[Python-Dev] Re: [Patches] [Patch #101175] Fix slight bug in the Ref manual docs on listcomprehensions

[Tim Peters]

[Tim]
> [x if 6] should not be a legal expression but the grammar
> allows it today.

[Greg Ewing]
> Why shouldn't it be legal?

Because Guido hates it.  It's almost certainly an error on the part of the
user; really the same reason that zip() without arguments raises an
exception.

> ...
> Excluding it will make both the implementation and documentation
> more complicated,

Of course, but marginally so.  "The first clause must be an iterator"; end
of doc changes.

> with no benefit that I can see.

Catching likely errors is a benefit for the user.  I realize that Haskell
does allow it -- although that would be a surprise to most Haskell users
<wink>.