The Tor Browser / file revision

 // Check that we correctly throw SyntaxErrors for various syntactic near-misses.

 load(libdir + "asserts.js");

 var mistakes = [

     "((a)) => expr",

     "a + b => a",

     "'' + a => a",

     "...x",

     "[x] => x",

     "([x] => x)",

     "{p: p} => p",

     "({p: p} => p)",

     "{p} => p",

     "(...x => expr)",

     "1 || a => a",

     "'use strict' => {}",

     "package => {'use strict';}",    // tricky: FutureReservedWord in strict mode code only

     "'use strict'; arguments => 0",  // names banned in strict mode code

     "'use strict'; eval => 0",

     "a => {'use strict'; with (a) return x; }",

     "a => yield a",

     "a => { yield a; }",

     "a => { { let x; yield a; } }",

     "(a = yield 0) => a",

     "for (;;) a => { break; };",

     "for (;;) a => { continue; };",

     "...rest) =>",

     "2 + ...rest) =>"

 ];

 for (var s of mistakes)

     assertThrowsInstanceOf(function () { Function(s); }, SyntaxError);

 // Check that the tricky case is not an error in non-strict-mode code.

 var f = package => 0;

 assertEq(f(1), 0);