text: #include "as.h"
  
  noreturn void as_error(Location *loc, char *file, int lineno, char *format, ...) {
    va_list ap;
    va_start(ap, format);
    fprintf(stderr, "%s:%d:%d: error: ", loc->filename, loc->lineno, loc->column);
    vfprintf(stderr, format, ap);
    fprintf(stderr, " (at %s:%d)\n", file, lineno);
    va_end(ap);
  
    fprintf(stderr, " %s\n", loc->line);
    fprintf(stderr, "%*s^\n", loc->column, " ");
  
    exit(1);
  }
  