Is rust-analyzer shows info or tryies complete the line?

resim
What thif gray boxes mean? ("fn sin" and ": f32")

That's extra info from rust-analyzer. It shows that angle has the type f32.

The gray box containing fn sin show that the sin function ends there. All the gray boxes are called inlay hints. You can enable and disable specific kinds of them using the rust-analyzer.inlayHints.* family of configuration options.