Re: A question about cp/pt.c:type_unification_real

[Nathan Sidwell <nathan at codesourcery dot com>]

Kazu Hirata wrote:
> Hi,
>
> I have a question about cp/pt.c:type_unification_real.

> However, "args" appears to be a parameter list, too.  For example,
> type_unification_real contains code like:

> Even more confusing is:
>
>       arg = TREE_VALUE (args);
>       :
>       :
> 	  if (!TYPE_P (arg))
>
> Can a function argument be a type?

type_unification_real is used for three things,

* For function call deduction-like things.  ARGS will be a list of expressions 
for a function call (this will affected by Sandra's changes).

* For partial specialization ordering.  ARGS will be a function parameter list.

* for type unification. ARGS will be a function type's arg types. (this is the 
call from 'unify'.)

As you can see all these uses currently represent those distinct types as a 
TREE_LIST.  Sandra will change the first one to a CALL_EXPR.  The second and 
third will be changed by your modifications.

In the first two of these cases, it is called from type_unification.  You'll see 
that that can push the return type onto the start of arg & parms lists, so even 
there an element of ARGS can be a type.

It may be that type_unification_real needs cloning into two variants for the 
distinct type of ARGS.  the pushing of the return type certainly needs 
separating out (as a distinct argument probably).

nathan

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