         }
     }
 
-    // Note: thrown error is always a SymbolError
+    // Note: thrown error is always a LayoutError
     private var _settingUpExpressions = false
     private var _expressionsSetUp = false
     private func setUpExpressions() throws {

            return try getter()
        }
        assert(expressions[symbol] == nil)
        let getter: () throws -> Any
        switch symbol {
        case "left":

        }
        try completeSetup()
        for symbol in expressions.keys {
            try LayoutError.wrap({ try setUpExpression(for: symbol) }, for: self)
        }

        #if arch(i386) || arch(x86_64)
