On Monday, 27 August 2012 at 13:44:43 UTC, Manu wrote:
On 27 August 2012 15:48, Robert Clipsham
<[email protected]> wrote:
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.
Cached in a hashmap! precisely what I suspected (without
knowing anything
about it) ;)
That explains why Walter keeps going on about the name
mangling. It's all
clear.
This discussion is all sorts of wrong. Whoever said that defargs
are metadata (Manu?) was right. Therefore it would make sense to
implement a general metadata facility for D and use *that* for
defargs. C++11 has annotations, so that's the place to start
looking at. D has already enough of those pesky special case
features, let's not add yet another one at the expense of a more
general metadata/annotation mechanism which eventually would be
added anyway due to popular demand.
