How to fix defective AST with orphan node? - clang

Question

When Clang-Tidy scans test cases to generate AST. Orphan Node appears. Why AST is not completely generated, how to find the missing areas to repair test cases?
My command is
./bin/clang-tidy --checks=* /usr2/CodingProblemCases/format_string/01_format_var_count.cpp -- -DDEBUG -I/usr2/CodingProblemCases/build
Tried to match orphan node:
CXXRecordDecl 0x555555778758 <<invalid sloc>> <invalid sloc> implicit struct __va_list_tag definition
|-DefinitionData pass_in_registers aggregate standard_layout trivially_copyable pod trivial literal
| |-DefaultConstructor exists trivial
| |-CopyConstructor simple trivial has_const_param implicit_has_const_param
| |-MoveConstructor exists simple trivial
| |-CopyAssignment trivial has_const_param needs_implicit implicit_has_const_param
| |-MoveAssignment exists simple trivial needs_implicit
| `-Destructor simple irrelevant trivial
|-TypeVisibilityAttr 0x555555778810 <<invalid sloc>> Implicit Default
|-FieldDecl 0x5555557788b8 <<invalid sloc>> <invalid sloc> gp_offset 'unsigned int'
|-FieldDecl 0x555555778908 <<invalid sloc>> <invalid sloc> fp_offset 'unsigned int'
|-FieldDecl 0x555555778958 <<invalid sloc>> <invalid sloc> overflow_arg_area 'void *'
|-FieldDecl 0x555555a5b190 <<invalid sloc>> <invalid sloc> reg_save_area 'void *'
|-CXXConstructorDecl 0x555555c34ab8 <<invalid sloc>> <invalid sloc> implicit used __va_list_tag 'void () noexcept' inline default trivial
| `-CompoundStmt 0x555555c34ee8 <<invalid sloc>>
|-CXXConstructorDecl 0x555555c34bb8 <<invalid sloc>> <invalid sloc> implicit constexpr __va_list_tag 'void (const __va_list_tag &)' inline default trivial noexcept-unevaluated 0x555555c34bb8
| `-ParmVarDecl 0x555555c34cc8 <<invalid sloc>> <invalid sloc> 'const __va_list_tag &'
|-CXXConstructorDecl 0x555555c34d68 <<invalid sloc>> <invalid sloc> implicit constexpr __va_list_tag 'void (__va_list_tag &&)' inline default trivial noexcept-unevaluated 0x555555c34d68
| `-ParmVarDecl 0x555555c34e78 <<invalid sloc>> <invalid sloc> '__va_list_tag &&'
`-CXXDestructorDecl 0x555555c34f38 <<invalid sloc>> <invalid sloc> implicit referenced ~__va_list_tag 'void () noexcept' inline default trivial
Parent map should be complete!
UNREACHABLE executed at /clang/lib/ASTMatchers/ASTMatchFinder.cpp:694!