Run TypeScript on the types (#1042)

Co-authored-by: ehmicky <[email protected]>

Author: sindresorhus

package.json

@@ -20,7 +20,7 @@
 		"node": ">=18"
 	},
 	"scripts": {
-		"test": "xo && c8 ava && tsd"
+		"test": "xo && c8 ava && tsd && tsc"
 	},
 	"files": [
 		"index.js",
@@ -72,6 +72,7 @@
 		"path-key": "^4.0.0",
 		"tempfile": "^5.0.0",
 		"tsd": "^0.31.0",
+		"typescript": "^5.4.5",
 		"which": "^4.0.0",
 		"xo": "^0.58.0"
 	},

test-d/return/result-main.test-d.ts

@@ -53,7 +53,7 @@ expectType<[]>(unicornsResultSync.pipedFrom);
 
 const error = new Error('.');
 if (error instanceof ExecaError) {
-	expectAssignable<ExecaError>(error);
+	expectType<ExecaError<any>>(error);
 	expectType<'ExecaError'>(error.name);
 	expectType<string>(error.message);
 	expectType<number | undefined>(error.exitCode);
@@ -75,7 +75,7 @@ if (error instanceof ExecaError) {
 
 const errorSync = new Error('.');
 if (errorSync instanceof ExecaSyncError) {
-	expectAssignable<ExecaSyncError>(errorSync);
+	expectType<ExecaSyncError<any>>(errorSync);
 	expectType<'ExecaSyncError'>(errorSync.name);
 	expectType<string>(errorSync.message);
 	expectType<number | undefined>(errorSync.exitCode);

tsconfig.json

@@ -0,0 +1,11 @@
+{
+	"compilerOptions": {
+		"module": "nodenext",
+		"moduleResolution": "nodenext",
+		"target": "ES2022",
+		"strict": true
+	},
+	"files": [
+		"index.d.ts"
+	]
+}