public void setWhileyDir(File dir) throws IOException {
// Note, we don't call super.setWhileyDir here as might be expected.
// This is because that would set the wyilDir to a matching directory
// root. However, for this builder, we don't want to write wyil files by
// default.
this.whileyDir = new DirectoryRoot(dir, whileyFileFilter, registry);
if (classDir == null) {
this.classDir = new DirectoryRoot(dir, classFileFilter,
registry);
}
}