re PR c++/5293 (confusing message when binding a temporary to a reference)

PR c++/5293
* call.c (initialize_reference): Improve diagnostic.

From-SVN: r69332

gcc/cp/ChangeLog

+2003-07-14  Gabriel Dos Reis  <gdr@integrable-solutions.net>
+
+	PR c++/5293
+	* call.c (initialize_reference): Improve diagnostic.
+
 2003-07-14  Kriang Lerdsuwanakij  <lerdsuwa@users.sourceforge.net>
 
 	PR c++/11154

gcc/cp/call.c

@@ -6035,7 +6035,13 @@ initialize_reference (tree type, tree expr, tree decl)
   conv = reference_binding (type, TREE_TYPE (expr), expr, LOOKUP_NORMAL);
   if (!conv || ICS_BAD_FLAG (conv))
     {
-      error ("could not convert `%E' to `%T'", expr, type);
+      if (!(TYPE_QUALS (TREE_TYPE (type)) & TYPE_QUAL_CONST)
+          && !real_lvalue_p (expr))
+        error ("invalid initialization of non-const reference of "
+               "type '%T' from a temporary of type '%T'",
+               type, TREE_TYPE (expr));
+      else
+        error ("could not convert `%E' to `%T'", expr, type);
       return error_mark_node;
     }
 

gcc/testsuite/g++.dg/init/ref8.C

+struct A {
+   A operator=(const A&);
+};
+
+A operator*(A, A);
+
+A& operator+=(A& a, const A& b)
+{
+   return a = a * b;            // { dg-error "non-const reference" }
+}