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[clang-tidy] Limit modernize-use-constraints to standard enable_if #155237

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[clang-tidy] Limit modernize-use-constraints to standard enable_if #155237

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4 changes: 2 additions & 2 deletions clang-tools-extra/clang-tidy/modernize/UseConstraintsCheck.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,7 @@ matchEnableIfSpecializationImplTypename(TypeLoc TheType) {

const TemplateDecl *TD =
Specialization->getTemplateName().getAsTemplateDecl();
if (!TD || TD->getName() != "enable_if")
if (!TD || TD->getName() != "enable_if" || !TD->isInStdNamespace())
return std::nullopt;

int NumArgs = SpecializationLoc.getNumArgs();
Expand All @@ -101,7 +101,7 @@ matchEnableIfSpecializationImplTrait(TypeLoc TheType) {

const TemplateDecl *TD =
Specialization->getTemplateName().getAsTemplateDecl();
if (!TD || TD->getName() != "enable_if_t")
if (!TD || TD->getName() != "enable_if_t" || !TD->isInStdNamespace())
return std::nullopt;

if (!Specialization->isTypeAlias())
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30 changes: 30 additions & 0 deletions clang-tools-extra/test/clang-tidy/checkers/modernize/use-constraints.cpp
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Expand Up @@ -756,3 +756,33 @@ abs(const number<T, ExpressionTemplates> &v) {
}

}

// NOLINTBEGIN
namespace custom {
template <bool B, class T = void> struct enable_if { };

template <class T> struct enable_if<true, T> { typedef T type; };

template <bool B, class T = void>
using enable_if_t = typename enable_if<B, T>::type;

} // namespace custom
// NOLINTEND
Comment on lines +760 to +770
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Except for the name of the namespace, this block is identical to the namespace std block at the beginning of this test file. I don't understand the purpose of the NOLINTBEGIN/NOLINTEND markers, so I just copied them blindly. Feel free to suggest removing them if you know that they are superfluous (in that case I'll probably remove them from the beginning of the file as well).


namespace use_custom {
// We cannot assume anything about the behavior of templates that happen to be
// named `enable_if` or `enable_if_t` if they are not declared in the namespace
// `std`. (E.g. the first template parameter of `boost::enable_if` is a class
// and not a boolean and `boost::enable_if<Cond, T>` is equivalent to
// `std::enable_if<Cond::value, T>`.)

template <typename T>
typename custom::enable_if<T::some_value, Obj>::type custom_basic() {
return Obj{};
}

template <typename T>
custom::enable_if_t<T::some_value, Obj> custom_basic_t() {
return Obj{};
}
}