[clang] Persist Attr::IsPackExpansion into the PCH

Summary: Fixes clangd/clangd#309

Subscribers: ilya-biryukov, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77194

(cherry picked from commit 8b3b755)

Author: HighCommander4

clang/test/PCH/cxx-attrs-packexpansion.cpp

@@ -0,0 +1,25 @@
+// Test this without pch.
+// RUN: %clang_cc1 -include %s -emit-llvm -o - %s
+
+// Test with pch.
+// RUN: %clang_cc1 -emit-pch -o %t %s
+// RUN: %clang_cc1 -include-pch %t -emit-llvm -o - %s
+
+#ifndef HEADER
+#define HEADER
+
+template<typename T, typename... Types>
+struct static_variant {
+    alignas(Types...) T storage[10];
+};
+
+#else
+
+struct A {
+    static_variant<int> a;
+};
+struct B {
+    static_variant<A> _b;
+};
+
+#endif

clang/utils/TableGen/ClangAttrEmitter.cpp

@@ -2825,6 +2825,7 @@ void EmitClangAttrPCHRead(RecordKeeper &Records, raw_ostream &OS) {
     if (R.isSubClassOf(InhClass))
       OS << "    bool isInherited = Record.readInt();\n";
     OS << "    bool isImplicit = Record.readInt();\n";
+    OS << "    bool isPackExpansion = Record.readInt();\n";
     ArgRecords = R.getValueAsListOfDefs("Args");
     Args.clear();
     for (const auto *Arg : ArgRecords) {
@@ -2840,6 +2841,7 @@ void EmitClangAttrPCHRead(RecordKeeper &Records, raw_ostream &OS) {
     if (R.isSubClassOf(InhClass))
       OS << "    cast<InheritableAttr>(New)->setInherited(isInherited);\n";
     OS << "    New->setImplicit(isImplicit);\n";
+    OS << "    New->setPackExpansion(isPackExpansion);\n";
     OS << "    break;\n";
     OS << "  }\n";
   }
@@ -2866,6 +2868,7 @@ void EmitClangAttrPCHWrite(RecordKeeper &Records, raw_ostream &OS) {
     if (R.isSubClassOf(InhClass))
       OS << "    Record.push_back(SA->isInherited());\n";
     OS << "    Record.push_back(A->isImplicit());\n";
+    OS << "    Record.push_back(A->isPackExpansion());\n";
 
     for (const auto *Arg : Args)
       createArgument(*Arg, R.getName())->writePCHWrite(OS);