c++: non-dep array list-init w/ non-triv dtor [PR109899]

The get_target_expr call added in r12-7069-g119cea98f66476 causes us
for the below testcase to call build_vec_delete in a template context,
which builds a templated destructor call and checks expr_noexcept_p for
it, which ICEs because the call has templated form.

Much of the work of build_vec_delete however is code generation and thus
will just get discarded in a template context, and that includes the
code guarded by expr_noexcept_p.  So this patch narrowly fixes this ICE
by eliding the expr_noexcept_p call when in a template context.

	PR c++/109899

gcc/cp/ChangeLog:

	* init.cc (build_vec_delete_1): Assume expr_noexcept_p returns
	false in a template context.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/initlist-array21.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>

gcc/cp/init.cc

@@ -4155,7 +4155,8 @@ build_vec_delete_1 (location_t loc, tree base, tree maxindex, tree type,
 
   /* If one destructor throws, keep trying to clean up the rest, unless we're
      already in a build_vec_init cleanup.  */
-  if (flag_exceptions && !in_cleanup && !expr_noexcept_p (tmp, tf_none))
+  if (flag_exceptions && !in_cleanup && !processing_template_decl
+      && !expr_noexcept_p (tmp, tf_none))
     {
       loop = build2 (TRY_CATCH_EXPR, void_type_node, loop,
 		     unshare_expr (loop));

gcc/testsuite/g++.dg/cpp0x/initlist-array21.C

@@ -0,0 +1,12 @@
+// PR c++/109899
+// { dg-do compile { target c++11 } }
+
+struct A { A(); ~A(); };
+
+template<class T>
+using array = T[42];
+
+template<class T>
+void f() {
+  array<A>{};
+}