various problems with template-name template parameters

[Ewgenij Gawrilow]

I've brought several code fragments together, because I thought they are
hitting various bugs in the same corner of the C++ front-end. If I'm in error,
please split the test suite accordingly and excuse me for causing this extra work.

System environment as follows:

% uname -a
SunOS sokol 5.7 Generic_106541-08 sun4u sparc SUNW,UltraSPARC-IIi-Engine

% g++ -v
Using builtin specs.
gcc version 2.95.2 19991024 (release)

% cat tmp/gcc-build/config.status 
#!/bin/sh
# This file was generated automatically by configure.  Do not edit.
# This directory was configured as follows:
.../tmp/gcc-2.95.2/configure --with-gcc-version-trigger=.../tmp/gcc-2.95.2/gcc/version.c --host=sparc-sun-solaris2.6 --enable-shared --enable-version-specific-runtime-libs --enable-languages=c++ --with-gxx-include-dir=/usr/local/include/C++ --norecursion 
# using "mh-frag" and "mt-frag"

********************************************************************************
The actual value of the template-name argument of a member template
gets "spilled" when passed to another template instantiation:

#line 1 "prob4.cc"
template <class T>
struct Op { };

template <template <class X> class Y>
void g() { }

template <class T>
class A {
public:
   template <template <class X> class Y>
   void f() {
      g<Y>();
   }
};

int main() {
   A<int> a;
   a.template f<Op>();
   return 0;
}


prob4.cc: In instantiation of `g<Y>()':
prob4.cc:12:   instantiated from here
prob4.cc:5: Internal compiler error.

********************************************************************************
Here the wrong specialization is being chosen.


#include <iostream>

template <template <class X> class B, class A>
struct is_instance_of {
   enum { answer=false };
};

template <template <class X> class B, class T>
struct is_instance_of<B, B<T> > {
   enum { answer=true };
};

template <class X> struct C { };
template <class X> struct D { };

template <class T>
bool is_C (const T&) {
   return is_instance_of<C,T>::answer;
};

int main() {
   cout << "should be true: " << is_C(C<int>()) << endl;
   cout << "should be false: " << is_C(D<int>()) << endl;
   return 0;
}


The program prints:

should be true: 1
should be false: 1

********************************************************************************
This test case has remained rather long despite of all my trying to strip off
all unnecessary details. Sorry.


#line 1 "prob6.cc"
template <class X, class Y>
class A : public X { };

struct B { };

template <template <class XX, class YY> class Z, class X, class Y>
class C { };

template <class X>
class D { };

template <class X, class Y>
class E : public D<typename X::I> {
public:
   E(const X&, const Y&) { }
};

class F {
public:
   typedef int I;
};

template <class X, class Y>
class G {
public:
   typedef A<X, C<E,F,Y> > R;
   R r() const;
};

class H {
public:
   bool operator== (const H& i2) const;
};

void f()
{
   G<H,B> g1, g2;
   g1.r() == g2.r();
}


prob6.cc: In function `void f()':
prob6.cc:38: Internal compiler error 390.

********************************************************************************
I'm not that sure about the last problem, whether it's caused by a compiler bug 
or just by my imperfect understanding of C++. Although I haven't found the
passage in the Standard explicitly prohibiting the following construction:


#line 1 "prob7.cc"
template <template <class X> class Y>
class A {
public:
   template <class T> class B { };
};

class A2 {
public:
   template <class T> class B { };
};

template <class T> class C { };

template <template <class X> class Y> class D { };

template <template <class X> class Y> void f(int);

void g() {
   D<C> d1;
   f<C>(0);
   A<C>::B<int> a1;
   A2::B<int> a2;
   D<A2::B> d2;
   f<A2::B>(0);
   D<A<C>::B> d3;
   f<A<C>::B>(0);
};


prob7.cc: In function `void g()':
prob7.cc:23: Internal compiler error 980422.

********************************************************************************

With best regards,
Ewgenij Gawrilow
Dept. of Mathematics, Technical University of Berlin