Missing checks for the bit count requirements of custom bit representations

[kleinreact]

Clash currently accepts the following example without any errors or warnings, although the number of bits marked in the individual fields exceeds the number of bits available. The additional bit requirements for the fields are simply discarded in the generated HDL.

data T where
  T0 :: Bool -> Bit -> T

{-# ANN module (DataReprAnn $(liftQ [t|T|]) 2
  [ ConstrRepr 'T0 0b11 0b00 [0b10, 0b01]
  ]) #-}

topEntity :: T
topEntity = T0 True low

[DigitalBrains1]

I feel, due to the pigeonhole principle, if we check there are no overlaps, it would follow that the bit count is correct. Whereas checking the bit count doesn't prevent overlapping assignments.

There's one aspect overlap checking does not account for (nor does counting): assigning too few bits to fields. It's related, but not the same. Or did you also mean that by "bit count"?