Diagnostics

Cleat produces Rustc-style diagnostics with source context, colored underlines, and helpful suggestions.

Format

error: type mismatch: expected int, got string
  --> main.cleat:2:5
   |
 2 |     let x: int = "hello"
   |     ^

Severity levels

Suggestion hints

The compiler uses Levenshtein distance to suggest corrections:

error: unknown effect "crpyto" in fn greet
  --> main.cleat:1:27
   |
 1 | fn greet() -> int needs { crpyto } {
   |                           ^^^^^^
   = help: did you mean "crypto"?

This works for effect names, variable names, struct field names, and method names.

Suppressing warnings

cleat build main.cleat --no-warn

Useful for CI where warnings in build output are noise.

Real-time diagnostics

The language server (cleat lsp) provides these diagnostics as you type in VS Code. See Editor Setup.