The following input:

auto X = __builtin_LINE();

generates following output:

unsigned int X = /* INSIGHTS-TODO: CodeGenerator.cpp:3851 stmt: SourceLocExpr */;

According to https://docs.hdoc.io/hdoc/llvm-project/r728584FDD0102CEF.html the class SourceLocExpr represents a function call to one of __builtin_LINE(), __builtin_COLUMN(), __builtin_FUNCTION(), __builtin_FILE(), or __builtin_source_location().
Especially with the C++20 std::source_location it would be neat if cppinsights would support this.

Best regards!