fun/web/documentation/errors-and-diagnostics.md

layout	published	noToc	noComments	noDate	title	subtitle	description	permalink	lang	tags
page	true	true	false	false	Fun - Errors and Diagnostics	Understanding parser/runtime errors and enabling diagnostics.	Understanding parser/runtime errors and enabling diagnostics.	/documentation/errors-and-diagnostics/	en	documentation handbook installation usage introduction help guide howto docs specifications specs repl

Errors and Diagnostics

This guide helps you understand common error messages and how to collect useful diagnostics.

Common error classes

• Parse errors: syntax/indentation problems detected before execution.
• Name/lookup errors: missing variables, functions, or modules.
• Runtime errors: type mismatches, out-of-range access, invalid operations.

Enabling diagnostics

• Build with -DFUN_DEBUG=ON to enable additional assertions and debug messages (see build.md).
• Run with smaller, focused scripts to isolate issues.

Getting useful reports

• Capture the minimal script that reproduces the issue.
• Note your build options and platform.
• Record the full error output from the CLI (fun), including line/column if present.

Tips

• Use prints or logging sparingly to narrow down failing code.
• Start from a passing simple case and add complexity until it breaks.