It looks like this is blocked upstream by the language server protocol not passing the current selection for hover requests [0].

0: https://github.com/microsoft/language-server-protocol/issues...

FWIW, this should be relatively easy to implement. Looking at all the pieces which implement https://github.com/rust-analyzer/rust-analyzer/blob/master/d... should given enough knowledge to do this.

At least in Emacs, it shows the type as a tooltip if I hover over the closing paren of a function call.

With inline hints you can get something somewhat similar, although they can get very annoying with complex types. But extremely useful in long method chains.