Pun rhetoric is used here. "Sunny" refers to both sunny weather and emotional "mood". It shows the hero's beautiful and pure love. The author (that is, Liu Yuxi) describes the confusion and sweetness in confusing love with a woman's tone and mentality, which is full of rich and fragrant local flavor.
The original poem is: ("Zhi Zhu Ci" Yuxi, Liu Tang)
The willow-green river is wide and flat, and I heard the song of the river.
Rain in the east, sunrise in the east, said it was not sunny, but it was still sunny.
In spring, willow trees with blue hanging strips hang neatly on the river, stretching endlessly. Although I can't see the lover to whom my heart belongs, I can hear his loud singing faintly fluttering. At this time, the weather appeared the scene of sunrise in the east and rain in the west. This unpredictable and elusive situation is like the feelings between my lover and me.