title: How to get type hints to display?
body: <p>I have seen youtubers and such working on Rust in VSC with rust-analyzer plug-in where they get the optional type annotations displayed, even if it isn't necessarily written in the code. It's like I type <code>foo(a,b)</code> in the editor and it automagically displays <code>foo(a: A, b: B)</code> where the <code>:A</code> and <code>:B</code> are in faint grey possibly not even written in the file, just visual hint? It's nice and I can't figure out whether this is a feature of VSC or rust-analyzer? My rust-analyzer has the two settings Parameter Hints and TypeHints both set to enabled.</p>