Fix PointerIntPair so that it can use an enum class as its integer template argument.

[gottesmm]

Summary

The problem here is that an enum class can not be implicitly converted to an
integer. That assumption snuck back into PointerIntPair. This commit fixes the
issue and more importantly adds some unittests to make sure that we do not break
this again.

rdar://23594806

[gottesmm]

Removed an unneeded static cast.

[gribozavr]

LGTM, thanks Michael!

include/llvm/ADT/PointerIntPair.h

public:
   PointerIntPair() : Value(0) {}
   PointerIntPair(PointerTy PtrVal, IntType IntVal) {
     setPointerAndInt(PtrVal, IntVal);
   }
   explicit PointerIntPair(PointerTy PtrVal) { initWithPointer(PtrVal); }
 
   PointerTy getPointer() const { return Info::getPointer(Value); }
 
-  IntType getInt() const { return (IntType)Info::getInt(Value); }
+  IntType getInt() const {
+    return (IntType)Info::getInt(Value);
+  }
 
   void setPointer(PointerTy PtrVal) {
     Value = Info::updatePointer(Value, PtrVal);
   }
 
-  void setInt(IntType IntVal) { Value = Info::updateInt(Value, IntVal); }
+  void setInt(IntType IntVal) {
+    Value = Info::updateInt(Value, static_cast<intptr_t>(IntVal));
+  }
 
   void initWithPointer(PointerTy PtrVal) {
     Value = Info::updatePointer(0, PtrVal);
   }
 
   void setPointerAndInt(PointerTy PtrVal, IntType IntVal) {
-    Value = Info::updateInt(Info::updatePointer(0, PtrVal), IntVal);
+    Value = Info::updateInt(Info::updatePointer(0, PtrVal),
+                            static_cast<intptr_t>(IntVal));
   }
 
   PointerTy const *getAddrOfPointer() const {
     return const_cast<PointerIntPair *>(this)->getAddrOfPointer();
   }
 
   PointerTy *getAddrOfPointer() {
     assert(Value == reinterpret_cast<intptr_t>(getPointer()) &&

unittests/ADT/PointerIntPairTest.cpp

TEST(PointerIntPairTest, GetSet) {
 
   Pair.setPointer(nullptr);
   EXPECT_EQ(nullptr, Pair.getPointer());
   EXPECT_EQ(2U, Pair.getInt());
 
   Pair.setPointerAndInt(&s, 3U);
   EXPECT_EQ(&s, Pair.getPointer());
   EXPECT_EQ(3U, Pair.getInt());
+
+  // Make sure that we can perform all of our operations on enum classes.
+  //
+  // The concern is that enum classes are only explicitly convertible to
+  // integers. This means that if we assume in PointerIntPair this, a
+  // compilation error will result. This group of tests exercises the enum class
+  // code to make sure that we do not run into such issues in the future.
+  enum class E : unsigned {
+    Case1,
+    Case2,
+    Case3,
+  };
+  PointerIntPair<S *, 2, E> Pair2(&s, E::Case1);
+  EXPECT_EQ(&s, Pair2.getPointer());
+  EXPECT_EQ(E::Case1, Pair2.getInt());
+
+  Pair2.setInt(E::Case2);
+  EXPECT_EQ(&s, Pair2.getPointer());
+  EXPECT_EQ(E::Case2, Pair2.getInt());
+
+  Pair2.setPointer(nullptr);
+  EXPECT_EQ(nullptr, Pair2.getPointer());
+  EXPECT_EQ(E::Case2, Pair2.getInt());
+
+  Pair2.setPointerAndInt(&s, E::Case3);
+  EXPECT_EQ(&s, Pair2.getPointer());
+  EXPECT_EQ(E::Case3, Pair2.getInt());
 }
 
 TEST(PointerIntPairTest, DefaultInitialize) {
   PointerIntPair<float *, 2> Pair;
   EXPECT_EQ(nullptr, Pair.getPointer());
   EXPECT_EQ(0U, Pair.getInt());
 }