message: Declaring _const_ MustBeCSTSymbolOrNode to silence unused variable warning.
diff: @@ -106,7 +106,7 @@ struct MustBeCSTSymbolOrNode {
  template <typename E, typename S>
  typename match_const<SyntaxTreeNode, S>::type& CheckSymbolAsNode(S& symbol,
  E node_enum) {
  - MustBeCSTSymbolOrNode<S> check;
  + const MustBeCSTSymbolOrNode<S> check;
  return CheckNodeEnum(SymbolCastToNode(symbol), node_enum);
  }
  @@ -163,7 +163,7 @@ const SyntaxTreeLeaf* CheckOptionalSymbolAsLeaf(const std::nullptr_t& symbol,
  template <typename E, typename S>
  typename match_const<Symbol, S>::type* GetSubtreeAsSymbol(
  S& symbol, E parent_must_be_node_enum, size_t child_position) {
  - MustBeCSTSymbolOrNode<S> check;
  + const MustBeCSTSymbolOrNode<S> check;
  return CheckNodeEnum(SymbolCastToNode(symbol),
  parent_must_be_node_enum)[child_position]
  .get();
  @@ -175,7 +175,7 @@ typename match_const<Symbol, S>::type* GetSubtreeAsSymbol(
  template <class S, class E>
  typename match_const<SyntaxTreeNode, S>::type& GetSubtreeAsNode(
  S& symbol, E parent_must_be_node_enum, size_t child_position) {
  - MustBeCSTSymbolOrNode<S> check;
  + const MustBeCSTSymbolOrNode<S> check;
  return SymbolCastToNode(*ABSL_DIE_IF_NULL(
  GetSubtreeAsSymbol(symbol, parent_must_be_node_enum, child_position)));
  }
  @@ -187,7 +187,7 @@ template <class S, class E>
  typename match_const<SyntaxTreeNode, S>::type& GetSubtreeAsNode(
  S& symbol, E parent_must_be_node_enum, size_t child_position,
  E child_must_be_node_enum) {
  - MustBeCSTSymbolOrNode<S> check;
  + const MustBeCSTSymbolOrNode<S> check;
  return CheckNodeEnum(
  GetSubtreeAsNode(symbol, parent_must_be_node_enum, child_position),
  child_must_be_node_enum);
  @@ -198,7 +198,7 @@ template <class S, class E>
  const SyntaxTreeLeaf& GetSubtreeAsLeaf(const S& symbol,
  E parent_must_be_node_enum,
  size_t child_position) {
  - MustBeCSTSymbolOrNode<S> check;
  + const MustBeCSTSymbolOrNode<S> check;
  return SymbolCastToLeaf(*ABSL_DIE_IF_NULL(
  GetSubtreeAsSymbol(symbol, parent_must_be_node_enum, child_position)));
  }
  @@ -206,7 +206,7 @@ const SyntaxTreeLeaf& GetSubtreeAsLeaf(const S& symbol,
  template <class S, class E>
  E GetSubtreeNodeEnum(const S& symbol, E parent_must_be_node_enum,
  size_t child_position) {
  - MustBeCSTSymbolOrNode<S> check;
  + const MustBeCSTSymbolOrNode<S> check;
  return static_cast<E>(
  GetSubtreeAsNode(symbol, parent_must_be_node_enum, child_position)
  .Tag()
  