src/third_party/mozjs-45/js/src/jit-test/tests/modules/duplicate-exports.js

// Test errors due to duplicate exports
load(libdir + "asserts.js");

function testSyntaxError(source) {
    assertThrowsInstanceOf(function () {
        parseModule(source);
    }, SyntaxError);
}

testSyntaxError("export var v; export var v;");
testSyntaxError("export var x, y, z; export var y;");
testSyntaxError("export default 1; export default 2;");
testSyntaxError("export var default; export default 1;");
testSyntaxError("export var default; export default function() {};");
testSyntaxError("export var default; export default function foo() {};");
testSyntaxError("var v; export {v}; export {v};");
testSyntaxError("var v, x; export {v}; export {x as v};");
testSyntaxError("export var default; export default export class { constructor() {} };");
testSyntaxError("export var default; export default export class foo { constructor() {} };");