Function pointers/delegates default args were stealth removed?

[Robert Clipsham]

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.