ecko check

ecko check file.ecko
ecko check src/

Static analysis. It is also run automatically before every ecko file.ecko, where an error-level finding stops the program before its first line.

What it finds

Errors (these stop a run):

• Undefined names, with a did-you-mean suggestion for near misses.
• Wrong arity - calling a function with too few or too many arguments,

including the built-ins.

• Use before definition at the top level.
• Non-exhaustive match - a variant with no arm and no _.
• Unknown struct or variant members.
• Unwrapped credentials - a secret value used where the plain value is

required, without reveal.

Warnings (reported, do not stop a run):

• Unused bindings, scope-aware, so a name used only inside a nested closure is

not flagged.

• Unused imports.
• Shadowing a built-in, which is legal and occasionally deliberate - the

core.* escape hatch exists for exactly that case.

• Deprecated syntax, with the migration (ecko fmt) named.

Why a dynamic language gates on this

Ecko has no static type system, and adding one is not the plan. But the errors above are not type errors - they are definitely wrong regardless of types. A misspelled function name is never correct. A match missing a variant is never correct. Finding those before execution costs nothing and removes the most common way a script fails halfway through doing something it cannot undo.

The same analysis backs ecko lsp, so an editor shows these findings as you type.

Exit status

0 when there is nothing at error level. Non-zero otherwise. Warnings alone do not change the exit status, so ecko check is usable as a CI gate without forcing warning-free code.