Add isConstinit matcher

Support C++20 constinit variables for AST Matchers.

clang/docs/LibASTMatchersReference.html

@@ -5628,6 +5628,19 @@ ifStmt(isConstexpr())
 </pre></td></tr>
 
 
+<tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1VarDecl.html">VarDecl</a>&gt;</td><td class="name" onclick="toggle('isConstinit0')"><a name="isConstinit0Anchor">isConstinit</a></td><td></td></tr>
+<tr><td colspan="4" class="doc" id="isConstinit0"><pre>Matches constinit variable declarations.
+
+Given:
+  constinit int foo = 42;
+  constinit const char* bar = "baz";
+  int baz = 42;
+  [[clang::require_constant_initialization]] int xyz = 42;
+varDecl(isConstinit())
+  matches the declaration of `foo` and `bar`, but not `baz` and `xyz`.
+</pre></td></tr>
+
+
 <tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1VarDecl.html">VarDecl</a>&gt;</td><td class="name" onclick="toggle('isDefinition1')"><a name="isDefinition1Anchor">isDefinition</a></td><td></td></tr>
 <tr><td colspan="4" class="doc" id="isDefinition1"><pre>Matches if a declaration has a body attached.
 

clang/docs/ReleaseNotes.rst

@@ -331,6 +331,8 @@ AST Matchers
   underlying type.
 - Added the ``isConsteval`` matcher to match ``consteval`` function
   declarations as well as `if consteval` and `if ! consteval` statements.
+- Added the ``isConstinit`` matcher to match ``constinit`` variable
+  declarations.
 
 clang-format
 ------------

clang/include/clang/ASTMatchers/ASTMatchers.h

@@ -5211,6 +5211,23 @@ AST_POLYMORPHIC_MATCHER(isConstexpr,
   return Node.isConstexpr();
 }
 
+/// Matches constinit variable declarations.
+///
+/// Given:
+/// \code
+///   constinit int foo = 42;
+///   constinit const char* bar = "bar";
+///   int baz = 42;
+///   [[clang::require_constant_initialization]] int xyz = 42;
+/// \endcode
+/// varDecl(isConstinit())
+///   matches the declaration of `foo` and `bar`, but not `baz` and `xyz`.
+AST_MATCHER(VarDecl, isConstinit) {
+  if (const auto *CIA = Node.getAttr<ConstInitAttr>())
+    return CIA->isConstinit();
+  return false;
+}
+
 /// Matches selection statements with initializer.
 ///
 /// Given:

clang/lib/ASTMatchers/Dynamic/Registry.cpp

@@ -406,6 +406,7 @@ RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(isConstQualified);
   REGISTER_MATCHER(isConsteval);
   REGISTER_MATCHER(isConstexpr);
+  REGISTER_MATCHER(isConstinit);
   REGISTER_MATCHER(isCopyAssignmentOperator);
   REGISTER_MATCHER(isCopyConstructor);
   REGISTER_MATCHER(isDefaultConstructor);

clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

@@ -1841,6 +1841,25 @@ TEST_P(ASTMatchersTest, IsConstexpr_MatchesIfConstexpr) {
       notMatches("void baz() { if (1 > 0) {} }", ifStmt(isConstexpr())));
 }
 
+TEST_P(ASTMatchersTest, IsConstinit) {
+  if (!GetParam().isCXX20OrLater())
+    return;
+
+  EXPECT_TRUE(matches("constinit int foo = 1;",
+                      varDecl(hasName("foo"), isConstinit())));
+  EXPECT_TRUE(matches("extern constinit int foo;",
+                      varDecl(hasName("foo"), isConstinit())));
+  EXPECT_TRUE(matches("constinit const char* foo = \"bar\";",
+                      varDecl(hasName("foo"), isConstinit())));
+  EXPECT_TRUE(
+      notMatches("[[clang::require_constant_initialization]] int foo = 1;",
+                 varDecl(hasName("foo"), isConstinit())));
+  EXPECT_TRUE(notMatches("constexpr int foo = 1;",
+                         varDecl(hasName("foo"), isConstinit())));
+  EXPECT_TRUE(notMatches("static inline int foo = 1;",
+                         varDecl(hasName("foo"), isConstinit())));
+}
+
 TEST_P(ASTMatchersTest, HasInitStatement_MatchesSelectionInitializers) {
   EXPECT_TRUE(notMatches("void baz() { if (1 > 0) {} }",
                          ifStmt(hasInitStatement(anything()))));