[clang-tidy] Teach `modernize-type-traits` about more type traits #147074

localspook · 2025-07-04T14:57:31Z

These new traits come from various standard versions:

C++14:

tuple_element_t

C++17:

is_placeholder_v
is_bind_expression_v
ratio_equal_v
ratio_not_equal_v
ratio_less_v
ratio_less_equal_v
ratio_greater_v
ratio_greater_equal_v
is_error_code_enum_v
is_error_condition_enum_v
is_execution_policy_v
tuple_size_v
variant_size_v
uses_allocator_v
variant_alternative_t

C++20:

compare_three_way_result_t
common_comparison_category_t
unwrap_ref_decay_t
unwrap_reference_t

C++23:

is_implicit_lifetime_v

C++26:

is_nothrow_relocatable_v
is_replaceable_v
is_trivially_relocatable_v
is_virtual_base_of_v

This doesn't add treat_as_floating_point_v or is_clock_v because they require more invasive changes; instead I've opened #147072 to track them.

github-actions · 2025-07-04T14:57:47Z

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llvmbot · 2025-07-04T14:58:13Z

@llvm/pr-subscribers-clang-tools-extra

Author: Victor Chernyakin (localspook)

Changes

These new traits come from various standard versions:

C++14:

tuple_element_t

C++17:

is_placeholder_v
is_bind_expression_v
ratio_equal_v
ratio_not_equal_v
ratio_less_v
ratio_less_equal_v
ratio_greater_v
ratio_greater_equal_v
is_error_code_enum_v
is_error_condition_enum_v
is_execution_policy_v
tuple_size_v
variant_size_v
uses_allocator_v
variant_alternative_t

C++20:

compare_three_way_result_t
common_comparison_category_t
unwrap_ref_decay_t
unwrap_reference_t

C++23:

is_implicit_lifetime_v

C++26:

is_nothrow_relocatable_v
is_replaceable_v
is_trivially_relocatable_v
is_virtual_base_of_v

This doesn't add treat_as_floating_point_v or is_clock_v because they require more invasive changes; instead I've opened #147072 to track them.

Full diff: https://github.com/llvm/llvm-project/pull/147074.diff

2 Files Affected:

(modified) clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp (+27)
(modified) clang-tools-extra/docs/ReleaseNotes.rst (+3)

diff --git a/clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp b/clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp
index c0766395ec5cc..92e6f61a6d9d4 100644
--- a/clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp
@@ -28,8 +28,10 @@ static const llvm::StringSet<> ValueTraits = {
     "is_array",
     "is_assignable",
     "is_base_of",
+    "is_bind_expression",
     "is_bounded_array",
     "is_class",
+    "is_clock",
     "is_compound",
     "is_const",
     "is_constructible",
@@ -40,10 +42,14 @@ static const llvm::StringSet<> ValueTraits = {
     "is_destructible",
     "is_empty",
     "is_enum",
+    "is_error_code_enum",
+    "is_error_condition_enum",
+    "is_execution_policy",
     "is_final",
     "is_floating_point",
     "is_function",
     "is_fundamental",
+    "is_implicit_lifetime",
     "is_integral",
     "is_invocable",
     "is_invocable_r",
@@ -65,14 +71,17 @@ static const llvm::StringSet<> ValueTraits = {
     "is_nothrow_invocable_r",
     "is_nothrow_move_assignable",
     "is_nothrow_move_constructible",
+    "is_nothrow_relocatable",
     "is_nothrow_swappable",
     "is_nothrow_swappable_with",
     "is_null_pointer",
     "is_object",
+    "is_placeholder",
     "is_pointer",
     "is_pointer_interconvertible_base_of",
     "is_polymorphic",
     "is_reference",
+    "is_replaceable",
     "is_rvalue_reference",
     "is_same",
     "is_scalar",
@@ -91,15 +100,27 @@ static const llvm::StringSet<> ValueTraits = {
     "is_trivially_destructible",
     "is_trivially_move_assignable",
     "is_trivially_move_constructible",
+    "is_trivially_relocatable",
     "is_unbounded_array",
     "is_union",
     "is_unsigned",
+    "is_virtual_base_of",
     "is_void",
     "is_volatile",
     "negation",
     "rank",
+    "ratio_equal",
+    "ratio_greater_equal",
+    "ratio_greater",
+    "ratio_less_equal",
+    "ratio_less",
+    "ratio_not_equal",
     "reference_constructs_from_temporary",
     "reference_converts_from_temporary",
+    "treat_as_floating_point",
+    "tuple_size",
+    "uses_allocator",
+    "variant_size",
 };
 
 static const llvm::StringSet<> TypeTraits = {
@@ -130,6 +151,12 @@ static const llvm::StringSet<> TypeTraits = {
     "result_of",
     "invoke_result",
     "type_identity",
+	"tuple_element",
+	"variant_alternative",
+	"compare_three_way_result",
+	"common_comparison_category",
+	"unwrap_ref_decay",
+	"unwrap_reference",
 };
 
 static DeclarationName getName(const DependentScopeDeclRefExpr &D) {
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index f8f183e9de1cc..3d554733ad3fd 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -276,6 +276,9 @@ Changes in existing checks
   excluding variables with ``thread_local`` storage class specifier from being
   matched.
 
+- Improved :doc:`modernize-type-traits
+  <clang-tidy/checks/modernize/type-traits>` check by detecting more type traits.
+
 - Improved :doc:`modernize-use-default-member-init
   <clang-tidy/checks/modernize/use-default-member-init>` check by matching
   arithmetic operations, ``constexpr`` and ``static`` values, and detecting

llvmbot · 2025-07-04T14:58:14Z

@llvm/pr-subscribers-clang-tidy

Author: Victor Chernyakin (localspook)

Changes

These new traits come from various standard versions:

C++14:

tuple_element_t

C++17:

is_placeholder_v
is_bind_expression_v
ratio_equal_v
ratio_not_equal_v
ratio_less_v
ratio_less_equal_v
ratio_greater_v
ratio_greater_equal_v
is_error_code_enum_v
is_error_condition_enum_v
is_execution_policy_v
tuple_size_v
variant_size_v
uses_allocator_v
variant_alternative_t

C++20:

compare_three_way_result_t
common_comparison_category_t
unwrap_ref_decay_t
unwrap_reference_t

C++23:

is_implicit_lifetime_v

C++26:

is_nothrow_relocatable_v
is_replaceable_v
is_trivially_relocatable_v
is_virtual_base_of_v

This doesn't add treat_as_floating_point_v or is_clock_v because they require more invasive changes; instead I've opened #147072 to track them.

Full diff: https://github.com/llvm/llvm-project/pull/147074.diff

2 Files Affected:

(modified) clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp (+27)
(modified) clang-tools-extra/docs/ReleaseNotes.rst (+3)

diff --git a/clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp b/clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp
index c0766395ec5cc..92e6f61a6d9d4 100644
--- a/clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp
@@ -28,8 +28,10 @@ static const llvm::StringSet<> ValueTraits = {
     "is_array",
     "is_assignable",
     "is_base_of",
+    "is_bind_expression",
     "is_bounded_array",
     "is_class",
+    "is_clock",
     "is_compound",
     "is_const",
     "is_constructible",
@@ -40,10 +42,14 @@ static const llvm::StringSet<> ValueTraits = {
     "is_destructible",
     "is_empty",
     "is_enum",
+    "is_error_code_enum",
+    "is_error_condition_enum",
+    "is_execution_policy",
     "is_final",
     "is_floating_point",
     "is_function",
     "is_fundamental",
+    "is_implicit_lifetime",
     "is_integral",
     "is_invocable",
     "is_invocable_r",
@@ -65,14 +71,17 @@ static const llvm::StringSet<> ValueTraits = {
     "is_nothrow_invocable_r",
     "is_nothrow_move_assignable",
     "is_nothrow_move_constructible",
+    "is_nothrow_relocatable",
     "is_nothrow_swappable",
     "is_nothrow_swappable_with",
     "is_null_pointer",
     "is_object",
+    "is_placeholder",
     "is_pointer",
     "is_pointer_interconvertible_base_of",
     "is_polymorphic",
     "is_reference",
+    "is_replaceable",
     "is_rvalue_reference",
     "is_same",
     "is_scalar",
@@ -91,15 +100,27 @@ static const llvm::StringSet<> ValueTraits = {
     "is_trivially_destructible",
     "is_trivially_move_assignable",
     "is_trivially_move_constructible",
+    "is_trivially_relocatable",
     "is_unbounded_array",
     "is_union",
     "is_unsigned",
+    "is_virtual_base_of",
     "is_void",
     "is_volatile",
     "negation",
     "rank",
+    "ratio_equal",
+    "ratio_greater_equal",
+    "ratio_greater",
+    "ratio_less_equal",
+    "ratio_less",
+    "ratio_not_equal",
     "reference_constructs_from_temporary",
     "reference_converts_from_temporary",
+    "treat_as_floating_point",
+    "tuple_size",
+    "uses_allocator",
+    "variant_size",
 };
 
 static const llvm::StringSet<> TypeTraits = {
@@ -130,6 +151,12 @@ static const llvm::StringSet<> TypeTraits = {
     "result_of",
     "invoke_result",
     "type_identity",
+	"tuple_element",
+	"variant_alternative",
+	"compare_three_way_result",
+	"common_comparison_category",
+	"unwrap_ref_decay",
+	"unwrap_reference",
 };
 
 static DeclarationName getName(const DependentScopeDeclRefExpr &D) {
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index f8f183e9de1cc..3d554733ad3fd 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -276,6 +276,9 @@ Changes in existing checks
   excluding variables with ``thread_local`` storage class specifier from being
   matched.
 
+- Improved :doc:`modernize-type-traits
+  <clang-tidy/checks/modernize/type-traits>` check by detecting more type traits.
+
 - Improved :doc:`modernize-use-default-member-init
   <clang-tidy/checks/modernize/use-default-member-init>` check by matching
   arithmetic operations, ``constexpr`` and ``static`` values, and detecting

Copilot

Pull Request Overview

Adds support for more C++ type traits in the modernize-type-traits clang-tidy check and updates the release notes accordingly.

Expanded ValueTraits and TypeTraits string sets in TypeTraitsCheck.cpp with new traits from C++14 through C++26.
Updated ReleaseNotes.rst to document enhanced detection in the modernize-type-traits check.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
clang-tools-extra/docs/ReleaseNotes.rst	Added a bullet to announce improved trait detection in the modernize-type-traits check
clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp	Inserted numerous new trait names into `ValueTraits` and `TypeTraits` sets

Comments suppressed due to low confidence (2)

clang-tools-extra/docs/ReleaseNotes.rst:279

[nitpick] The bullet link is split across two lines which may break RST formatting; consider combining the link and description on one line or properly indenting the continuation to match list formatting.

- Improved :doc:`modernize-type-traits

clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp:152

This line uses a tab for indentation; please replace it with spaces to match the surrounding entries and project style.

	"tuple_element",

clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp

vbvictor

Thank you for the patch!
Could you please add tests with new traits from C++20, 23, 26 standards to make sure we get warning for newer standards than C++17. You will need to change -std=c++17 to -std=c++17-or-later in tests.

clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp

vbvictor · 2025-07-04T16:13:47Z

I wonder did you find this somehow automatically or manually?

localspook · 2025-07-04T17:00:31Z

Mostly manually: I took a list of all standard library symbols, used a hacky regex to find foo/foo_[tv] pairs, filtered out the false positives, diffed against the check's current list, and added what was missing.

localspook · 2025-07-04T18:10:39Z

I've changed the tests to use -std=c++17-or-later, but I don't think we need to add tests for the new traits because that wouldn't exercise any new codepaths. It's not like we only match on compare_three_way_result if compiling in C++20, no, we match on all traits in all modes.

clang-tools-extra/docs/clang-tidy/checks/modernize/type-traits.rst

clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp

vbvictor

LGTM, we'd wait a couple of days before merge in case someone else wants to review it too.

localspook · 2025-07-06T16:13:13Z

When we're ready to merge, someone please do it for me, I don't have write permissions.

[clang-tidy] Teach modernize-type-traits about more type traits

7ad6f7b

llvmbot added clang-tools-extra clang-tidy labels Jul 4, 2025

Whoops, didn't exclude treat_as_floating_point_v or is_clock_v

930db52

EugeneZelenko requested review from PiotrZSL, Copilot, vbvictor, carlosgalvezp, 5chmidti and HerrCai0907 July 4, 2025 15:07

Copilot AI reviewed Jul 4, 2025

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clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp Outdated Show resolved Hide resolved

clang-format

13dcaab

vbvictor requested changes Jul 4, 2025

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clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp Outdated Show resolved Hide resolved

Test new standards, exclude tuple_element_t

52df969

Exclude variant_alternative_t, document limitations

522e996

vbvictor requested changes Jul 4, 2025

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clang-tools-extra/docs/clang-tidy/checks/modernize/type-traits.rst Outdated Show resolved Hide resolved

clang-tools-extra/clang-tidy/modernize/TypeTraitsCheck.cpp Show resolved Hide resolved

Add variadic traits back

839f01e

vbvictor approved these changes Jul 6, 2025

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[clang-tidy] Teach `modernize-type-traits` about more type traits #147074

[clang-tidy] Teach `modernize-type-traits` about more type traits #147074

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[clang-tidy] Teach `modernize-type-traits` about more type traits #147074

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