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kotlinlang

I'm writing a DSL with a complex DSL based on type parameters. Is there a simple way I can have a test that some code _doesn't_ compile? I'd like to be sure that illegal cases are indeed caught by the compiler going forward.

You could use the compiler test framework

It requires some kind of setup but it is small

Do you have a very small example of what it would look like? Even just a screenshot of an existing similar test would be useful

It would be something like this
```fun f(x: Any) = x <!UNCHECKED_CAST!>as Array&lt;String&gt;&lt;!&gt;```

So the test itself is a pair of `.kt` files with the code you want to test and generated method with `@Test` annotation.
When you run the test, the framework runs the compiler over `.kt` file and renders all reported warnings/errors directly inside this `.kt` file in `<!DIAGNOSTIC_NAME!>...code on which error is reported...&lt;!&gt;` format

I use this code: <https://github.com/hfhbd/validation/tree/main/kotlin-plugin|https://github.com/hfhbd/validation/tree/main/kotlin-plugin> see the test fixtures folder. It is the official kotlin compiler test framework only with more Gradle standard setup (instead using the JPMS folder style). The tests are in the resources folder. 

box tests requires a fun main: String returning „OK“, diagnostic tests are usable for, well, diagnostic, like failed compilations. 

This is the sample you are looking for: <https://github.com/hfhbd/validation/blob/main/kotlin-plugin/src/testFixtures/resources/testData/diagnostics/wrongType.kt|https://github.com/hfhbd/validation/blob/main/kotlin-plugin/src/testFixtures/resources/testData/diagnostics/wrongType.kt>