readNew metastability warning

[dopamane]

Using Clash 0.99.3, the readNew function causes compiler warnings. The following example:

module TopLevel where

import Clash.Prelude

topEntity
  :: Clock System Source
  -> Reset System Asynchronous
  -> Signal System (Unsigned 5)
  -> Signal System (Maybe (Unsigned 5, BitVector 5))
  -> Signal System (BitVector 5)
topEntity = exposeClockReset test

test :: HiddenClockReset dom gated sync
       => Signal dom (Unsigned 5)
       -> Signal dom (Maybe (Unsigned 5, BitVector 5))
       -> Signal dom (BitVector 5)
test rdAddr	wrM = readNew (asyncRam d32) rdAddr wrM

Produces the compiler warning:

Loading dependencies took 0.499845074s
Compiling: TopLevel.topEntity
TopLevel.$sreadNew45574 (:: GHC.Classes.IP
  rst
  (Clash.Signal.Internal.Reset
     (Clash.Signal.Internal.Dom system 10000)
     Clash.Signal.Internal.Asynchronous)
-> GHC.Classes.IP
     clk
     (Clash.Signal.Internal.Clock
        (Clash.Signal.Internal.Dom system 10000)
        Clash.Signal.Internal.Source)
-> Clash.Signal.Internal.Clock
     (Clash.Signal.Internal.Dom system 10000)
     Clash.Signal.Internal.Source
-> Clash.Signal.Internal.Signal
     (Clash.Signal.Internal.Dom system 10000)
     (Clash.Sized.Internal.Unsigned.Unsigned 5)
-> Clash.Signal.Internal.Signal
     (Clash.Signal.Internal.Dom system 10000)
     (GHC.Base.Maybe
        (GHC.Tuple.(,)
           (Clash.Sized.Internal.Unsigned.Unsigned 5)
           (Clash.Sized.Internal.BitVector.BitVector 5)))
-> Clash.Sized.Internal.BitVector.BitVector 5)
has potentially dangerous meta-stability issues:

The following clocks:
* GHC.Classes.IP
  clk
  (Clash.Signal.Internal.Clock
     (Clash.Signal.Internal.Dom system 10000)
     Clash.Signal.Internal.Source)
* Clash.Signal.Internal.Clock
  (Clash.Signal.Internal.Dom system 10000)
  Clash.Signal.Internal.Source
belong to the same clock domain and should be connected to the same clock source in order to prevent meta-stability issues.
Applied 127 transformations
Normalisation took 0.342218385s
Netlist generation took 0.003322493s
Total compilation took 0.846340327s

From what I can tell, there should not be meta-stability issues nor clock connection issues. Removing the readNew results in no compiler warnings, as expected.

[christiaanb]

The code for this warning should really be revisited before the 1.0 release

[martijnbastiaan]

This warning has been removed in #493, as it produced too many false positives. Leaving this report open as we do want a warning like it again.