v8/test/mjsunit/regress/regress-4908.js

// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// Flags: --always-opt --no-lazy

(function() { ((s = 17, y = s) => s)() })();
More accurately record an end position for default parameters in arrows Our previous over-conservative answer caused us to emit hole checks in full-codegen when eagerly parsing but not when lazily parsing. With this patch, we use the positions of the BinaryOperations making up the parameter list (which are the positions of the commas) to determine the appropriate "end position" for each parameter's initializer. This means that we get accurate-enough positions for the initializers in the eager parsing step to get the same answers for hole-check-elimination that we will later during ParseLazy. In the included test case, for example: (function() { ((s = 17, y = s) => s)(); } )(); ^2 ^1 The old code would generate a hole check when trying to load \|s\| for assignment to \|y\| (because it treated the closing parentheses pointed to by "^1" as the "initialization position" of \|s\|). The new code uses the comma pointed to by "^2" as the initialization position of \|s\|. Since that occurs textually before the load of \|s\|, full-codegen knows it can avoid the hole check. BUG=v8:4908 LOG=n Review URL: https://codereview.chromium.org/1900343002 Cr-Commit-Position: refs/heads/master@{#35678} 2016-04-20 20:48:32 +00:00			`// Copyright 2016 the V8 project authors. All rights reserved.`
			`// Use of this source code is governed by a BSD-style license that can be`
			`// found in the LICENSE file.`
			`//`
			`// Flags: --always-opt --no-lazy`

			`(function() { ((s = 17, y = s) => s)() })();`