[LLVM][PDB] Use IsUnsigned flag for APInt correctly (llvm#131598)

This patch fixes an assertion that occurs in `APInt`.

The assertion can be reproduced with LLDB test
`python_api/thread/TestThreadAPI.py` (it fails).

Author: AlexK0

llvm/include/llvm/DebugInfo/PDB/PDBTypes.h

@@ -510,7 +510,9 @@ struct Variant {
 
 #define VARIANT_APSINT(Enum, NumBits, IsUnsigned)                              \
   case PDB_VariantType::Enum:                                                  \
-    return APSInt(APInt(NumBits, Value.Enum), IsUnsigned);
+    return APSInt(                                                             \
+        APInt(NumBits, static_cast<uint64_t>(Value.Enum), !IsUnsigned),        \
+        IsUnsigned);
 
   APSInt toAPSInt() const {
     switch (Type) {

llvm/unittests/DebugInfo/PDB/CMakeLists.txt

@@ -10,6 +10,7 @@ add_llvm_unittest_with_input_files(DebugInfoPDBTests
   NativeSymbolReuseTest.cpp
   StringTableBuilderTest.cpp
   PDBApiTest.cpp
+  PDBVariantTest.cpp
   )
 
 target_link_libraries(DebugInfoPDBTests PRIVATE LLVMTestingSupport)

llvm/unittests/DebugInfo/PDB/PDBVariantTest.cpp

@@ -0,0 +1,60 @@
+//===- llvm/unittest/DebugInfo/PDB/PDBVariantTest.cpp ---------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "gtest/gtest.h"
+
+#include "llvm/DebugInfo/PDB/PDBTypes.h"
+
+using namespace llvm;
+using namespace llvm::pdb;
+
+namespace {
+
+template <typename T> class PDBVariantIntegerTest : public testing::Test {
+public:
+  std::vector<T> getTestIntegers() {
+    if constexpr (std::is_same_v<T, bool>) {
+      return {true, false};
+    } else {
+      std::vector<T> Integers{0, 1, 32, std::numeric_limits<T>::min(),
+                              std::numeric_limits<T>::max()};
+      if constexpr (std::is_signed_v<T>) {
+        Integers.emplace_back(-1);
+        Integers.emplace_back(-65);
+      }
+      return Integers;
+    }
+  }
+};
+
+using TestTypes = testing::Types<bool, int8_t, uint8_t, int16_t, uint16_t,
+                                 int32_t, uint32_t, int64_t, uint64_t>;
+
+} // namespace
+
+TYPED_TEST_SUITE(PDBVariantIntegerTest, TestTypes);
+
+TYPED_TEST(PDBVariantIntegerTest, ToAPSInt) {
+  for (TypeParam IntegerValue : this->getTestIntegers()) {
+    const Variant VariantValue(IntegerValue);
+
+    const APSInt APSIntValue = VariantValue.toAPSInt();
+    EXPECT_EQ(APSIntValue.isSigned(), std::is_signed_v<TypeParam>)
+        << "Unexpected 'isSigned()' result for '" << IntegerValue << "'";
+    bool IsNegative = false;
+    if constexpr (!std::is_same_v<TypeParam, bool>) {
+      IsNegative = IntegerValue < 0;
+    }
+    EXPECT_EQ(APSIntValue.isNegative(), IsNegative)
+        << "Unexpected 'isNegative()' result for '" << IntegerValue << "'";
+
+    SmallString<20> String;
+    APSIntValue.toString(String);
+    EXPECT_EQ(String.str().str(), std::to_string(IntegerValue));
+  }
+}