Function copy_symbol_value 

pub fn copy_symbol_value(
    symbol: &str,
    source: &SymbolTable,
    dest: &mut SymbolTable,
)

Walk a dotted symbol name into source, find the deepest Value entry, and copy it into dest at the same path.

E.g. for “Param.Name.upper”, if source has Param.Name = “hello” (a Value), we copy Param.Name into dest. The “.upper” part is a method call, not a symtab key.