What is the r#""# operator in Rust?

I saw the operator r#"" in Rust but I can't find what it does. It came in handy for creating JSON:

let var1 = "test1";
let json = r#"{"type": "type1", "type2": var1}"#;
println!("{}", json) // => {"type2": "type1", "type2": var1}

What's the name of the operator r#""? How do I make var1 evaluate?

I can't find what it does

It has to do with string literals and raw strings. I think it is explained pretty well in this part of the documentation, in the code block that is posted there you can see what it does:

"foo"; r"foo";                     // foo
"\"foo\""; r#""foo""#;             // "foo"

"foo #\"# bar";
r##"foo #"# bar"##;                // foo #"# bar

"\x52"; "R"; r"R";                 // R
"\\x52"; r"\x52";                  // \x52

It negates the need to escape special characters inside the string.

Stack Overflow Q#26611664, score: 164