From 70a58c577eaf067748c2ec31bfd0b0a614cffba6 Mon Sep 17 00:00:00 2001
From: Rasmus Munk Larsen <rmlarsen@google.com>
Date: Mon, 22 Nov 2021 17:01:35 -0800
Subject: [PATCH] Replace usage of deprecated Eigen class MappedSparseMatrix.
 (#3499)

* Replace usage of deprecated Eigen class

Eigen::MappedSparseMatrix has been deprecated since Eigen 3.3 from 2016. Use the equivalent modern syntax Eigen::Map<Eigen::SparseMatrix<...>>.

* Update eigen.h

* Update eigen.h
---
 include/pybind11/eigen.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index e43e484c6..965d66e8a 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -50,8 +50,12 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 
 #if EIGEN_VERSION_AT_LEAST(3,3,0)
 using EigenIndex = Eigen::Index;
+template<typename Scalar, int Flags, typename StorageIndex>
+using EigenMapSparseMatrix = Eigen::Map<Eigen::SparseMatrix<Scalar, Flags, StorageIndex>>;
 #else
 using EigenIndex = EIGEN_DEFAULT_DENSE_INDEX_TYPE;
+template<typename Scalar, int Flags, typename StorageIndex>
+using EigenMapSparseMatrix = Eigen::MappedSparseMatrix<Scalar, Flags, StorageIndex>;
 #endif
 
 // Matches Eigen::Map, Eigen::Ref, blocks, etc:
@@ -571,9 +575,9 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
         if (!values || !innerIndices || !outerIndices)
             return false;
 
-        value = Eigen::MappedSparseMatrix<Scalar,
-                                          Type::Flags & (Eigen::RowMajor | Eigen::ColMajor),
-                                          StorageIndex>(
+        value = EigenMapSparseMatrix<Scalar,
+                                     Type::Flags & (Eigen::RowMajor | Eigen::ColMajor),
+                                     StorageIndex>(
             shape[0].cast<Index>(), shape[1].cast<Index>(), nnz,
             outerIndices.mutable_data(), innerIndices.mutable_data(), values.mutable_data());