Bytecode in compiled class failed to pass verify when calling methods with argument

[fifth-light]

I want to integrate mocha into my model rendering mod ArmorStand.

To learn how to bind objects into mocha, I wrote a small test. However it failed when compiling molang into bytecode:

import team.unnamed.mocha.MochaEngine
import team.unnamed.mocha.runtime.binding.Binding

@Binding("plain")
class NoArgument(var offset: Int) {
    @Binding("calc")
    fun calc(): Double = offset.toDouble()
}

@Binding("offset")
class WithOffset(var offset: Int) {
    @Binding("calc")
    fun calc(value: Double): Double = value + offset.toDouble()
}

fun main() {
    val engine = MochaEngine.createStandard()

    val plain = NoArgument(0)
    engine.bindInstance(NoArgument::class.java, plain, "plain")

    val plainExpr = "plain.calc()"

    val plainInterpreted = engine.prepareEval(plainExpr)
    plain.offset = 3
    println(plainInterpreted.evaluate())
    plain.offset = 4
    println(plainInterpreted.evaluate())

    val plainCompiled = engine.compile(plainExpr)
    plain.offset = 3
    println(plainCompiled.evaluate())
    plain.offset = 4
    println(plainCompiled.evaluate())

    val offset = WithOffset(0)
    engine.bindInstance(WithOffset::class.java, offset, "offset")

    val offsetExpr = "offset.calc(1)"

    val offsetInterpreted = engine.prepareEval(offsetExpr)
    offset.offset = 3
    println(offsetInterpreted.evaluate())
    offset.offset = 4
    println(offsetInterpreted.evaluate())

    val offsetCompiled = engine.compile(offsetExpr)
    offset.offset = 3
    println(offsetCompiled.evaluate())
    offset.offset = 4
    println(offsetCompiled.evaluate())
}

Output:

INFO: Running command line: bazel-bin/mocha-test/mocha-test
3.0
4.0
3.0
4.0
4.0
5.0
Exception in thread "main" java.lang.VerifyError: Bad type on operand stack
Exception Details:
  Location:
    team/unnamed/mocha/runtime/MolangFunctionImpl_MochaFunction_evaluate_19977c0e2e9_d.evaluate()D @5: invokevirtual
  Reason:
    Type 'WithOffset' (current frame, stack[2]) is not assignable to double_2nd
  Current Frame:
    bci: @5
    flags: { }
    locals: { 'team/unnamed/mocha/runtime/MolangFunctionImpl_MochaFunction_evaluate_19977c0e2e9_d' }
    stack: { double, double_2nd, 'WithOffset' }
  Bytecode:
    0000000: 0f2a b400 0cb6 0012 af                 

        at java.base/java.lang.ClassLoader.defineClass0(Native Method)
        at java.base/java.lang.System$2.defineClass(System.java:2394)
        at java.base/java.lang.invoke.MethodHandles$Lookup$ClassDefiner.defineClass(MethodHandles.java:2505)
        at java.base/java.lang.invoke.MethodHandles$Lookup$ClassDefiner.defineClass(MethodHandles.java:2480)
        at java.base/java.lang.invoke.MethodHandles$Lookup.defineClass(MethodHandles.java:1865)
        at javassist.util.proxy.DefineClassHelper.toClass(DefineClassHelper.java:295)
        at javassist.util.proxy.DefineClassHelper$Java11.defineClass(DefineClassHelper.java:48)
        at javassist.util.proxy.DefineClassHelper.toClass(DefineClassHelper.java:260)
        at javassist.ClassPool.toClass(ClassPool.java:1240)
        at team.unnamed.mocha.runtime.MolangCompiler.compile(MolangCompiler.java:291)
        at team.unnamed.mocha.MochaEngineImpl.compile(MochaEngineImpl.java:186)
        at team.unnamed.mocha.MochaEngine.compile(MochaEngine.java:267)
        at team.unnamed.mocha.MochaEngine.compile(MochaEngine.java:281)
        at MochaTestKt.main(MochaTest.kt:47)
        at MochaTestKt.main(MochaTest.kt)