Possible bug in overload resolution

[bluescarni]

I am running in a compilation failure on 32bit platforms for the shortest-paths.cxx test. The symptoms are the following:

/home/bluescarni/repos/graph/include/andres/graph/shortest-paths.hxx:1542:22: error: lvalue required as left operand of assignment
         distances[v] = infinity;
         ~~~~~~~~~~~~~^~~~~~~~~~
/home/bluescarni/repos/graph/include/andres/graph/shortest-paths.hxx:1547:19: error: lvalue required as left operand of assignment
     distances[vs] = 0;
     ~~~~~~~~~~~~~~^~~
/home/bluescarni/repos/graph/include/andres/graph/shortest-paths.hxx:1565:45: error: lvalue required as left operand of assignment
                     distances[it->vertex()] = alternativeDistance;
                     ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~

The problem seems to be that, on some 32bit platforms, std::size_t and unsigned are the same type. What happens then is that this call:

https://github.com/bjoern-andres/graph/blob/master/include/andres/graph/shortest-paths.hxx#L1364

resolves to this function (on 32bit platforms)

https://github.com/bjoern-andres/graph/blob/master/include/andres/graph/shortest-paths.hxx#L1376

rather than this:

https://github.com/bjoern-andres/graph/blob/master/include/andres/graph/shortest-paths.hxx#L1448

So when the flow finally gets inside this function:

https://github.com/bjoern-andres/graph/blob/master/include/andres/graph/shortest-paths.hxx#L1516

DISTANCE_ITERATOR is of type UnitEdgeValueIterator, and the line distances[v] = infinity; fails because distances[v] yields a value rather than a reference.

The issue can be reproduced on 32bit build on MSVC, clang and gcc.