Can getHash be made pure?

[H. S. Teoh]

On Fri, Mar 09, 2012 at 02:01:01PM -0800, Walter Bright wrote:
> On 3/9/2012 1:54 PM, H. S. Teoh wrote:
> >Still chugging away at implementing AA's in druntime proper, I reviewed
> >the code for methods that can be marked pure but ran into a major road
> >block: getHash() is not marked pure. That makes a lot of AA methods
> >impure, that could, and probably should, be marked pure.
> >
> >Is it possible to make TypeInfo.getHash() pure? AFAICT there's no good
> >reason why it shouldn't be pure. Am I missing something?
> 
> It should be const, pure, nothrow, @safe.

Hmph.

I tried to make getHash() const pure nothrow @safe, but found that in
some places it calls toHash() which isn't marked const pure nothrow
@safe.  So I fixed that as well, then found that toHash() calls
toString() which isn't pure, nothrow, nor @safe... and before I knew it,
I was deep into marking a *lot* of druntime functions (as perhaps they
*should* be), and then I ran into this:

src/object_.d(648): Error: function object.TypeInfo_AssociativeArray.next () is not callable using argument types ()
src/object_.d(648): Error: function object.TypeInfo_AssociativeArray.next () is not callable using argument types ()
src/object_.d(759): Error: function object.TypeInfo_Class.info () is not callable using argument types ()
src/object_.d(1334): Error: cannot uniquely infer foreach argument types
src/core/runtime.d(483): Error: cannot uniquely infer foreach argument types
make: *** [lib/libdruntime-linux32.a] Error 1

I'm not sure how to proceed from here.

A related question though: have we implemented automatic propagation of
attributes like pure/nothrow/etc., yet? Just wondering if I can just
modify the base class and have the attributes propagate, or I have to
search for every override of every affected function in order to mark
them (as I have been doing -- just wanted to make sure it isn't for
nothing).


T

-- 
It won't be covered in the book. The source code has to be useful for
something, after all. -- Larry Wall