Add readability-else-after-return check

.clang-tidy

@@ -2,5 +2,5 @@
 #
 # SPDX-License-Identifier: MIT
 ---
-Checks:              '-*,bugprone-branch-clone,bugprone-reserved-identifier,hicpp-avoid-c-arrays,misc-const-correctness,modernize-use-nullptr,readability-avoid-const-params-in-decls'
+Checks:              '-*,bugprone-branch-clone,bugprone-reserved-identifier,hicpp-avoid-c-arrays,misc-const-correctness,modernize-use-nullptr,readability-avoid-const-params-in-decls,readability-else-after-return'
 WarningsAsErrors:    '*'

include/ddc/kernels/splines/spline_boundary_conditions.hpp

@@ -53,7 +53,9 @@ constexpr int n_boundary_equations(ddc::BoundCond const bc, std::size_t const de
 {
     if (bc == ddc::BoundCond::PERIODIC || bc == ddc::BoundCond::GREVILLE) {
         return 0;
-    } else if (bc == ddc::BoundCond::HERMITE) {
+    }
+
+    if (bc == ddc::BoundCond::HERMITE) {
         return degree / 2;
     }
 

include/ddc/kernels/splines/splines_linear_problem_2x2_blocks.hpp

@@ -151,13 +151,17 @@ class SplinesLinearProblem2x2Blocks : public SplinesLinearProblem<ExecSpace>
         std::size_t const nq = m_top_left_block->size();
         if (i < nq && j < nq) {
             return m_top_left_block->get_element(i, j);
-        } else if (i >= nq && j >= nq) {
+        }
+
+        if (i >= nq && j >= nq) {
             return m_bottom_right_block->get_element(i - nq, j - nq);
-        } else if (j >= nq) {
+        }
+
+        if (j >= nq) {
             return m_top_right_block.h_view(i, j - nq);
-        } else {
-            return m_bottom_left_block.h_view(i - nq, j);
         }
+
+        return m_bottom_left_block.h_view(i - nq, j);
     }
 
     void set_element(std::size_t const i, std::size_t const j, double const aij) override

include/ddc/kernels/splines/splines_linear_problem_band.hpp

@@ -105,9 +105,9 @@ class SplinesLinearProblemBand : public SplinesLinearProblem<ExecSpace>
                                 static_cast<std::ptrdiff_t>(j) - static_cast<std::ptrdiff_t>(m_ku))
             && i < std::min(size(), j + m_kl + 1)) {
             return m_q.h_view(band_storage_row_index(i, j), j);
-        } else {
-            return 0.0;
         }
+
+        return 0.0;
     }
 
     void set_element(std::size_t const i, std::size_t const j, double const aij) override

include/ddc/kernels/splines/splines_linear_problem_maker.hpp

@@ -61,13 +61,17 @@ class SplinesLinearProblemMaker
     {
         if (kl == ku && kl == 1 && pds) {
             return std::make_unique<SplinesLinearProblemPDSTridiag<ExecSpace>>(n);
-        } else if (kl == ku && pds) {
+        }
+
+        if (kl == ku && pds) {
             return std::make_unique<SplinesLinearProblemPDSBand<ExecSpace>>(n, kl);
-        } else if (2 * kl + ku + 1 >= n) {
+        }
+
+        if (2 * kl + ku + 1 >= n) {
             return std::make_unique<SplinesLinearProblemDense<ExecSpace>>(n);
-        } else {
-            return std::make_unique<SplinesLinearProblemBand<ExecSpace>>(n, kl, ku);
         }
+
+        return std::make_unique<SplinesLinearProblemBand<ExecSpace>>(n, kl, ku);
     }
 
     /**

include/ddc/kernels/splines/splines_linear_problem_pds_band.hpp

@@ -75,11 +75,12 @@ class SplinesLinearProblemPDSBand : public SplinesLinearProblem<ExecSpace>
         if (i > j) {
             std::swap(i, j);
         }
+
         if (j - i < m_q.extent(0)) {
             return m_q.h_view(j - i, i);
-        } else {
-            return 0.0;
         }
+
+        return 0.0;
     }
 
     void set_element(std::size_t i, std::size_t j, double const aij) override

include/ddc/kernels/splines/splines_linear_problem_pds_tridiag.hpp

@@ -73,11 +73,12 @@ class SplinesLinearProblemPDSTridiag : public SplinesLinearProblem<ExecSpace>
         if (i > j) {
             std::swap(i, j);
         }
+
         if (j - i < 2) {
             return m_q.h_view(j - i, i);
-        } else {
-            return 0.0;
         }
+
+        return 0.0;
     }
 
     void set_element(std::size_t i, std::size_t j, double const aij) override