inferred.md

r[type.inferred]

Inferred type

r[type.inferred.syntax]

^Syntax
InferredType : _

r[type.inferred.intro] The inferred type asks the compiler to infer the type if possible based on the surrounding information available.

r[type.inferred.constraint] It cannot be used in item signatures.

It is often used in generic arguments:

let x: Vec<_> = (0..10).collect();