JVM: generation of benchmark methods returning value classes fails

[fzhinkin]

Kotlin compiler mangles name of functions returning value classes. JMH can't handle such method names and fails with a cryptic error:

@JvmInline
value class Val(val value: Int)

@State(Scope.Benchmark)
open class ValueClassBenchmark {
    @Benchmark
    fun benchmark() = Val(42)
}

Generation of JMH bytecode failed with 1 errors:
  - Group name should be the legal Java identifier.
   [org.openjdk.jmh.generators.reflection.RFMethodInfo@2e052ab3]

Under the missing RFMethodInfo.toString overload the following function is hiding: org.example.ValueClassBenchmark.benchmark-5sfh64U.

Using @JvmName or rewriting the benchmark method to accept a blackhole and use it explicitly instead of returning a value class instance helps, but the solution is not that intuitive (and org.openjdk.jmh.generators.reflection.RFMethodInfo@2e052ab3 does not help here).

Perhaps, we should check method names in JmhBytecodeGeneratorWorker before passing classes down to JMH and print some meaningful error message with a fix suggestion.