[dmd-beta] D2 2.058 beta

Martin Nowak dawg at dawgfoto.de
Sat Feb 11 02:57:13 PST 2012

// I.
void foo(V)(in V v)

// II.
void foo(Args...)(auto ref const Args args)

void main()


Deducing foo(10)
function arguments: rvalue int
I.  - MATCHconst
II. - MATCHexact

picks II


Deducing foo(args[0])
function arguments: lvalue const(int)
I.  - MATCHexact
II. - MATCHexact

This is further disambiguated by leastAsSpecialized.
         /* A non-variadic template is more specialized than a
          * variadic one.
         if (isVariadic() && !td2->isVariadic())

picks I


We end up instantiating both functions with the same argument types.
Thus the mangling is the same and the linker will pick whatever he likes.

1. I think that variadic templates shouldn't be exact matches.
2. We shouldn't use tiebreakers but issue ambiguous errors.

A quick fix would be to change variadic templates to MATCHconvert as in  
the attached patch.
But I think we should reduce the complexity of template matching rather  
than patching it.
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