Can't set DontCare for Analog wires using bulk connect (<>)

[edwardcwang]

Type of issue: bug report

Impact: API addition (no impact on existing code)?

Development Phase: request

Trying to set an Analog wire to DontCare using <> causes an error. Example:

import chisel3._
import chisel3.experimental._
class AnalogDontCareTestModule extends Module {
 val io = IO(new Bundle {
   val out = Vec(2, Analog(1.W))
   val in = Analog(1.W)
 })
 io.out(0) <> io.in
 io.out(1) := DontCare
 // io.out(1) <> DontCare // <-- doesn't work
}

Error message:

java.lang.RuntimeException: Unexpected port element direction 'Bidirectional(Default)'
  chisel3.core.BindingDirection$.from(Binding.scala:66)
  chisel3.core.BiConnect$.elemConnect(BiConnect.scala:216)
  chisel3.core.BiConnect$.connect(BiConnect.scala:68)
  chisel3.core.Data.bulkConnect(Data.scala:322)
  chisel3.core.Data.$less$greater(Data.scala:366)

This is strange as a user since := is generally verboten for Analog but I'm forced to use := for DontCare on Analog. It seems natural to allow Analogs to be set to DontCare using <>.

[redpanda3]

I suggest to delete <>, since <> and := are the same function within a data...