re PR c++/55842 (C++11 ICE with boost multi-precision and boost variant)

	PR c++/55842
	* semantics.c (trait_expr_value): Call maybe_instantiate_noexcept.

From-SVN: r194869

gcc/cp/ChangeLog

 2013-01-03  Jason Merrill  <jason@redhat.com>
 
+	PR c++/55842
+	* semantics.c (trait_expr_value): Call maybe_instantiate_noexcept.
+
 	PR c++/55856
 	* semantics.c (build_data_member_initialization): Handle DECL_EXPR.
 

gcc/cp/semantics.c

@@ -5454,7 +5454,8 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
       return (trait_expr_value (CPTK_HAS_TRIVIAL_CONSTRUCTOR, type1, type2) 
 	      || (CLASS_TYPE_P (type1)
 		  && (t = locate_ctor (type1))
-		  && TYPE_NOTHROW_P (TREE_TYPE (t))));
+		  && (maybe_instantiate_noexcept (t),
+		      TYPE_NOTHROW_P (TREE_TYPE (t)))));
 
     case CPTK_HAS_TRIVIAL_CONSTRUCTOR:
       type1 = strip_array_types (type1);

gcc/testsuite/g++.dg/ext/has_nothrow_constructor-2.C

+// PR c++/55842
+// { dg-options -std=c++11 }
+
+template <class=void> struct number {
+  number() noexcept(noexcept(0)) { }
+};
+const int z=__has_nothrow_constructor(number<>);