Writing a lambda-inspecting compiler extension

1

I would like to write a compiler extension and/or annotation processor that does the following:

  1. is triggered by the presence of a specific annotation on a lambda:

    @Target(AnnotationTarget.FUNCTION)
annotation class MyAnnotation

val someLambda = @MyAnnotation { n: Int -> n + 1 }

  2. can inspect (read-only) the Kotlin AST of the lambda;

  3. can fail the compilation with an error, for example if the code inside the lambda contains a Kotlin feature that is not supported by my library;

  4. generates data (not code!) that will be used by a runtime library, either by creating new source files or (better) by storing the data as further annotations to the lambda being compiled.

Iā€™m looking at the interfaces in org.jetbrains.kotlin.extensions, but they are somewhat complicated and undocumented.

Can anybody recommend the simplest way to achieve the points above?

2

Interesting indeed. I have my own use case for such a compiler extension (unfortunately compiler plugins are not quite stable yet). What I want is the ability to declare on a function parameter that the function cannot capture the this pointer (or other local variables) implicitly.

3

Does anybody have any idea how to implement something like this? Can a standard (kapt) annotation processor inspect the original Kotlin AST?

4

No. You need a compiler plugin for that.

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