Shape-irrelevance without-K broken by Agda 2.6.2

[Andreas Abel]

(AIM XXXVIII playing with cubical equality proofs for sized coinduction.)
This (ICFP 2017 paper definition) is no longer accepted by Agda >= 2.6.2:

{-# OPTIONS --without-K --sized-types --experimental-irrelevance #-}

open import Agda.Builtin.Size

data ℕ ..(s : Size) : Set where
  suc : .{t : Size< s} → ℕ t → ℕ s

Error:

.{t : Size< s} → ℕ t → ℕ s 
is not usable at the required modality @ω
when checking the constructor suc in the declaration of ℕ

[Andreas Abel]

Possibly missing applyWhen optExperimentalIrrelevance irrToNonStrict on the codomain here?

agda/src/full/Agda/TypeChecking/Irrelevance.hs

Lines 238 to 241 in 1c449e2

 Pi a b   -> usableMod domMod (unEl $ unDom a) `and2M` usableModAbs (getArgInfo a) mod (unEl <$> b) 
   where 
     domMod = mapQuantity (composeQuantity $ getQuantity a) $ 
              mapCohesion (composeCohesion $ getCohesion a) mod 

[Andreas Abel]

Possibly missing applyWhen optExperimentalIrrelevance irrToNonStrict on the codomain here?

This lets the data definition through, but trying to use it the conSplitModalityCheck barks at us. @plt-amy says this is for a reason because the transports cannot be defined.