const inside a function

Built from the repository at commit a8614dc.

A constant is declared at the top level, beside fn and class. Inside a function, a value that does not change is a let.

Why

A const names one value for the whole program, and its value is known at compile time. A let in a function already gives a name that cannot change, and its value may come from anything in scope. Replacing const with let is always right.

Broken

fn main() {
    const limit = 100
    print(limit)
}

What sisu says

error[E0084]: `const` is declared at the top level
 --> E0084.sisu:2:5
  |
2 |     const limit = 100
  |     ^^^^^
  |
help: use `let`
  |
2 -     const limit = 100
2 +     let limit = 100
  |

sisu: 1 error
sisu: for more on a code, run `sisu explain <code>`: E0084

Fixed

fn main() {
    let limit = 100
    print(limit)
}

Related

• E0085: constant of a type that cannot be folded.