Fix a bunch of clang warnings (including a dangerous one)

src/language/ast/ASTBuilder.cpp

@@ -54,7 +54,7 @@ struct ASTBuilder::rearrange_pre_unary_op : TAO_PEGTL_NAMESPACE::parse_tree::app
 {
   template <typename... States>
   static void
-  transform(std::unique_ptr<ASTNode>& n, States&&... st)
+  transform(std::unique_ptr<ASTNode>& n, States&&...)
   {
     if (n->children.size() == 1) {
       n = std::move(n->children.back());

src/language/node_processor/FunctionProcessor.hpp

@@ -26,7 +26,8 @@ class FunctionExpressionProcessor final : public INodeProcessor
     } else if constexpr (std::is_same_v<ExpressionValueType, ZeroType>) {
       return ReturnType{ZeroType::zero};
     } else if constexpr (std::is_convertible_v<ExpressionValueType, ReturnType>) {
-      const ExpressionValueType& v = std::get<ExpressionValueType>(m_function_expression.execute(exec_policy));
+      auto expression_value        = m_function_expression.execute(exec_policy);
+      const ExpressionValueType& v = std::get<ExpressionValueType>(expression_value);
       if constexpr (std::is_same_v<ReturnType, uint64_t> and std::is_same_v<ExpressionValueType, int64_t>) {
         if (v < 0) {
           throw std::domain_error("trying to convert negative value (" + stringify(v) + ")");