Do literal integral values have a specific type in Rust?

Question

In https://doc.rust-lang.org/book/primitive-types.html#numeric-types, it said that in

let x = 42; // x has type i32

That means

Answer 1

From the language reference:

The type of an unsuffixed integer literal is determined by type inference:

• If an integer type can be uniquely determined from the surrounding program context, the unsuffixed integer literal has that type.

• If the program context under-constrains the type, it defaults to the signed 32-bit integer i32.

• If the program context over-constrains the type, it is considered a static type error.

On the line

println!("{}", v[1]); // is 1 a usize?

the surrounding program context requires 1 to be an usize (because that's what the [] operator needs), so yes, here 1 will have the type usize.