From 8ee39e31bb40aea70afb40611b0cc39d23175552 Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Fri, 4 Mar 2016 21:27:21 +0000
Subject: [PATCH] Implement P0036R0: remove support for empty unary folds of +,
 *, |, &.

llvm-svn: 262747
---
 clang/lib/Sema/SemaTemplateVariadic.cpp            | 15 ---------------
 clang/test/SemaTemplate/cxx1z-fold-expressions.cpp | 15 ++++++++-------
 clang/www/cxx_status.html                          |  2 +-
 3 files changed, 9 insertions(+), 23 deletions(-)

diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp
index cb67d71f..c692c9f 100644
--- a/clang/lib/Sema/SemaTemplateVariadic.cpp
+++ b/clang/lib/Sema/SemaTemplateVariadic.cpp
@@ -996,10 +996,6 @@ ExprResult Sema::BuildEmptyCXXFoldExpr(SourceLocation EllipsisLoc,
                                        BinaryOperatorKind Operator) {
   // [temp.variadic]p9:
   //   If N is zero for a unary fold-expression, the value of the expression is
-  //       *   ->  1
-  //       +   ->  int()
-  //       &   ->  -1
-  //       |   ->  int()
   //       &&  ->  true
   //       ||  ->  false
   //       ,   ->  void()
@@ -1009,17 +1005,6 @@ ExprResult Sema::BuildEmptyCXXFoldExpr(SourceLocation EllipsisLoc,
   // prevent the result from being a null pointer constant.
   QualType ScalarType;
   switch (Operator) {
-  case BO_Add:
-    ScalarType = Context.IntTy;
-    break;
-  case BO_Mul:
-    return ActOnIntegerConstant(EllipsisLoc, 1);
-  case BO_Or:
-    ScalarType = Context.IntTy;
-    break;
-  case BO_And:
-    return CreateBuiltinUnaryOp(EllipsisLoc, UO_Minus,
-                                ActOnIntegerConstant(EllipsisLoc, 1).get());
   case BO_LOr:
     return ActOnCXXBoolLiteral(EllipsisLoc, tok::kw_false);
   case BO_LAnd:
diff --git a/clang/test/SemaTemplate/cxx1z-fold-expressions.cpp b/clang/test/SemaTemplate/cxx1z-fold-expressions.cpp
index 8bb7911..aefee92 100644
--- a/clang/test/SemaTemplate/cxx1z-fold-expressions.cpp
+++ b/clang/test/SemaTemplate/cxx1z-fold-expressions.cpp
@@ -25,10 +25,6 @@ constexpr bool check() {
 static_assert(check());
 
 template<int ...N> void empty() {
-  static_assert((N + ...) == 0);
-  static_assert((N * ...) == 1);
-  static_assert((N | ...) == 0);
-  static_assert((N & ...) == -1);
   static_assert((N || ...) == false);
   static_assert((N && ...) == true);
   (N, ...);
@@ -36,14 +32,19 @@ template<int ...N> void empty() {
 template void empty<>();
 
 // An empty fold-expression isn't a null pointer just because it's an integer
-// with value 0.
+// with value 0. (This is no longer an issue since empty pack expansions don't
+// produce integers any more.)
 template<int ...N> void null_ptr() {
-  void *p = (N + ...); // expected-error {{rvalue of type 'int'}}
-  void *q = (N | ...); // expected-error {{rvalue of type 'int'}}
+  void *p = (N || ...); // expected-error {{rvalue of type 'bool'}}
+  void *q = (N , ...); // expected-error {{rvalue of type 'void'}}
 }
 template void null_ptr<>(); // expected-note {{in instantiation of}}
 
 template<int ...N> void bad_empty() {
+  (N + ...); // expected-error {{empty expansion for operator '+' with no fallback}}
+  (N * ...); // expected-error {{empty expansion for operator '*' with no fallback}}
+  (N | ...); // expected-error {{empty expansion for operator '|' with no fallback}}
+  (N & ...); // expected-error {{empty expansion for operator '&' with no fallback}}
   (N - ...); // expected-error {{empty expansion for operator '-' with no fallback}}
   (N / ...); // expected-error {{empty expansion for operator '/' with no fallback}}
   (N % ...); // expected-error {{empty expansion for operator '%' with no fallback}}
diff --git a/clang/www/cxx_status.html b/clang/www/cxx_status.html
index b2a13ac..f116aee 100644
--- a/clang/www/cxx_status.html
+++ b/clang/www/cxx_status.html
@@ -577,7 +577,7 @@ as the draft C++1z standard evolves.</p>
     </tr>
       <tr> <!-- from Jacksonville -->
         <td><a href="http://wg21.link/p0036r0">P0036R0</a></td>
-        <td class="no" align="center">No</td>
+        <td class="svn" align="center">SVN</td>
       </tr>
     <tr>
       <td><tt>u8</tt> character literals</td>
-- 
2.7.4