[cindex] Add API to query the class methods of a type (#123539)

Inspired by https://github.com/llvm/llvm-project/pull/120300, add a new
API `clang_visitCXXMethods` to libclang (and the Python bindings) which
allows iterating over the class methods of a type.

---------

Co-authored-by: Vlad Serebrennikov <serebrennikov.vladislav@gmail.com>
Co-authored-by: Aaron Ballman <aaron@aaronballman.com>

clang/bindings/python/clang/cindex.py

@@ -2713,6 +2713,21 @@ class Type(Structure):
         conf.lib.clang_visitCXXBaseClasses(self, fields_visit_callback(visitor), bases)
         return iter(bases)
 
+    def get_methods(self):
+        """Return an iterator for accessing the methods of this type."""
+
+        def visitor(method, children):
+            assert method != conf.lib.clang_getNullCursor()
+
+            # Create reference to TU so it isn't GC'd before Cursor.
+            method._tu = self._tu
+            methods.append(method)
+            return 1  # continue
+
+        methods: list[Cursor] = []
+        conf.lib.clang_visitCXXMethods(self, fields_visit_callback(visitor), methods)
+        return iter(methods)
+
     def get_exception_specification_kind(self):
         """
         Return the kind of the exception specification; a value from
@@ -4020,6 +4035,7 @@ functionList: list[LibFunc] = [
     ),
     ("clang_visitChildren", [Cursor, cursor_visit_callback, py_object], c_uint),
     ("clang_visitCXXBaseClasses", [Type, fields_visit_callback, py_object], c_uint),
+    ("clang_visitCXXMethods", [Type, fields_visit_callback, py_object], c_uint),
     ("clang_Cursor_getNumArguments", [Cursor], c_int),
     ("clang_Cursor_getArgument", [Cursor, c_uint], Cursor),
     ("clang_Cursor_getNumTemplateArguments", [Cursor], c_int),

clang/bindings/python/tests/cindex/test_type.py

@@ -559,3 +559,21 @@ class A
         self.assertEqual(bases[1].get_base_offsetof(cursor_type_decl), 96)
         self.assertTrue(bases[2].is_virtual_base())
         self.assertEqual(bases[2].get_base_offsetof(cursor_type_decl), 128)
+
+    def test_class_methods(self):
+        source = """
+        template <typename T>
+        class Template { void Foo(); };
+        typedef Template<int> instance;
+        instance bar;
+        """
+        tu = get_tu(source, lang="cpp", flags=["--target=x86_64-linux-gnu"])
+        cursor = get_cursor(tu, "instance")
+        cursor_type = cursor.underlying_typedef_type
+        self.assertEqual(cursor.kind, CursorKind.TYPEDEF_DECL)
+        methods = list(cursor_type.get_methods())
+        self.assertEqual(len(methods), 4)
+        self.assertEqual(methods[0].kind, CursorKind.CXX_METHOD)
+        self.assertEqual(methods[1].kind, CursorKind.CONSTRUCTOR)
+        self.assertEqual(methods[2].kind, CursorKind.CONSTRUCTOR)
+        self.assertEqual(methods[3].kind, CursorKind.CONSTRUCTOR)

clang/docs/ReleaseNotes.rst

@@ -349,6 +349,8 @@ clang-format
 
 libclang
 --------
+- Added ``clang_visitCXXMethods``, which allows visiting the methods
+  of a class.
 
 - Fixed a buffer overflow in ``CXString`` implementation. The fix may result in
   increased memory allocation.
@@ -388,6 +390,8 @@ Sanitizers
 
 Python Binding Changes
 ----------------------
+- Added ``Type.get_methods``, a binding for ``clang_visitCXXMethods``, which
+  allows visiting the methods of a class.
 
 OpenMP Support
 --------------

clang/include/clang-c/Index.h

@@ -6628,6 +6628,28 @@ CINDEX_LINKAGE unsigned clang_visitCXXBaseClasses(CXType T,
                                                   CXFieldVisitor visitor,
                                                   CXClientData client_data);
 
+/**
+ * Visit the class methods of a type.
+ *
+ * This function visits all the methods of the given cursor,
+ * invoking the given \p visitor function with the cursors of each
+ * visited method. The traversal may be ended prematurely, if
+ * the visitor returns \c CXFieldVisit_Break.
+ *
+ * \param T The record type whose field may be visited.
+ *
+ * \param visitor The visitor function that will be invoked for each
+ * field of \p T.
+ *
+ * \param client_data Pointer data supplied by the client, which will
+ * be passed to the visitor each time it is invoked.
+ *
+ * \returns A non-zero value if the traversal was terminated
+ * prematurely by the visitor returning \c CXFieldVisit_Break.
+ */
+CINDEX_LINKAGE unsigned clang_visitCXXMethods(CXType T, CXFieldVisitor visitor,
+                                              CXClientData client_data);
+
 /**
  * Describes the kind of binary operators.
  */

clang/tools/libclang/CIndexCXX.cpp

@@ -54,6 +54,32 @@ unsigned clang_visitCXXBaseClasses(CXType PT, CXFieldVisitor visitor,
   return true;
 }
 
+unsigned clang_visitCXXMethods(CXType PT, CXFieldVisitor visitor,
+                               CXClientData client_data) {
+  CXCursor PC = clang_getTypeDeclaration(PT);
+  if (clang_isInvalid(PC.kind))
+    return false;
+  const auto *RD =
+      dyn_cast_if_present<CXXRecordDecl>(cxcursor::getCursorDecl(PC));
+  if (!RD || RD->isInvalidDecl())
+    return false;
+  RD = RD->getDefinition();
+  if (!RD || RD->isInvalidDecl())
+    return false;
+
+  for (const auto *Method : RD->methods()) {
+    // Callback to the client.
+    switch (
+        visitor(cxcursor::MakeCXCursor(Method, getCursorTU(PC)), client_data)) {
+    case CXVisit_Break:
+      return true;
+    case CXVisit_Continue:
+      break;
+    }
+  }
+  return true;
+}
+
 enum CX_CXXAccessSpecifier clang_getCXXAccessSpecifier(CXCursor C) {
   AccessSpecifier spec = AS_none;
 

clang/tools/libclang/libclang.map

@@ -435,6 +435,7 @@ LLVM_20 {
     clang_getTypePrettyPrinted;
     clang_isBeforeInTranslationUnit;
     clang_visitCXXBaseClasses;
+    clang_visitCXXMethods;
 };
 
 # Example of how to add a new symbol version entry.  If you do add a new symbol