Re: template argument required

[Patrick Rammelt]

Larry I Smith wrote:
> Patrick Rammelt wrote:
>
> > Hi
> >
> > I have just upgraded from gcc-3.3.3 to gcc-4.0.0 Trying to compile some
> > old code I stumbled over an error. I created this short example:
> >
> > -------------------- gcctest.cpp -----------------------------
> > #include <iostream>
> >
> > using namespace ::std;
> >
> > template <class T>
> > class A {
> > public:
> >
> >   A (void) {}
> >
> >   template <class X>
> >   class A& foo (X p) {         // no error without "class"
> >     cout << "template foo\n";
> >     return(*this);
> >   }
> >
> > };
> >
> > int main (void) {
> >
> >   A<double> a1, a2;
> >   a1.foo(a2);                  // line 22: error (see below)
> >
> >   exit(0);
> > }
> > --------------------------------------------------------------------
> >
> > no errors when compiling it with g++-3.3.3, but g++-4.0.0 (and 
> > g++-3.4.1) complaints:
> >
> > gcctest.cpp: In function ‘int main()’:
> > gcctest.cpp:22: error: template argument required for ‘struct A’
> > gcctest.cpp:22: error: no matching function for call to
> >                 ‘A<double>::foo(A<double>&)’
> >
> > Substituting "class A&" by just "A&" in foo it compiles without any 
> > warnings or errors (and works as expected). Does this make any sense, 
> > or is it a bug?
>
> The definition of foo() is ambiguous.
> Does this fix it?
>
>    template <class X>
>    class A<T> & foo (X p) {         // <-- specify WHICH type of 'A'
>      cout << "template foo\n";
>      return(*this);
>    }

Yes it does - Thanks! My fix was to leave away the "class", but this 
solution looks better. It really _looks_ better because my editor 
/needs/ the "class" for syntax-highlighting :-)
I'm just curious: is there a reason why the keyword "class" makes a 
difference here - or should there occure an error either in both cases 
or not at all? At least I think the error-message (pointing to line 22) 
is a bit misleading here?!

Ciao,
Patrick
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