Revert "Detect against invalid variant index for LibStdC++ std::variant data formatters (llvm#69253)"

This reverts commit 659a48f.

This caused another test to fail on Windows AArch64 and x86_64, and AArch64 Linux.

Author: DavidSpickett

lldb/examples/synthetic/gnu_libstdcpp.py

@@ -914,11 +914,6 @@ def get_variant_npos_value(index_byte_size):
     if index == npos_value:
         return " No Value"
 
-    # Invalid index can happen when the variant is not initialized yet.
-    template_arg_count = data_obj.GetType().GetNumberOfTemplateArguments()
-    if index >= template_arg_count:
-        return " <Invalid>"
-
     active_type = data_obj.GetType().GetTemplateArgumentType(index)
     return f" Active Type = {active_type.GetDisplayTypeName()} "
 

lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp

@@ -7182,9 +7182,6 @@ GetNthTemplateArgument(const clang::ClassTemplateSpecializationDecl *decl,
   // Note that 'idx' counts from the beginning of all template arguments
   // (including the ones preceding the parameter pack).
   const auto &pack = args[last_idx];
-  if (idx >= pack.pack_size())
-    return nullptr;
-
   const size_t pack_idx = idx - last_idx;
   assert(pack_idx < pack.pack_size() && "parameter pack index out-of-bounds");
   return &pack.pack_elements()[pack_idx];

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/variant/TestDataFormatterLibStdcxxVariant.py

@@ -71,29 +71,3 @@ def test_with_run_command(self):
             substrs=["v_many_types_no_value =  No Value"],
         )
         """
-
-    @add_test_categories(["libstdcxx"])
-    def test_invalid_variant_index(self):
-        """Test LibStdC++ data formatter for std::variant with invalid index."""
-        self.build()
-
-        (self.target, self.process, thread, bkpt) = lldbutil.run_to_source_breakpoint(
-            self, "// break here", lldb.SBFileSpec("main.cpp", False)
-        )
-
-        lldbutil.continue_to_breakpoint(self.process, bkpt)
-
-        self.expect(
-            "frame variable v1",
-            substrs=["v1 =  Active Type = int  {", "Value = 12", "}"],
-        )
-
-        var_v1 = thread.frames[0].FindVariable("v1")
-        var_v1_raw_obj = var_v1.GetNonSyntheticValue()
-        index_obj = var_v1_raw_obj.GetChildMemberWithName("_M_index")
-        self.assertTrue(index_obj and index_obj.IsValid())
-
-        INVALID_INDEX = "100"
-        index_obj.SetValueFromCString(INVALID_INDEX)
-
-        self.expect("frame variable v1", substrs=["v1 =  <Invalid>"])