Allow lexically declared "arguments" in function scope in sloppy mode.

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index e978f0b6b4ed311c5c55229dbe4ce41f31b12b88..2fdd9db5b0cf71dd3d504414b96d795dfe39f47e 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -4019,6 +4019,10 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
 
     // Parsing the body may change the language mode in our scope.
     language_mode = scope->language_mode();
+    scope->DeclareArguments(ast_value_factory());
+    if (main_scope != scope) {
+      main_scope->DeclareArguments(ast_value_factory());

[adamk, 2016/08/30 20:45:56]

What happens if you leave this out? I'm a bit surprised it's necessary.

[lpy, 2016/09/01 01:17:30]

There's a DCHECK here:
https://cs.chromium.org/chromium/src/v8/src/ast/scopes.cc?l=1027

+    }
 
     // Validate name and parameter names. We can do this only after parsing the
     // function, since the function can declare itself strict.