# E4190

Compiler diagnostic name: `mbt_check_fatal_error`.

Fatal syntax error in an `mbt check` documentation block.

Code fences marked as `mbt check` in doc comments are parsed as document tests.
If a block contains fatal syntax errors, MoonBit skips that block and reports
this diagnostic on the code fence.

## Erroneous example

The following doc comment has an incomplete `let` binding inside an `mbt check`
block:

```{literalinclude} /sources/error_codes/4190_error/top.mbt
:language: moonbit
```

MoonBit will report an error.

## Suggestion

Fix the syntax inside the documentation block. When the block is meant to be
checked as a doctest, wrap executable statements in `test { ... }`:

```{literalinclude} /sources/error_codes/4190_fixed/top.mbt
:language: moonbit
```