Readable errors

The problem: A compiler message that talks about lifetimes and borrowing sends you away from your own code.
An example: You change a value that you declared without mut.
What Nikaia checks: The compiler points at every place the explanation needs: ^ under the line with the mistake, - under the line that explains it. Then it says what to write instead. Errors point at your .nika line and do not talk about lifetimes or borrowing.
The limit: When no line of yours explains an error, the message says so. Where a check passes a problem on to the Rust compiler underneath, the error it raises is reported against your .nika line.

What the compiler says

error[NK1139]: You're changing `count`, but it wasn't declared as mutable.
  --> app.nika:4:9
   |
 2 |     let count = 0
   |         ----- declared here without `mut`
   ...
 4 |         count += n
   |         ^^^^^ changed here
   |
   = help: Add `mut` where it's declared: `let mut count`.

Go deeper

More under Easy to understand: Code that waits needs no marking Formats are part of the language