[dzenanz]

Reimplement itk::Concept as std::bool_constant traits checked by static_assert, enable concept checks that the removed ITK_USE_CONCEPT_CHECKING had silently disabled, and use plain static_assert where no concept is needed.

Commits

1. ENH: Implement itk::Concept checks as static_assert of type traits: itkConceptChecking.h goes from 981 to 277 lines. Concepts use standard type traits or the detection idiom, and itkConceptMacro is a static_assert whose message names the check and the concept.
2. ENH: Enable concept checks guarded by removed ITK_USE_CONCEPT_CHECKING: about 50 checks in 18 ingested remote modules never compiled. This commit enables them and fixes MovingImageDimension in PhaseCorrelationImageRegistrationMethod, which was derived from the fixed image type.
3. STYLE: Replace dimension and type concept checks with static_assert: 162 checks become concept-free expressions or standard traits, such as ImageDimension == OutputImageDimension and std::is_same_v. The remaining 757 uses keep itkConceptMacro.
4. STYLE: Remove "Begin/End concept checking" comments

Behavior changes

• HasNumericTraits rejects types that have only the primary NumericTraits template. It caught itkNumericTraitsTest asserting HasNumericTraits<std::vector<float>> without including itkNumericTraitsStdVector.h; that specialization lacks IsPositive and the related functions, so the assertion is removed.
• Other checks look only at declarations (SFINAE), not at function bodies.
• Removed: ITK_CONCEPT_NO_CHECKING and the itkConceptConstraintsMacro and Concept::Detail helpers for custom concepts. The only external user found is dmritool's utlITKConceptChecking.h.

Local testing (macOS arm64, Apple clang 21)

• C++ build of the default modules plus the 18 ingested modules: no errors.
• Python wrapping build with the nightly MacOS-Rel-Python dashboard configuration (ITK_LEGACY_REMOVE=ON, ITKReview, Montage, RLEImage, …) plus the ingested modules: 3 failures, all in IsotropicWavelets' itk::Matrix<std::complex<T>> and VariableSizeMatrix<std::complex<T>> wrappers. GetInverse reaches itkBridgeMathSVD.h and itkBridgeEigenDecompositionSignConvention.h, which compare complex values with < and >. This reproduces on unmodified upstream/main, and this PR touches neither file.
• ctest: 6590 of 6623 pass, including all C++ tests. Of the 33 Python failures, 32 come from _IsotropicWaveletsPython not building (see above). The other is PythonMedianImageFilterTest, a Python 3.15 typing error in get_type_hints.
• Every concept was checked with pass and fail cases under Apple clang and GCC 16, in C++17 and C++20.

AI assistance

• Tool: Claude Code
• Role: designed the trait-based header, wrote the conversion scripts for commits 2–4, and ran the local builds and tests above.
• The author reviewed the commits.

🤖 Generated with Claude Code

[hjmjohnson]

AWESOME!!!

[dzenanz]

Thank you for improving this change Niels!

[greptile-apps]

Confidence Score: 4/5

[Medium impact] The PR changes compile-time type checks across many ITK modules.

Fix the complex-image build failure and remove the unused include to meet the project standard before merging.

Findings

1.  Complex images stop compiling ▶
2.  Pixel trait queries fail ▶
3.  False results lack tests ▶
4.  Unused include violates project standards ▶

Summary

Replaces itk::Concept checks with boolean traits and static_assert, enables dormant checks, and corrects the moving-image dimension in Montage.

• ITK templates check their type requirements at compile time.

_{Reviews (1) · Last reviewed commit: "STYLE: Remove "Begin/End concept checkin..." · Reviewed by Greptile}

[greptile-apps]

Complex images stop compiling

MaximumAbsoluteValueImageFilter<Image<std::complex<float>, 3>> now fails to compile because this enabled check requires > and >= on complex pixels. The filter compares their magnitudes through Math::Absolute, which returns a floating-point value, then returns the selected complex pixel. Check the magnitude types instead, or remove the raw-pixel ordering check.

Suggested change

itkConceptMacro(Input1GreaterThanInput2Check, (Concept::GreaterThanComparable<Input1PixelType, Input2PixelType>));

[greptile-apps]

Pixel trait queries fail

HasPixelTraits<std::complex<double>>::value produces a compile error instead of false. Looking up PixelTraits<T>::ValueType creates the primary PixelTraits class, whose own TPixelType::ValueType declaration fails outside the scope that IsValidExpression can catch. Callers therefore cannot use this boolean trait in if constexpr to choose a fallback. Make the primary PixelTraits safe to probe and add a false-case test.

[greptile-apps]

False results lack tests

The rewritten traits have no committed tests for false results. The remaining checks in itkNumericTraitsTest.cxx all require success, and the invalid std::vector<float> check is deleted rather than changed to assert false. Commit the local pass/fail cases as positive and negative static_assert tests, including rejected HasNumericTraits and Convertible cases. Otherwise CI cannot catch a check that silently starts accepting invalid types.

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

[greptile-apps]

Unused include violates project standards

The added <utility> include has no user. Lvalue replaces std::declval, and nothing else here uses that header. The project standard says “Include only what you use.” Remove the include before merging to satisfy that requirement.

Suggested change

#include <utility>

Context Used: AGENTS.md (source)

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!