[c++20] P0780R2: Support pack-expansion of init-captures.

This permits an init-capture to introduce a new pack:

  template<typename ...T> auto x = [...a = T()] { /* a is a pack */ };

To support this, the mechanism for allowing ParmVarDecls to be packs has
been extended to support arbitrary local VarDecls.

llvm-svn: 361300
diff --git a/clang/lib/Serialization/ASTReaderStmt.cpp b/clang/lib/Serialization/ASTReaderStmt.cpp
index c1e971e..e0647fc 100644
--- a/clang/lib/Serialization/ASTReaderStmt.cpp
+++ b/clang/lib/Serialization/ASTReaderStmt.cpp
@@ -1803,9 +1803,9 @@
   E->NumParameters = Record.readInt();
   E->ParamPack = ReadDeclAs<ParmVarDecl>();
   E->NameLoc = ReadSourceLocation();
-  auto **Parms = E->getTrailingObjects<ParmVarDecl *>();
+  auto **Parms = E->getTrailingObjects<VarDecl *>();
   for (unsigned i = 0, n = E->NumParameters; i != n; ++i)
-    Parms[i] = ReadDeclAs<ParmVarDecl>();
+    Parms[i] = ReadDeclAs<VarDecl>();
 }
 
 void ASTStmtReader::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) {