[clang] [ASTMatchers] Use llvm::is_detected (NFC) (PR #137560)

[Kazu Hirata via cfe-commits]

https://github.com/kazutakahirata created https://github.com/llvm/llvm-project/pull/137560

None

>From 11261a022f2720eb3e368fd88981cb6b1c82c223 Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu at google.com>
Date: Sun, 27 Apr 2025 14:53:36 -0700
Subject: [PATCH] [ASTMatchers] Use llvm::is_detected (NFC)

---
 .../clang/ASTMatchers/ASTMatchersInternal.h    | 18 +++++-------------
 .../ASTMatchers/ASTMatchersTraversalTest.cpp   |  6 +++---
 2 files changed, 8 insertions(+), 16 deletions(-)

diff --git a/clang/include/clang/ASTMatchers/ASTMatchersInternal.h b/clang/include/clang/ASTMatchers/ASTMatchersInternal.h
index c1130ff70cf5c..8290645768aa9 100644
--- a/clang/include/clang/ASTMatchers/ASTMatchersInternal.h
+++ b/clang/include/clang/ASTMatchers/ASTMatchersInternal.h
@@ -881,20 +881,12 @@ inline bool isDefaultedHelper(const FunctionDecl *FD) {
 }
 
 // Metafunction to determine if type T has a member called getDecl.
-template <typename Ty>
-class has_getDecl {
-  using yes = char[1];
-  using no = char[2];
-
-  template <typename Inner>
-  static yes& test(Inner *I, decltype(I->getDecl()) * = nullptr);
-
-  template <typename>
-  static no& test(...);
+template <typename T>
+using check_has_getDecl = decltype(std::declval<T &>().getDecl());
 
-public:
-  static const bool value = sizeof(test<Ty>(nullptr)) == sizeof(yes);
-};
+template <typename T>
+static constexpr bool has_getDecl =
+    llvm::is_detected<check_has_getDecl, T>::value;
 
 /// Matches overloaded operators with a specific name.
 ///
diff --git a/clang/unittests/ASTMatchers/ASTMatchersTraversalTest.cpp b/clang/unittests/ASTMatchers/ASTMatchersTraversalTest.cpp
index 74844167d5e5a..8759811092b6f 100644
--- a/clang/unittests/ASTMatchers/ASTMatchersTraversalTest.cpp
+++ b/clang/unittests/ASTMatchers/ASTMatchersTraversalTest.cpp
@@ -226,11 +226,11 @@ TEST(HasDeclaration, HasDeclarationOfEnumType) {
 }
 
 TEST(HasDeclaration, HasGetDeclTraitTest) {
-  static_assert(internal::has_getDecl<TypedefType>::value,
+  static_assert(internal::has_getDecl<TypedefType>,
                 "Expected TypedefType to have a getDecl.");
-  static_assert(internal::has_getDecl<RecordType>::value,
+  static_assert(internal::has_getDecl<RecordType>,
                 "Expected RecordType to have a getDecl.");
-  static_assert(!internal::has_getDecl<TemplateSpecializationType>::value,
+  static_assert(!internal::has_getDecl<TemplateSpecializationType>,
                 "Expected TemplateSpecializationType to *not* have a getDecl.");
 }