re PR c++/62255 (Introducing an unrelated template parameter causes compilation to fail)

	PR c++/62255
	* pt.c (instantiate_decl): Handle recursive instantiation of
	static data member.

From-SVN: r215062

gcc/cp/ChangeLog

+2014-09-08  Jason Merrill  <jason@redhat.com>
+
+	PR c++/62255
+	* pt.c (instantiate_decl): Handle recursive instantiation of
+	static data member.
+
 2014-09-05  Jason Merrill  <jason@redhat.com>
 
 	PR c++/62659

gcc/cp/pt.c

@@ -19996,13 +19996,18 @@ instantiate_decl (tree d, int defer_ok,
 			      args,
 			      tf_warning_or_error, NULL_TREE,
 			      /*integral_constant_expression_p=*/false);
-	  /* Make sure the initializer is still constant, in case of
-	     circular dependency (template/instantiate6.C). */
-	  const_init
-	    = DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (code_pattern);
-	  cp_finish_decl (d, init, /*init_const_expr_p=*/const_init,
-			  /*asmspec_tree=*/NULL_TREE,
-			  LOOKUP_ONLYCONVERTING);
+	  /* If instantiating the initializer involved instantiating this
+	     again, don't call cp_finish_decl twice.  */
+	  if (!DECL_INITIAL (d))
+	    {
+	      /* Make sure the initializer is still constant, in case of
+		 circular dependency (template/instantiate6.C). */
+	      const_init
+		= DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (code_pattern);
+	      cp_finish_decl (d, init, /*init_const_expr_p=*/const_init,
+			      /*asmspec_tree=*/NULL_TREE,
+			      LOOKUP_ONLYCONVERTING);
+	    }
 	  if (enter_context)
 	    pop_nested_class ();
 	  pop_nested_namespace (ns);

gcc/testsuite/g++.dg/template/recurse4.C

+// PR c++/62255
+
+// It's not clear whether this is well-formed; instantiating the
+// initializer of 'value' causes the instantiation of Derived, which in
+// turn requires the value of 'value', but the recursion ends there, so it
+// seems reasonable to allow it.
+
+template <typename T> struct Test {
+  template<typename X> static int check(typename X::Type*);
+  template<typename> static char check(...);
+  static const bool value = (sizeof(check<T>(0)) == sizeof(int));
+};
+template <int> struct Sink { };
+template <typename T> struct Derived : Sink<Test<Derived<T> >::value> {
+  typedef int Type;
+};
+
+Sink<Test<Derived<int> >::value> s;