double lit(double x) {
  return 0.0;
}
->
double lit_darg0(double x) {
    double _d_x = 1;
    return 0;
}
FunctionDecl 0x5632986fe280 <<invalid sloc>> <invalid sloc> lit_darg0 'double (double)'
|-ParmVarDecl 0x5632986fe318 <<invalid sloc>> <invalid sloc> x 'double'
`-CompoundStmt 0x5632986fe4e8 <<invalid sloc>>
  |-DeclStmt 0x5632986fe418 <<invalid sloc>>
  | `-VarDecl 0x5632986fe3a0 <<invalid sloc>> <invalid sloc> used _d_x 'double' cinit
  |   `-ImplicitCastExpr 0x5632986fe400 <<invalid sloc>> 'double' <IntegralToFloating>
  |     `-IntegerLiteral 0x5632986fe380 <<invalid sloc>> 'int' 1
  `-ReturnStmt 0x5632986fe4b0 <<invalid sloc>>
    `-ImplicitCastExpr 0x5632986fe498 <<invalid sloc>> 'double' <IntegralToFloating>
      `-IntegerLiteral 0x5632986fe458 <<invalid sloc>> 'int' 0