make typechecker actually pass the dimeq to subT

also erase some length arguments

lib/Quox/Syntax/DimEq.idr

@@ -104,10 +104,10 @@ mutual
 
   export %inline
   setVar : (i, j : Var d) -> DimEq' d -> DimEq d
-  setVar i j eqs with (compareP i j)
-    _              | IsLT lt = setVar' i j lt eqs
-    setVar i i eqs | IsEQ    = C eqs
-    _              | IsGT gt = setVar' j i gt eqs
+  setVar i j eqs = case compareP i j of
+    IsLT lt => setVar' i j lt eqs
+    IsEQ    => C eqs
+    IsGT gt => setVar' j i gt eqs
 
 
 export %inline