Merge pull request #2991 from stan-dev/fix/2989-fabs-adl

Author: WardBrian

stan/math/prim/err/check_symmetric.hpp

@@ -32,6 +32,7 @@ template <typename EigMat, require_matrix_t<EigMat>* = nullptr>
 inline void check_symmetric(const char* function, const char* name,
                             const EigMat& y) {
   check_square(function, name, y);
+  using stan::math::fabs;
   using std::fabs;
 
   Eigen::Index k = y.rows();

test/unit/math/prim/err/check_symmetric_test.cpp

@@ -64,3 +64,14 @@ TEST(ErrorHandlingMatrix, checkSymmetric_non_square) {
   EXPECT_THROW(stan::math::check_symmetric("checkSymmetric", "y", y),
                std::invalid_argument);
 }
+
+TEST(ErrorHandlingMatrix, checkSymmetric_complex) {
+  Eigen::MatrixXcd y(2, 2);
+  y << std::complex<double>(1, 1), std::complex<double>(2, 2),
+      std::complex<double>(2, 2), std::complex<double>(1, 1);
+
+  EXPECT_NO_THROW(stan::math::check_symmetric("checkSymmetric", "y", y));
+  y(0, 1) = std::complex<double>(2, 3);
+  EXPECT_THROW(stan::math::check_symmetric("checkSymmetric", "y", y),
+               std::domain_error);
+}

test/unit/math/prim/fun/fabs_test.cpp

@@ -5,3 +5,9 @@ TEST(primScalFun, fabs) {
   stan::test::expect_common_prim([](auto x) { return std::fabs(x); },
                                  [](auto x) { return stan::math::fabs(x); });
 }
+
+TEST(primScalFun, fabs_complex) {
+  using stan::math::fabs;
+  std::complex<double> z(1.0, 2.0);
+  EXPECT_FLOAT_EQ(fabs(z), 2.236068);
+}