tests/cases/conformance/es6/variableDeclarations/VariableDeclaration8_es6.ts(1,1): error TS1153: 'let' declarations are only available when targeting ECMAScript 6 and higher. ==== tests/cases/conformance/es6/variableDeclarations/VariableDeclaration8_es6.ts (1 errors) ==== let a = 1 ~~~ !!! error TS1153: 'let' declarations are only available when targeting ECMAScript 6 and higher.