Deserialize LValuePathSerializationHelper's type properly

Close llvm#58716.

Tested with libcxx's modules build.

When we read the type of
LValuePathSerializationHelper, we didn't read the correct type. We read
the element type as its name suggests. But the problem here is that it
looks like that both the usage and serialization use its type as the
top level type. So here is the mismatch.

Actually, the type of LValuePathSerializationHelper is never used after
Deserialization without the assertion. So it doesn't matter for the
release users. And this patch shouldn't change the behavior too.

Reviewed By: erichkeane

Differential Revision: https://reviews.llvm.org/D139406

Author: ChuanqiXu9

clang/include/clang/AST/APValue.h

@@ -238,7 +238,7 @@ class APValue {
     }
   };
   class LValuePathSerializationHelper {
-    const void *ElemTy;
+    const void *Ty;
 
   public:
     ArrayRef<LValuePathEntry> Path;

clang/include/clang/AST/AbstractBasicReader.h

@@ -190,7 +190,8 @@ class DataStreamBasicReader : public BasicReaderBase<Impl> {
 
   APValue::LValuePathSerializationHelper readLValuePathSerializationHelper(
       SmallVectorImpl<APValue::LValuePathEntry> &path) {
-    auto elemTy = asImpl().readQualType();
+    auto origTy = asImpl().readQualType();
+    auto elemTy = origTy;
     unsigned pathLength = asImpl().readUInt32();
     for (unsigned i = 0; i < pathLength; ++i) {
       if (elemTy->template getAs<RecordType>()) {
@@ -208,7 +209,7 @@ class DataStreamBasicReader : public BasicReaderBase<Impl> {
             APValue::LValuePathEntry::ArrayIndex(asImpl().readUInt32()));
       }
     }
-    return APValue::LValuePathSerializationHelper(path, elemTy);
+    return APValue::LValuePathSerializationHelper(path, origTy);
   }
 
   Qualifiers readQualifiers() {

clang/lib/AST/APValue.cpp

@@ -156,10 +156,10 @@ void APValue::LValuePathEntry::Profile(llvm::FoldingSetNodeID &ID) const {
 
 APValue::LValuePathSerializationHelper::LValuePathSerializationHelper(
     ArrayRef<LValuePathEntry> Path, QualType ElemTy)
-    : ElemTy((const void *)ElemTy.getTypePtrOrNull()), Path(Path) {}
+    : Ty((const void *)ElemTy.getTypePtrOrNull()), Path(Path) {}
 
 QualType APValue::LValuePathSerializationHelper::getType() {
-  return QualType::getFromOpaquePtr(ElemTy);
+  return QualType::getFromOpaquePtr(Ty);
 }
 
 namespace {