[lldb][DWARFASTParserClang] Make GetCXXObjectParameter public and call it from unit-tests (#144879)

My goal is to remove the `object_pointer` member on
`ParsedDWARFTypeAttributes` since it's duplicating information that we
retrieve with `GetCXXObjectParameter` anyway. To continue having
coverage for the `DW_AT_object_pointer` code-paths, instead of checking
the
`attrs.object_pointer` I'm now calling `GetCXXObjectParameter` directly.
We could find some very roundabout way to go via the Clang AST to check
that the object parameter was parsed correctly, but that quickly became
quite painful.

Depends on llvm/llvm-project#144876

Author: Michael137

lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp

@@ -163,8 +163,9 @@ static bool TagIsRecordType(dw_tag_t tag) {
 /// a default DWARFDIE. If \c containing_decl_ctx is not a valid
 /// C++ declaration context for class methods, assume no object
 /// parameter exists for the given \c subprogram.
-static DWARFDIE GetCXXObjectParameter(const DWARFDIE &subprogram,
-                                      const DWARFDIE &decl_ctx_die) {
+DWARFDIE
+DWARFASTParserClang::GetCXXObjectParameter(const DWARFDIE &subprogram,
+                                           const DWARFDIE &decl_ctx_die) {
   assert(subprogram);
   assert(subprogram.Tag() == DW_TAG_subprogram ||
          subprogram.Tag() == DW_TAG_inlined_subroutine ||

lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h

@@ -112,6 +112,10 @@ class DWARFASTParserClang : public lldb_private::plugin::dwarf::DWARFASTParser {
   void MapDeclDIEToDefDIE(const lldb_private::plugin::dwarf::DWARFDIE &decl_die,
                           const lldb_private::plugin::dwarf::DWARFDIE &def_die);
 
+  lldb_private::plugin::dwarf::DWARFDIE GetCXXObjectParameter(
+      const lldb_private::plugin::dwarf::DWARFDIE &subprogram,
+      const lldb_private::plugin::dwarf::DWARFDIE &decl_ctx_die);
+
 protected:
   /// Protected typedefs and members.
   /// @{

lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp

@@ -889,18 +889,32 @@ TEST_F(DWARFASTParserClangTests, TestParseDWARFAttributes_ObjectPointer) {
   ASSERT_TRUE(context_die.IsValid());
   ASSERT_EQ(context_die.Tag(), DW_TAG_structure_type);
 
-  auto subprogram_definition = context_die.GetSibling();
-  ASSERT_TRUE(subprogram_definition.IsValid());
-  ASSERT_EQ(subprogram_definition.Tag(), DW_TAG_subprogram);
-  ASSERT_FALSE(subprogram_definition.GetAttributeValueAsOptionalUnsigned(
-      DW_AT_external));
-
-  auto param_die = subprogram_definition.GetFirstChild();
-  ASSERT_TRUE(param_die.IsValid());
-
-  ParsedDWARFTypeAttributes attrs(subprogram_definition);
-  EXPECT_TRUE(attrs.object_pointer.IsValid());
-  EXPECT_EQ(attrs.object_pointer, param_die);
+  {
+    auto decl_die = context_die.GetFirstChild();
+    ASSERT_TRUE(decl_die.IsValid());
+    ASSERT_EQ(decl_die.Tag(), DW_TAG_subprogram);
+    ASSERT_TRUE(decl_die.GetAttributeValueAsOptionalUnsigned(DW_AT_external));
+
+    auto param_die = decl_die.GetFirstChild();
+    ASSERT_TRUE(param_die.IsValid());
+
+    EXPECT_EQ(param_die,
+              ast_parser.GetCXXObjectParameter(decl_die, context_die));
+  }
+
+  {
+    auto subprogram_definition = context_die.GetSibling();
+    ASSERT_TRUE(subprogram_definition.IsValid());
+    ASSERT_EQ(subprogram_definition.Tag(), DW_TAG_subprogram);
+    ASSERT_FALSE(subprogram_definition.GetAttributeValueAsOptionalUnsigned(
+        DW_AT_external));
+
+    auto param_die = subprogram_definition.GetFirstChild();
+    ASSERT_TRUE(param_die.IsValid());
+
+    EXPECT_EQ(param_die, ast_parser.GetCXXObjectParameter(subprogram_definition,
+                                                          context_die));
+  }
 }
 
 TEST_F(DWARFASTParserClangTests, TestParseSubroutine_ExplicitObjectParameter) {