c++: deleted fn and noexcept inst [PR101532, PR104225]

Here when attempting to use B's implicitly deleted default constructor,
mark_used rightfully returns false, but for the wrong reason: it
tries to instantiate the synthesized noexcept specifier which then only
silently fails because get_defaulted_eh_spec suppresses diagnostics
for deleted functions.  This lack of diagnostics causes us to crash on
the first testcase below (thanks to the assert in finish_expr_stmt), and
silently accept the second testcase.

To fix this, this patch makes mark_used avoid attempting to instantiate
the noexcept specifier of a deleted function, so that we'll instead
directly reject (and diagnose) the function due to its deletedness.

	PR c++/101532
	PR c++/104225

gcc/cp/ChangeLog:

	* decl2.cc (mark_used): Don't consider maybe_instantiate_noexcept
	on a deleted function.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/nsdmi-template21.C: New test.
	* g++.dg/cpp0x/nsdmi-template21a.C: New test.

gcc/cp/decl2.cc

@@ -5774,6 +5774,7 @@ mark_used (tree decl, tsubst_flags_t complain)
     used_types_insert (DECL_CONTEXT (decl));
 
   if (TREE_CODE (decl) == FUNCTION_DECL
+      && !DECL_DELETED_FN (decl)
       && !maybe_instantiate_noexcept (decl, complain))
     return false;
 

gcc/testsuite/g++.dg/cpp0x/nsdmi-template21.C

@@ -0,0 +1,8 @@
+// PR c++/101532
+// { dg-do compile { target c++11 } }
+
+struct A { private: ~A(); };
+
+template<class> struct B { A a = A(); }; // { dg-error "private" }
+
+B<int> b; // { dg-error "deleted" }

gcc/testsuite/g++.dg/cpp0x/nsdmi-template21a.C

@@ -0,0 +1,10 @@
+// PR c++/104225
+// { dg-do compile { target c++11 } }
+
+struct A { private: ~A(); };
+
+template<class> struct B { A a = A(); }; // { dg-error "private" }
+
+int main() {
+  new B<int>; // { dg-error "deleted" }
+}