text: // Copyright 2013 the V8 project authors. All rights reserved.
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  //       notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  //       copyright notice, this list of conditions and the following
  //       disclaimer in the documentation and/or other materials provided
  //       with the distribution.
  //     * Neither the name of Google Inc. nor the names of its
  //       contributors may be used to endorse or promote products derived
  //       from this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  // Flags: --harmony-generators
  
  // Test basic generator syntax.
  
  // Yield statements.
  function* g() { yield 3; yield 4; }
  
  // Yield expressions.
  function* g() { (yield 3) + (yield 4); }
  
  // You can have a generator in strict mode.
  function* g() { "use strict"; yield 3; yield 4; }
  
  // Generators can have return statements also, which internally parse to a kind
  // of yield expression.
  function* g() { yield 1; return; }
  function* g() { yield 1; return 2; }
  function* g() { yield 1; return 2; yield "dead"; }
  
  // Generator expression.
  (function* () { yield 3; });
  
  // Named generator expression.
  (function* g() { yield 3; });
  
  // A generator without a yield is specified as causing an early error.  This
  // behavior is currently unimplemented.  See
  // https://bugs.ecmascript.org/show_bug.cgi?id=1283.
  function* g() { }
  
  // A YieldExpression in the RHS of a YieldExpression is currently specified as
  // causing an early error.  This behavior is currently unimplemented.  See
  // https://bugs.ecmascript.org/show_bug.cgi?id=1283.
  function* g() { yield yield 1; }
  function* g() { yield 3 + (yield 4); }
  
  // Generator definitions with a name of "yield" are not specifically ruled out
  // by the spec, as the `yield' name is outside the generator itself.  However,
  // in strict-mode, "yield" is an invalid identifier.
  function* yield() { (yield 3) + (yield 4); }
  assertThrows("function* yield() { \"use strict\"; (yield 3) + (yield 4); }",
               SyntaxError);
  
  // In sloppy mode, yield is a normal identifier, outside of generators.
  function yield(yield) { yield: yield (yield + yield (0)); }
  
  // Yield is always valid as a key in an object literal.
  ({ yield: 1 });
  function* g() { yield ({ yield: 1 }) }
  function* g() { yield ({ get yield() { return 1; }}) }
  
  // Checks that yield is a valid label in sloppy mode, but not valid in a strict
  // mode or in generators.
  function f() { yield: 1 }
  assertThrows("function f() { \"use strict\"; yield: 1 }", SyntaxError)
  assertThrows("function* g() { yield: 1 }", SyntaxError)
  
  // Yield is only a keyword in the body of the generator, not in nested
  // functions.
  function* g() { function f() { yield (yield + yield (0)); } }
  
  // Yield needs a RHS.
  assertThrows("function* g() { yield; }", SyntaxError);
  
  // Yield in a generator is not an identifier.
  assertThrows("function* g() { yield = 10; }", SyntaxError);
  
  // Yield binds very loosely, so this parses as "yield (3 + yield 4)", which is
  // invalid.
  assertThrows("function* g() { yield 3 + yield 4; }", SyntaxError);
  
  // Yield is still a future-reserved-word in strict mode
  assertThrows("function f() { \"use strict\"; var yield = 13; }", SyntaxError);
  
  // The name of the NFE is let-bound in G, so is invalid.
  assertThrows("function* g() { yield (function yield() {}); }", SyntaxError);
  
  // In generators, yield is invalid as a formal argument name.
  assertThrows("function* g(yield) { yield (10); }", SyntaxError);
  