[llvm] r345411 - [ADT] Use explicit constructors for DenseMapPair to work around compiler issues.

[Lang Hames via llvm-commits]

Author: lhames
Date: Fri Oct 26 10:48:50 2018
New Revision: 345411

URL: http://llvm.org/viewvc/llvm-project?rev=345411&view=rev
Log:
[ADT] Use explicit constructors for DenseMapPair to work around compiler issues.

Inheriting constructors from std::pair caused clang-3.8 to treat some DenseMap
initializer_list constructor calls as ambiguous, which broke several bots. This
commit explicitly defines DenseMapPair's constructos to work around the issue.

https://reviews.llvm.org/D53726

Modified:
    llvm/trunk/include/llvm/ADT/DenseMap.h

Modified: llvm/trunk/include/llvm/ADT/DenseMap.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/DenseMap.h?rev=345411&r1=345410&r2=345411&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/DenseMap.h (original)
+++ llvm/trunk/include/llvm/ADT/DenseMap.h Fri Oct 26 10:48:50 2018
@@ -40,7 +40,32 @@ namespace detail {
 template <typename KeyT, typename ValueT>
 struct DenseMapPair : public std::pair<KeyT, ValueT> {
 
-  using std::pair<KeyT, ValueT>::pair;
+  // FIXME: Switch to inheriting constructors when we drop support for older
+  //        clang versions.
+  // NOTE: This default constructor is declared with '{}' rather than
+  //       '= default' to work around a separate bug in clang-3.8. This can
+  //       also go when we switch to inheriting constructors.
+  DenseMapPair() {}
+
+  DenseMapPair(const KeyT &Key, const ValueT &Value)
+      : std::pair<KeyT, ValueT>(Key, Value) {}
+
+  DenseMapPair(KeyT &&Key, ValueT &&Value)
+      : std::pair<KeyT, ValueT>(std::move(Key), std::move(Value)) {}
+
+  template <typename AltKeyT, typename AltValueT>
+  DenseMapPair(AltKeyT &&AltKey, AltValueT &&AltValue,
+               typename std::enable_if<
+                   std::is_convertible<AltKeyT, KeyT>::value &&
+                   std::is_convertible<AltValueT, ValueT>::value>::type * = 0)
+      : std::pair<KeyT, ValueT>(std::forward<AltKeyT>(AltKey),
+                                std::forward<AltValueT>(AltValue)) {}
+
+  template <typename AltPairT>
+  DenseMapPair(AltPairT &&AltPair,
+               typename std::enable_if<std::is_convertible<
+                   AltPairT, std::pair<KeyT, ValueT>>::value>::type * = 0)
+      : std::pair<KeyT, ValueT>(std::forward<AltPairT>(AltPair)) {}
 
   KeyT &getFirst() { return std::pair<KeyT, ValueT>::first; }
   const KeyT &getFirst() const { return std::pair<KeyT, ValueT>::first; }