Commits on Aug 8, 2016

1. Removed problematic templated overloads on callback-based functions …

   Before this commit, the following pattern was suggested as a shortcut
   for writing callback-based functions overloaded based on arguments:
   
       template <typename T, typename M>
       void attach(T *obj, M method) {
           attach(Callback<void()>(obj, method);
       }
   
   Unfortunately, C++ did not fair well with this level of type-inference.
   
   The initial problems were with variable-arity function. The M type would
   happily consume arguments during overload-resolution, only to fail during
   template-expansion. Removed from problematic functions, this bug was
   unfortunately easy to reintroduce (for example in the RtosTimer) since
   it is undectable without forcing the template to expand.
   
   The latest problem is occuring during type-deduction of overloaded
   function pointers. The extra level of indirection with the templated-
   method parameter caused type-deduction to stop early, erroring with
   an ambiguity error. Even more unfortunate, this error is inconsistent,
   since some functions were unable to adopt the template-method pattern
   for the variable-arity issue mentioned earlier.
   
   For example:
   
       class Thing {
           void doit(int timeout);
           void doit();
       };
   
       Thing t;
   
       serial.attach(&t, &Thing::doit); // perfectly fine
       timer.attach(&t, &Thing::doit);  // ambiguity compile error
   
   After running into these issues with this design pattern, the best path
   forward seems to be to simply remove the templated-method overloads.
   These have been replaced by the two explicit overloads for the existing
   callback arguments.

   

   geky committed Aug 8, 2016
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