update var operators

Author: SteveBronder

stan/math/rev/core/matrix_vari.hpp

@@ -17,7 +17,7 @@ class op_matrix_vari : public vari {
   vari** vis_;
 
  public:
-  template <typename T, require_eigen_vt<is_var, T>...>
+  template <typename T, require_eigen_vt<is_var, T>* = nullptr>
   op_matrix_vari(double f, const T& vs) : vari(f), size_(vs.size()) {
     vis_ = ChainableStack::instance_->memalloc_.alloc_array<vari*>(size_);
     Eigen::Map<Eigen::Matrix<vari*, -1, -1>>(vis_, vs.rows(), vs.cols())

stan/math/rev/core/operator_divide_equal.hpp

@@ -12,7 +12,7 @@ inline var& var::operator/=(var b) {
   return *this;
 }
 
-template <typename Arith, require_arithmetic_t<Arith>* = nullptr>
+template <typename Arith, require_arithmetic_t<Arith>*>
 inline var& var::operator/=(Arith b) {
   if (b == 1.0) {
     return *this;

stan/math/rev/core/operator_minus_equal.hpp

@@ -13,7 +13,7 @@ inline var& var::operator-=(var b) {
   return *this;
 }
 
-template <typename Arith, require_arithmetic_t<Arith>* = nullptr>
+template <typename Arith, require_arithmetic_t<Arith>*>
 inline var& var::operator-=(Arith b) {
   if (b == 0.0) {
     return *this;

stan/math/rev/core/operator_multiply_equal.hpp

@@ -13,7 +13,7 @@ inline var& var::operator*=(var b) {
   return *this;
 }
 
-template <typename Arith, require_arithmetic_t<Arith>* = nullptr>
+template <typename Arith, require_arithmetic_t<Arith>*>
 inline var& var::operator*=(Arith b) {
   if (b == 1.0) {
     return *this;

stan/math/rev/core/operator_plus_equal.hpp

@@ -13,7 +13,7 @@ inline var& var::operator+=(var b) {
   return *this;
 }
 
-template <typename Arith, require_arithmetic_t<Arith>* = nullptr>
+template <typename Arith, require_arithmetic_t<Arith>*>
 inline var& var::operator+=(Arith b) {
   if (b == 0.0) {
     return *this;

stan/math/rev/core/vector_vari.hpp

@@ -15,8 +15,8 @@ class op_vector_vari : public vari {
   vari** vis_;
 
  public:
-  template <typename Arith, typename VecVar, require_arithmetic_t<Arith>...,
-            require_vector_like_vt<is_var, VecVar>...>
+  template <typename Arith, typename VecVar, require_arithmetic_t<Arith>* = nullptr,
+            require_vector_like_vt<is_var, VecVar>* = nullptr>
   op_vector_vari(Arith f, VecVar&& vs) : vari(f), size_(vs.size()) {
     vis_ = reinterpret_cast<vari**>(operator new(sizeof(vari*) * vs.size()));
     for (size_t i = 0; i < vs.size(); ++i) {