On Oct 29, 2014, at 4:13 PM, C. Scott Ananian <[email protected]> wrote:
> Don't forget the implications for the future. If declaring certain > names in top level scopes is an error if they are also present in the > global or host environment, it means that ES7+ can never define new > names on the global (or HTML6+ can never define new names in the host > environment) without risking hard errors in existing code. > --scott A good point, even though we are only talking about let/const/class declarations. We couldn’t want the possibility that some body has a global let declaration for ‘Foo’ to prevent us (or a host such as the browser) from ever defining a new built-in global named ‘Foo’. (although, I suspect there is an argument to be made that because we now have modules that all future global candidates should instead be exports from built-in modules). This brings me around to the position that let-like global instantiation should reject let-shadowing of non-configurable property global properties such as ‘undefined’ and ‘window’. The VarNames list is actually support a different case. The general case is that we down’t allow the same name to be explicitly declared using both a ‘var’ and a ‘let’ (etc.) declaration in any scope, including the global scope. However, we only apply that rule to explicit global var/function declarations. Undeclared global properties are “in the global scope” but are not considered to be var declarations. Allen _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
