Remove some ambiguities in parsing

playground/samples/Tree.newt

@@ -3,7 +3,6 @@ module Tree
 -- adapted from Conor McBride's 2-3 tree example
 -- youtube video: https://youtu.be/v2yXrOkzt5w?t=3013
 
-
 data Nat : U where
   Z : Nat
   S : Nat -> Nat
@@ -16,8 +15,8 @@ data Void : U where
 infixl 4 _+_
 
 data _+_ : U -> U -> U where
-  inl : {A B} -> A -> A + B
-  inr : {A B} -> B -> A + B
+  inl : ∀ a b. a -> a + b
+  inr : ∀ a b. b -> a + b
 
 infix 4 _<=_
 
@@ -47,14 +46,14 @@ _ <<= Top = Unit
 _ <<= _ = Void
 
 data Intv : Bnd -> Bnd -> U where
-  intv : {l u} (x : Nat) (lx : l <<= N x) (xu : N x <<= u) -> Intv l u
+  intv : ∀ l u. (x : Nat) (lx : l <<= N x) (xu : N x <<= u) -> Intv l u
 
 data T23 : Bnd -> Bnd -> Nat -> U where
-  leaf : {l u} (lu : l <<= u) -> T23 l u Z
-  node2 : {l u h} (x : _)
+  leaf : ∀ l u. (lu : l <<= u) -> T23 l u Z
+  node2 : ∀ l u h. (x : _)
     (tlx : T23 l (N x) h) (txu : T23 (N x) u h) ->
     T23 l u (S h)
-  node3 : {l u h} (x y : _)
+  node3 : ∀ l u h. (x y : _)
     (tlx : T23 l (N x) h) (txy : T23 (N x) (N y) h) (tyu : T23 (N y) u h) ->
     T23 l u (S h)
 
@@ -66,12 +65,12 @@ data Sg : (A : U) -> (A -> U) -> U where
   _,_ : {A : U} {B : A -> U} -> (a : A) -> B a -> Sg A B
 
 _*_ : U -> U -> U
-A * B = Sg A (\ _ => B)
+a * b = Sg a (\ _ => b)
 
 TooBig : Bnd -> Bnd -> Nat -> U
 TooBig l u h = Sg Nat (\ x => T23 l (N x) h * T23 (N x) u h)
 
-insert : {l u h} -> Intv l u -> T23 l u h -> TooBig l u h + T23 l u h
+insert : ∀ l u h. Intv l u -> T23 l u h -> TooBig l u h + T23 l u h
 insert (intv x lx xu) (leaf lu) = inl (x , (leaf lx , leaf xu))
 insert (intv x lx xu) (node2 y tly tyu) = case cmp x y of
   -- u := N y is not solved at this time