tests/cases/conformance/statements/for-ofStatements/ES3For-ofTypeCheck4.ts(2,17): error TS2494: Using a string in a 'for...of' statement is only supported in ECMAScript 5 and higher. ==== tests/cases/conformance/statements/for-ofStatements/ES3For-ofTypeCheck4.ts (1 errors) ==== var union: string | string[]; for (const v of union) { } ~~~~~ !!! error TS2494: Using a string in a 'for...of' statement is only supported in ECMAScript 5 and higher.