ChiselSim does not properly support views (e.g. FlatIO)

[jackkoenig]

Type of issue: Bug Report

Please provide the steps to reproduce the problem:

Try the following code:

//> using scala "2.13.12"
//> using dep "org.chipsalliance::chisel:6.3.0"
//> using plugin "org.chipsalliance:::chisel-plugin:6.3.0"
//> using options "-unchecked", "-deprecation", "-language:reflectiveCalls", "-feature", "-Xcheckinit", "-Xfatal-warnings", "-Ywarn-dead-code", "-Ywarn-unused", "-Ymacro-annotations"

import chisel3._
import chisel3.simulator.EphemeralSimulator._
// _root_ disambiguates from package chisel3.util.circt if user imports chisel3.util._
import _root_.circt.stage.ChiselStage

class Foo extends Module {
  val io = FlatIO(new Bundle {
    val in = Input(UInt(8.W))
    val out = Output(UInt(8.W))
  })

  val delay = RegNext(io.in)
  io.out := delay
}

object Main extends App {
  println(
    ChiselStage.emitSystemVerilog(
      gen = new Foo,
      firtoolOpts = Array("-disable-all-randomization", "-strip-debug-info")
    )
  )
  simulate(new Foo) { c =>
    c.io.in.poke(12.U)
    c.clock.step()
    c.io.out.peek()
  }
}

What is the current behavior?

Verilog generates just fine, but ChiselSim throws an exception:

Exception in thread "main" java.util.NoSuchElementException: key not found: Foo.in: IO[UInt<8>]
        at scala.collection.immutable.Map$Map4.apply(Map.scala:535)
        at chisel3.simulator.package$AnySimulatedModule.port(package.scala:36)
        at chisel3.simulator.PeekPokeAPI$testableData.poke(PeekPokeAPI.scala:116)
        at chisel3.simulator.PeekPokeAPI$testableData.poke(PeekPokeAPI.scala:111)

What is the expected behavior?

This should work just fine

Please tell us about your environment:

Other Information

Derived from question on Gitter¹.

What is the use case for changing the behavior?

Correct behavior

Footnotes

1. https://matrix.to/#/!jSbgpvvpsPbLpsLZOC:matrix.org/$a1ygVO22ceENy_lUNaTNuqOv-cGaM1oa2IxVSsRKPQ8?via=matrix.org&via=gitter.im&via=mumblingdrunkard.com ↩