// 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'
}

// modPathOK reports whether r can appear in a module path element.
// Paths can be ASCII letters, ASCII digits, and limited ASCII punctuation: - . _ and ~.
//
// This matches what "go get" has historically recognized in import paths,

	}

	return pkg, sym, nil
}

// Borrowed from x/mod.
func modPathOK(r rune) bool {
	if r < utf8.RuneSelf {
		return r == '-' || r == '.' || r == '_' || r == '~' ||
			'0' <= r && r <= '9' ||
			'A' <= r && r <= 'Z' ||
			'a' <= r && r <= 'z'
	}
	return false
}

func escapedImportPathOK(r rune) bool {
	return modPathOK(r) || r == '+' || r == '/' || r == '%'
}