[Clang] Preserve partially substituted pack indexing type/expressions (#116782)

Substituting into pack indexing types/expressions can still result in
unexpanded types/expressions, such as `PackIndexingType` or
`PackIndexingExpr`. To handle these cases correctly, we should defer the
pack size checks to the next round of transformation, when the patterns
can be fully expanded.

To that end, the `FullySubstituted` flag is now necessary for computing
the dependencies of `PackIndexingExprs`. Conveniently, this flag can
also represent the prior `ExpandsToEmpty` status with an additional
emptiness check. Therefore, I converted all stored flags to use
`FullySubstituted`.

Fixes https://github.com/llvm/llvm-project/issues/116105

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/lib/Serialization/ASTWriterStmt.cpp b/clang/lib/Serialization/ASTWriterStmt.cpp
index e7f567f..4994047 100644
--- a/clang/lib/Serialization/ASTWriterStmt.cpp
+++ b/clang/lib/Serialization/ASTWriterStmt.cpp
@@ -2191,7 +2191,7 @@ void ASTStmtWriter::VisitSizeOfPackExpr(SizeOfPackExpr *E) {
 void ASTStmtWriter::VisitPackIndexingExpr(PackIndexingExpr *E) {
   VisitExpr(E);
   Record.push_back(E->TransformedExpressions);
-  Record.push_back(E->ExpandedToEmptyPack);
+  Record.push_back(E->FullySubstituted);
   Record.AddSourceLocation(E->getEllipsisLoc());
   Record.AddSourceLocation(E->getRSquareLoc());
   Record.AddStmt(E->getPackIdExpression());