Re: Compilation failure involving template operator

The code below surprisingly for me fails compilation on Comeau C++ and
VC++ 9:

----------------------------------------------------------

struct XTestChar
 {
 operator char() const { return c; }
 char c;
 };

template <class T> struct YTestTemplate { };

template <class T>
YTestTemplate<T> &
operator *= (YTestTemplate<T> & first,T second)
 {
 return(first);
 }

XTestChar xtest;
YTestTemplate<char> ytest;

void AFunction()
 {
 ytest *= xtest;
 }

------------------------------------------------------------

Comeau C++ says:

"ComeauTest.c", line 21: error: no operator "*=" matches these operands
           operand types are: YTestTemplate<char> *= XTestChar
   ytest *= xtest;
         ^
1 error detected in the compilation of "ComeauTest.c".

Visual C++ says:

error C2782: 'YTestTemplate<T> &operator *=(YTestTemplate<T> &,T)' :
template parameter 'T' is ambiguous
       see declaration of 'operator *='
       could be 'XTestChar'
       or 'char'
error C2676: binary '*=' : 'YTestTemplate<T>' does not define this
operator or a conversion to a type acceptable to the predefined operator
       with
    [
           T=char
       ]

I would have thought that the C++ compiler would always deduce T in the
operator*= to be 'char', from the fact that 'ytest' is clearly
'YTestTemplate<char>' and then use XTestChar's char conversion operator
to pass a 'char' to the operator *= function second parameter. Why is
this not allowed ? Are templated operators not allowed to do conversions
when a type is deduced ?