re PR c++/42013 (cv-qualification of conditional expression type depending on…

re PR c++/42013 (cv-qualification of conditional expression type depending on the value of its first expression?!?)

	PR c++/42013
	* call.c (build_conditional_expr): Check specifically for folding
	to CALL_EXPR rather than TREE_SIDE_EFFECTS.

From-SVN: r154129

gcc/cp/ChangeLog

 2009-11-12  Jason Merrill  <jason@redhat.com>
 
+	PR c++/42013
+	* call.c (build_conditional_expr): Check specifically for folding
+	to CALL_EXPR rather than TREE_SIDE_EFFECTS.
+
+2009-11-12  Jason Merrill  <jason@redhat.com>
+
 	* typeck.c (cv_qualified_p): New fn.
 	(decay_conversion): Use it.
 	* cp-tree.h: Declare it.

gcc/cp/call.c

@@ -3605,6 +3605,7 @@ build_conditional_expr (tree arg1, tree arg2, tree arg3,
   tree arg2_type;
   tree arg3_type;
   tree result = NULL_TREE;
+  tree result_save;
   tree result_type = NULL_TREE;
   bool lvalue_p = true;
   struct z_candidate *candidates = 0;
@@ -3991,12 +3992,12 @@ build_conditional_expr (tree arg1, tree arg2, tree arg3,
     }
 
  valid_operands:
-  result = build3 (COND_EXPR, result_type, arg1, arg2, arg3);
+  result_save = build3 (COND_EXPR, result_type, arg1, arg2, arg3);
+  result = fold_if_not_in_template (result_save);
 
-  if (cp_unevaluated_operand && TREE_SIDE_EFFECTS (result))
-    /* Avoid folding a ?: of two calls within decltype (c++/42013).  */;
-  else
-    result = fold_if_not_in_template (result);
+  if (cp_unevaluated_operand && TREE_CODE (result) == CALL_EXPR)
+    /* Avoid folding to a CALL_EXPR within decltype (c++/42013).  */
+    result = result_save;
 
   /* We can't use result_type below, as fold might have returned a
      throw_expr.  */

gcc/testsuite/g++.dg/cpp0x/decltype19.C

@@ -2,7 +2,7 @@
 
 template<typename _Tp>
   _Tp
-declval();
+__attribute ((const)) declval();
 
 template<typename _Tp, typename _Up>
   struct common_type