c++: Fix ICE with defaulted destructor and template.

In a template we don't instantiate a deferred noexcept-spec, and we don't
need it because we aren't going to do anything with the value of
throwing_cleanup in a template anyway.

	PR c++/93345 - ICE with defaulted dtor and template.
	PR c++/33799
	* decl.c (cxx_maybe_build_cleanup): Don't try to set
	throwing_cleanup in a template.

gcc/cp/ChangeLog

+2020-01-23  Jason Merrill  <jason@redhat.com>
+
+	PR c++/93345 - ICE with defaulted dtor and template.
+	PR c++/33799
+	* decl.c (cxx_maybe_build_cleanup): Don't try to set
+	throwing_cleanup in a template.
+
 2020-01-22  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/92907 - noexcept does not consider "const" in member functions.

gcc/cp/decl.c

@@ -17393,7 +17393,8 @@ cxx_maybe_build_cleanup (tree decl, tsubst_flags_t complain)
       && !mark_used (decl, complain) && !(complain & tf_error))
     return error_mark_node;
 
-  if (cleanup && cfun && !expr_noexcept_p (cleanup, tf_none))
+  if (cleanup && cfun && !processing_template_decl
+      && !expr_noexcept_p (cleanup, tf_none))
     cp_function_chain->throwing_cleanup = true;
 
   return cleanup;

gcc/testsuite/g++.dg/cpp0x/initlist-cleanup1.C

+// PR c++/93345
+// { dg-do compile { target c++11 } }
+
+struct ln {
+  ~ln ();
+};
+
+struct ry {
+  ln kj;
+};
+
+template<typename GC>
+void
+dz ()
+{
+  ry{};
+}