Function pointers/delegates default args were stealth removed?

[Timon Gehr]

On 08/27/2012 02:48 PM, Robert Clipsham wrote:
> On Monday, 27 August 2012 at 10:32:28 UTC, Manu wrote:
>>> Because the two types were considered to be the same, only different.
>>
>> And how was that a problem? They never interacted in the example, the
>> assignments were totally separate, they shouldn't have been confused.
>> Just speculating, but it just looks like the type was misrepresented when
>> it was looked up from a map by name or something, and matched the wrong
>> cached definition... or something along those lines.
>> It looks like a bug exposed from implementation detail, I can't see
>> anything in the bug report that shouldn't theoretically work fine.
>
> I seem to recall I looked at this issue myself at one point. It goes
> something like:
> ----
> auto foo = (int a = 1) { return a; };
> auto bar = (int a) { return a; };
> ----
> int function(int) is mangled exactly the same as int function(int = 1)
> as default args aren't used for mangling. dmd does semantic analysis on
> the type of foo, which returns int function(int = 1), which is mangled
> as int function(int) and stored in dmd's hashmap of types (default args
> aren't mangled). When the semantic analysis of bar is done it checks the
> hashmap, sees that the type is already there (has the same name
> mangling) and does not repeat semantic analysis. If you switch the order
> of declarations then the opposite happens - the default arg is ignored.

If the compiler design *requires* equal types to be stored uniquely in
a hash map, then the default args shouldn't be stored as part of the
type in the AST. I assume it is rather inconvenient to fix, but
certainly possible.