XO0402: type arguments cannot be inferred

A generic function’s type parameter was determined by nothing: not the arguments, the expected type, or later use. Write the type argument explicitly (json.decode[Int](b)), or give the result an expected type. See core 2.7.

Example

use std/json

fn f(b: Bytes) -> Int {
  let _ = json.decode(b).ok()
  1
}

Fix

use std/json

fn f(b: Bytes) -> Int {
  let _ = json.decode[Int](b).ok()
  1
}

Run xo explain XO0402 for this text in a terminal, or see section 10.6 of the specification.