ts-expect-error
 			function () { SLOT.assert(primitive, ''); },
 			TypeError,
 			inspect(primitive) + ' is not an Object'
@@ -17,14 +18,15 @@ test('assert', function (t) {
 
 	forEach([null, undefined, true, false, 42, 0, {}, [], function () {}, /a/g], function (nonString) {
 		t['throws'](
+			// @ts-expect-error
 			function () { SLOT.assert({}, nonString); },
 			TypeError,
 			inspect(nonString) + ' is not a String'
 		);
 	});
 
 	t['throws'](
-		function () { SLOT.assert({}, 'whatever'); },
+		function () { SLOT.assert({}, '[[whatever]]'); },
 		TypeError,
 		'nonexistent slot throws'
 	);
@@ -40,6 +42,7 @@ test('assert', function (t) {
 test('has', function (t) {
 	forEach([null, undefined, true, false, 'foo', '', 42, 0], function (primitive) {
 		t['throws'](
+			// @ts-expect-error
 			function () { SLOT.has(primitive, ''); },
 			TypeError,
 			inspect(primitive) + ' is not an Object'
@@ -48,6 +51,7 @@ test('has', function (t) {
 
 	forEach([null, undefined, true, false, 42, 0, {}, [], function () {}, /a/g], function (nonString) {
 		t['throws'](
+			// @ts-expect-error
 			function () { SLOT.has({}, nonString); },
 			TypeError,
 			inspect(nonString) + ' is not a String'
@@ -56,7 +60,7 @@ test('has', function (t) {
 
 	var o = {};
 
-	t.equal(SLOT.has(o, 'nonexistent'), false, 'nonexistent slot yields false');
+	t.equal(SLOT.has(o, '[[nonexistent]]'), false, 'nonexistent slot yields false');
 
 	SLOT.set(o, 'foo');
 	t.equal(SLOT.has(o, 'foo'), true, 'existent slot yields true');
@@ -67,6 +71,7 @@ test('has', function (t) {
 test('get', function (t) {
 	forEach([null, undefined, true, false, 'foo', '', 42, 0], function (primitive) {
 		t['throws'](
+			// @ts-expect-error
 			function () { SLOT.get(primitive, ''); },
 			TypeError,
 			inspect(primitive) + ' is not an Object'
@@ -75,6 +80,7 @@ test('get', function (t) {
 
 	forEach([null, undefined, true, false, 42, 0, {}, [], function () {}, /a/g], function (nonString) {
 		t['throws'](
+			// @ts-expect-error
 			function () { SLOT.get({}, nonString); },
 			TypeError,
 			inspect(nonString) + ' is not a String'
@@ -94,6 +100,7 @@ test('get', function (t) {
 test('set', function (t) {
 	forEach([null, undefined, true, false, 'foo', '', 42, 0], function (primitive) {
 		t['throws'](
+			// @ts-expect-error
 			function () { SLOT.set(primitive, ''); },
 			TypeError,
 			inspect(primitive) + ' is not an Object'
@@ -102,6 +109,7 @@ test('set', function (t) {
 
 	forEach([null, undefined, true, false, 42, 0, {}, [], function () {}, /a/g], function (nonString) {
 		t['throws'](
+			// @ts-expect-error
 			function () { SLOT.set({}, nonString); },
 			TypeError,
 			inspect(nonString) + ' is not a String'

tsconfig.json

@@ -0,0 +1,9 @@
+{
+	"extends": "@ljharb/tsconfig",
+	"compilerOptions": {
+		//"target": "es2021",
+	},
+	"exclude": [
+		"coverage",
+	],
+}