MoonBit Deprecated Syntax Reference

Reference this skill before generating MoonBit code to avoid deprecated patterns.

Deprecated Patterns

Error Propagation: ! suffix (DEPRECATED)

Old syntax (deprecated):

let result = may_fail()!  // WRONG: ! suffix

Current syntax:

// Automatic propagation when caller also declares `raise`
fn caller() -> T raise E {
  let result = may_fail()  // Errors propagate automatically
}

// Or explicit try/catch
try {
  may_fail()
} catch {
  e => handle(e)
}

Labeled Arguments: ~ prefix vs suffix

Old syntax (deprecated):

fn foo(~label : Int) -> Unit  // WRONG: ~ prefix
foo(~label=42)                // WRONG: ~ prefix in call

Current syntax:

fn foo(label~ : Int) -> Unit  // Correct: ~ suffix
foo(label~=42)                // Correct: ~ suffix in call
foo(label=42)                 // Also valid without ~

Maintenance

When the AI generates code that fails due to deprecated syntax:

1. •Add the deprecated pattern to this file
2. •Include the old (wrong) and new (correct) syntax
3. •Add a brief explanation

This file is the source of truth for deprecated MoonBit patterns in this project.