Remove check for zero template arguments, handle enable_if_t

Author: localspook

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

@@ -79,12 +79,8 @@ matchEnableIfSpecializationImplTypename(TypeLoc TheType) {
     if (!TD || TD->getName() != "enable_if")
       return std::nullopt;
 
-    const TemplateParameterList *Params = TD->getTemplateParameters();
-    if (Params->size() != 2)
-      return std::nullopt;
-
-    const auto *FirstParam =
-        dyn_cast<NonTypeTemplateParmDecl>(Params->getParam(0));
+    const auto *FirstParam = dyn_cast<NonTypeTemplateParmDecl>(
+        TD->getTemplateParameters()->getParam(0));
     if (!FirstParam || !FirstParam->getType()->isBooleanType())
       return std::nullopt;
 
@@ -118,6 +114,11 @@ matchEnableIfSpecializationImplTrait(TypeLoc TheType) {
     if (!Specialization->isTypeAlias())
       return std::nullopt;
 
+    const auto *FirstParam = dyn_cast<NonTypeTemplateParmDecl>(
+        TD->getTemplateParameters()->getParam(0));
+    if (!FirstParam || !FirstParam->getType()->isBooleanType())
+      return std::nullopt;
+
     if (const auto *AliasedType =
             dyn_cast<DependentNameType>(Specialization->getAliasedType())) {
       ElaboratedTypeKeyword Keyword = AliasedType->getKeyword();

clang-tools-extra/test/clang-tidy/checkers/modernize/use-constraints.cpp

@@ -768,20 +768,34 @@ namespace nonstd {
 template <bool Condition, typename T = void>
 struct enable_if : std::enable_if<Condition, T> {};
 
+template <bool Condition, typename T = void>
+using enable_if_t = typename enable_if<Condition, T>::type;
+
 }
 
 template <typename T>
 typename nonstd::enable_if<some_type_trait<T>::value, void>::type nonstd_enable_if() {}
 // CHECK-MESSAGES: :[[@LINE-1]]:1: warning: use C++20 requires constraints instead of enable_if [modernize-use-constraints]
 // CHECK-FIXES: {{^}}void nonstd_enable_if() requires some_type_trait<T>::value {}{{$}}
 
+template <typename T>
+nonstd::enable_if_t<some_type_trait<T>::value, void> nonstd_enable_if_t() {}
+// CHECK-MESSAGES: :[[@LINE-1]]:1: warning: use C++20 requires constraints instead of enable_if [modernize-use-constraints]
+// CHECK-FIXES: {{^}}void nonstd_enable_if_t() requires some_type_trait<T>::value {}{{$}}
+
 // But only if the non-standard enable_if has the same signature as the standard one.
 namespace boost {
 
 template <typename Condition, typename T = void>
 struct enable_if : std::enable_if<Condition::value, T> {};
 
+template <typename Condition, typename T = void>
+using enable_if_t = typename enable_if<Condition, T>::type;
+
 }
 
 template <typename T>
 typename boost::enable_if<some_type_trait<T>, void>::type boost_enable_if() {}
+
+template <typename T>
+boost::enable_if_t<some_type_trait<T>, void> boost_enable_if_t() {}