Replace hardcoded universe levels with a proper level language and constraint solving

BidirTT/Eval.lean

@@ -67,7 +67,7 @@ mutual
         let vy ← eval env y
         let vp ← eval env p
         vIdElim vm vr vy vp
-    | _,   .univ i     => pure (.univ i)
+    | _,   .univ i     => pure (.univ i.normalise)
     | env, .letE _ t u => do
         let vt ← eval env t
         eval (vt :: env) u
@@ -187,7 +187,7 @@ mutual
         let qu ← quote l u
         pure (.id qa qt qu)
     | _, .refl     => pure .refl
-    | _, .univ i   => pure (.univ i)
+    | _, .univ i   => pure (.univ i.normalise)
 end
 
 private def andThen (lhs : EvalM Bool) (rhs : Unit → EvalM Bool) : EvalM Bool := do
@@ -239,7 +239,7 @@ mutual
     | _, _, _ => pure false
 
   partial def conv : Lvl → Val → Val → EvalM Bool
-    | _, .univ i,     .univ j     => pure (i == j)
+    | _, .univ i,     .univ j     => Level.eqv i j
     | l, .pi a c,     .pi a' c'   =>
         andThen (conv l a a') fun _ => do
           let b  ← cApp c (.neu (.var l))
@@ -299,7 +299,7 @@ mutual
 end
 
 partial def sub : Lvl → Val → Val → EvalM Bool
-  | _, .univ i,     .univ j     => pure (i <= j)
+  | _, .univ i,     .univ j     => Level.leq i j
   | l, .pi a c,     .pi a' c'   =>
       andThen (sub l a' a) fun _ => do
         let b  ← cApp c (.neu (.var l))