Fix warnings created by other warnings fix

Eigen/src/Core/util/Meta.h

diff --git a/Eigen/src/Core/util/Meta.h b/Eigen/src/Core/util/Meta.h
index a45df7e..80c893d 100644
--- a/Eigen/src/Core/util/Meta.h
+++ b/Eigen/src/Core/util/Meta.h
@@ -639,7 +639,7 @@
 constexpr bool is_int_or_enum_v = std::is_enum<A>::value || std::is_integral<A>::value;
 
 template <typename A, typename B>
-inline constexpr void plain_enum_asserts(A a, B b) {
+inline constexpr void plain_enum_asserts(A, B) {
   static_assert(is_int_or_enum_v<A>, "Argument a must be an integer or enum");
   static_assert(is_int_or_enum_v<B>, "Argument b must be an integer or enum");
 }