C++ PATCH for c++/48113 (SFINAE bug causing bind regression in libstdc++)

[Jason Merrill <jason at redhat dot com>]

convert_for_initialization is sfinae-enabled, but it was calling 
ocp_convert, which is not.  This patch changes it to use the newer 
perform_implicit_conversion_flags instead.  To make that work, I needed 
to add support for LOOKUP_PREFER_RVALUE to that code path.

Tested x86_64-pc-linux-gnu, applying to trunk.

Also OK for 4.6.0?  The risk is that swapping to 
perform_implicit_conversion_flags will have other differences of 
behavior, but the library regression seems pretty major, so I think it's 
worth the risk.
commit fb46d045ce1b2ee71402942a42b61921cec7c41f
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Mar 14 14:49:58 2011 -0400

    	PR c++/48113
    	* typeck.c (convert_for_initialization): Use
    	perform_implicit_conversion_flags.
    	* call.c (standard_conversion): If LOOKUP_PREFER_RVALUE, set
    	rvaluedness_matches_p on ck_rvalue.
    	(convert_like_real) [ck_rvalue]: And restore it here.

diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index f75c248..436c956 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -98,7 +98,9 @@ struct conversion {
   BOOL_BITFIELD base_p : 1;
   /* If KIND is ck_ref_bind, true when either an lvalue reference is
      being bound to an lvalue expression or an rvalue reference is
-     being bound to an rvalue expression. */
+     being bound to an rvalue expression.  If KIND is ck_rvalue,
+     true when we should treat an lvalue as an rvalue (12.8p33).  If
+     KIND is ck_base, always false.  */
   BOOL_BITFIELD rvaluedness_matches_p: 1;
   BOOL_BITFIELD check_narrowing: 1;
   /* The type of the expression resulting from the conversion.  */
@@ -897,6 +899,8 @@ standard_conversion (tree to, tree from, tree expr, bool c_cast_p,
 	    }
 	}
       conv = build_conv (ck_rvalue, from, conv);
+      if (flags & LOOKUP_PREFER_RVALUE)
+	conv->rvaluedness_matches_p = true;
     }
 
    /* Allow conversion between `__complex__' data types.  */
@@ -5489,6 +5493,8 @@ convert_like_real (conversion *convs, tree expr, tree fn, int argnum,
 	   conversion (i.e. the second step of copy-initialization), so
 	   don't allow any more.  */
 	flags |= LOOKUP_NO_CONVERSION;
+      if (convs->rvaluedness_matches_p)
+	flags |= LOOKUP_PREFER_RVALUE;
       if (TREE_CODE (expr) == TARGET_EXPR
 	  && TARGET_EXPR_LIST_INIT_P (expr))
 	/* Copy-list-initialization doesn't actually involve a copy.  */
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index c062f0f..0e8a6d7 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -7454,7 +7454,7 @@ convert_for_initialization (tree exp, tree type, tree rhs, int flags,
     return rhs;
 
   if (MAYBE_CLASS_TYPE_P (type))
-    return ocp_convert (type, rhs, CONV_IMPLICIT|CONV_FORCE_TEMP, flags);
+    return perform_implicit_conversion_flags (type, rhs, complain, flags);
 
   return convert_for_assignment (type, rhs, errtype, fndecl, parmnum,
 				 complain, flags);
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist38.C b/gcc/testsuite/g++.dg/cpp0x/initlist38.C
index 818d69a..32e20d5 100644
--- a/gcc/testsuite/g++.dg/cpp0x/initlist38.C
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist38.C
@@ -17,5 +17,5 @@ int main()
   f({});
   B b0 = { };
   B b1 { };    // OK, uses #1
-  B b2 { 1 };  // { dg-error "conversion" }
+  B b2 { 1 };  // { dg-error "could not convert" }
 }
diff --git a/gcc/testsuite/g++.dg/cpp0x/pr45908.C b/gcc/testsuite/g++.dg/cpp0x/pr45908.C
index 1a821e5..3a85088 100644
--- a/gcc/testsuite/g++.dg/cpp0x/pr45908.C
+++ b/gcc/testsuite/g++.dg/cpp0x/pr45908.C
@@ -14,5 +14,5 @@ struct vector {
 class block {
     vector v;
     auto end() const -> decltype(v.begin())
-    { return v.begin(); } // { dg-error "conversion" }
+    { return v.begin(); } // { dg-error "could not convert" }
 };
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae6.C b/gcc/testsuite/g++.dg/cpp0x/sfinae6.C
new file mode 100644
index 0000000..401d536
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae6.C
@@ -0,0 +1,31 @@
+// PR c++/48113
+// { dg-options -std=c++0x }
+
+template<typename T> T declval();
+
+struct tuple { };
+
+struct F1
+{
+    void operator()(tuple, int);
+};
+
+typedef void (*F2)(tuple, int);
+
+template<typename F, typename T>
+struct Bind
+{
+    template<typename A,
+             typename R = decltype( F()(declval<T&>(), A()) )>
+    R f(A);
+
+    template<typename A,
+             typename R = decltype( F()(declval<volatile T&>(), A()) )>
+    R f(A) volatile;
+};
+
+int main()
+{
+    Bind<F1, tuple>().f(0);  // OK
+    Bind<F2, tuple>().f(0);  // ERROR, should be OK
+}
diff --git a/gcc/testsuite/g++.old-deja/g++.jason/conversion11.C b/gcc/testsuite/g++.old-deja/g++.jason/conversion11.C
index 607cf9c..6621a27 100644
--- a/gcc/testsuite/g++.old-deja/g++.jason/conversion11.C
+++ b/gcc/testsuite/g++.old-deja/g++.jason/conversion11.C
@@ -21,7 +21,7 @@ void DoSomething(Ding A);
 
 void foo(Something* pX)
 {
-  DoSomething(1);		// { dg-error "conversion" } 
+  DoSomething(1);		// { dg-error "could not convert" }
   pX->DoSomething(1);		// { dg-error "no matching" } 
   // { dg-message "candidate" "candidate note" { target *-*-* } 25 }
   (*pX).DoSomething(1);		// { dg-error "no matching" } 
diff --git a/gcc/testsuite/g++.old-deja/g++.law/arg11.C b/gcc/testsuite/g++.old-deja/g++.law/arg11.C
index fc590c4..fc93579 100644
--- a/gcc/testsuite/g++.old-deja/g++.law/arg11.C
+++ b/gcc/testsuite/g++.old-deja/g++.law/arg11.C
@@ -16,7 +16,7 @@ void function(Ack);
 int
 foo(S *o)
 { // Neither call has a usable constructor for conversions of char[5] to Ack.
-  function("adsf");// { dg-error "conversion" } 
+  function("adsf");// { dg-error "could not convert" }
   o->method("adsf");// { dg-error "no matching" } 
   // { dg-message "candidate" "candidate note" { target *-*-* } 20 }
   return 0;