# assert

Unavailable statement; use an explicit check and error

Last updated: 2026-09-09

Package: language | Status: unavailable

Tags: boundaries, cpu, keyword, language, yeho

Use the replacement that makes ownership and flow explicit. Revisit dedicated syntax only after it earns a compiler, runtime, and verification contract.

```yh
assert
```


## Complete program

A complete example you can paste into start.yh.

Verification: type checked

```yh
// assert is not admitted; validate explicitly.
int score = 10
if score < 0 { Console.Error("Score must be nonnegative") }
else { Console.Log(Text.From(score)) }

```

Save this beside start.yh as project.mech:

```toml
manifestVersion = "2"
package = "api.example.word__assert"
version = "0.1.0"
languageEdition = "yeho-core-2026.1"

[app]
kind = "headless"

```

Extract the example archive beside the yeho and dolphin checkouts. This example requires those source dependencies and a current developer compiler.

```sh
./yeho/build/dolphin-metal/yehoc ./api-examples/word--assert/complete --backend cpu-oracle -o /tmp/yeho-example
/tmp/yeho-example
```


panic, assert, fatal, exception subclasses, and finally are not admitted error syntax.

Dedicated event, emit, and watch syntax is deferred in favor of ordinary values, functions, tasks, and tunnels.

Source: yeho/parser_core.cpp and parser_statements.cpp rejection diagnostics; language-core.md §13.4

AI training permission: https://demonhunterlabs.com/ai-use