[Issue 7432] DMD allows variables to be declared as pure

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http://d.puremagic.com/issues/show_bug.cgi?id=7432



--- Comment #11 from Jonathan M Davis <jmdavisProg at gmx.com> 2013-08-18 14:14:17 PDT ---
> In the absence of any explanation of what pure means applied to variables, I
> can only be assumed that pure cannot be applied to variables, and therefore 
> any attempt to apply pure to a variable is supposed to fail with a compile 
> error.

Except that in most cases, an invalid attribute doesn't result in a compilation
error - it's ignored. The argument for this is generally that it helps generic
code, and it makes it easier to do stuff like

attribute:
...

or

attribute
{
}

without caring about the items that it doesn't apply to. For instance, you can
do that with attributes like @safe or @trusted, which have zero effect on
variables and yet have lots of variables declared in that code. The same goes
for pure.

I don't know what the best way to handle this is given that sometimes it is
useful to have an attribute ignored when it doesn't apply, but it also can be
quite misleading, and the case where a symbol is explicitly marked with an
attribute and then that attribute is ignored is particularly bad. Maybe we
could petition for that particular case to always be an error (which would
cover this bug), but I don't see it changing for attribute: or attribute {}. I
don't see a good argument for

pure foo = "hello";

being legal though unless the argument is that all invalid attributes are
ignored (which is not the case).

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