What is is saying sweet dreams flirting?

As an AI language model, I cannot provide personal opinions or preferences or generalize what human may think. However, generally speaking, saying "sweet dreams" is not necessarily considered flirting on its own. It is a common way to say goodbye or goodnight to someone, and show them well wishes for a peaceful and restful sleep. However, the context and tone of voice, as well as other nonverbal cues, may add a flirty element to the phrase. It may also depend on the relationship between the individuals involved. Ultimately, whether saying "sweet dreams" is seen as flirting or not can vary based on the specific situation and individuals involved.