Split neutrals from canonical values so stuck eliminators arent encoded via constructor overloading

BidirTT/Check.lean

@@ -14,7 +14,7 @@ private def showTy (l : Lvl) (v : Val) : String :=
 mutual
   partial def check (cxt : Cxt) : Raw → Val → TCM Tm
     | .lam x t, .pi a c => do
-        let bodyTy ← cApp c (.var cxt.lvl)
+        let bodyTy ← cApp c (.neu (.var cxt.lvl))
         let t' ← check (cxt.bind x a) t bodyTy
         pure (.lam t')
     | .pair t u, .sig a c => do
@@ -62,8 +62,8 @@ mutual
         let zTy ← vApp vmotive .zero
         let z' ← check cxt z zTy
         let kCxt := cxt.bind k .nat
-        let ihTy ← vApp vmotive (.var cxt.lvl)
-        let stepTy ← vApp vmotive (.succ (.var cxt.lvl))
+        let ihTy ← vApp vmotive (.neu (.var cxt.lvl))
+        let stepTy ← vApp vmotive (.succ (.neu (.var cxt.lvl)))
         let stepBody' ← check (kCxt.bind ih ihTy) s stepTy
         let step' : Tm := .lam (.lam stepBody')
         let resultTy ← vApp vmotive vscrut
@@ -109,7 +109,7 @@ mutual
             let vtarget ← eval cxt.env target'
             if !(← conv cxt.lvl vtarget rhs) then
               throw s!"idElim target {showTy cxt.lvl vtarget} does not match the equality endpoint {showTy cxt.lvl rhs}"
-            let eqVarTy : Val := .id a x (.var cxt.lvl)
+            let eqVarTy : Val := .id a x (.neu (.var cxt.lvl))
             let (motiveBody', level) ← inferUniverse ((cxt.bind y a).bind p eqVarTy) motive
             let motive' : Tm := .lam (.lam motiveBody')
             let vmotive ← eval cxt.env motive'