return &ModuleError{Path: path, Err: err}
	}
	return nil
}

// firstPathOK reports whether r can appear in the first element of a module path.
// The first element of the path must be an LDH domain name, at least for now.
// To avoid case ambiguity, the domain name must be entirely lower case.
func firstPathOK(r rune) bool {
	return r == '-' || r == '.' ||
		'0' <= r && r <= '9' ||
		'a' <= r && r <= 'z'
}