BUG: Replace hard-coded itkeigen/ path in itkSpecialFunctions.h

[blowekamp]

Fix the remaining hard-coded itkeigen/unsupported/Eigen/SpecialFunctions include in itkSpecialFunctions.h that breaks compilation when ITK_USE_SYSTEM_EIGEN=ON.

Replaces the path with ITK_EIGEN_UNSUPPORTED(SpecialFunctions) and adds the required #include "itk_eigen.h", consistent with the fix in commit 8543e2f that addressed the same pattern in itkMatrixExponential.h, itkEigenLevenbergMarquardtEngine.cxx, and vnl_levenberg_marquardt.cxx.

AI assistance

• GitHub Copilot (Claude Sonnet 4.6) identified this remaining instance by searching for #include "itkeigen/ patterns after reviewing the referenced commit.

[greptile-apps]

Greptile Summary

This PR updates the Eigen include path used by itkSpecialFunctions.h. The main changes are:

• Adds itk_eigen.h before the Eigen unsupported include.
• Replaces the hard-coded vendored Eigen path with ITK_EIGEN_UNSUPPORTED(SpecialFunctions).
• Keeps the existing special function calls routed through Eigen's unsupported header.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.
• The new macro include is defined before use.
• The Common module already depends on ITKEigen3.

Important Files Changed

Filename	Overview
Modules/Core/Common/include/itkSpecialFunctions.h	Switches the SpecialFunctions include to the configured Eigen include macro used for system and vendored Eigen builds.

_{Reviews (1): Last reviewed commit: "BUG: Replace hard-coded itkeigen/ path w..." | Re-trigger Greptile}

[blowekamp]

@greptile-apps Please remember include of Eigen headers need an ITK_EIGEN macro and direct include of eigen headers in ITK should not occur.

[greptile-apps]

Got it — I've created a rule to enforce this going forward.

Rule: All Eigen header includes in ITK must use the ITK_EIGEN macro family (e.g., ITK_EIGEN(...), ITK_EIGEN_UNSUPPORTED(...)). Direct hard-coded includes like #include "itkeigen/..." or #include <Eigen/...> are not permitted.

View rule