Removed tuple type, introduced kwargs to filter signature

Sources/Liquid/Expression.swift

@@ -12,8 +12,6 @@ struct Expression: CustomStringConvertible {
 		switch kind {
 		case let .lookup(lookup):
 			return lookup.map { $0.description }.joined(separator: "/")
-		case .namedParam(let value):
-			return "\(value.0): \(value.1.description)"
 		case .variable(let key):
 			return key
 		case .filter(let filter):
@@ -33,7 +31,6 @@ struct Expression: CustomStringConvertible {
 
 	indirect enum Kind {
 		case lookup([Expression])
-		case namedParam(key: String, expression: Expression)
 		case variable(key: String)
 		case filter(LookupFilter)
 		case value(Value)
@@ -66,10 +63,6 @@ struct Expression: CustomStringConvertible {
 		self.kind = .lookup(lookup)
 	}
 
-	init(key: String, expression: Expression) {
-		self.kind = .namedParam(key: key, expression: expression)
-	}
-
 	func evaluate(context: Context) -> Value {
 		return evaluate(context: context, data: nil)
 	}
@@ -82,8 +75,6 @@ struct Expression: CustomStringConvertible {
 			for expression in expressions.dropFirst() {
 				result = expression.evaluate(context: context, data: result)
 			}
-		case let .namedParam(key, expression):
-			result = Value((key, expression.evaluate(context: context, data: data)))
 		case let .variable(key):
 			if let data = data {
 				result = data.lookup(Value(key), encoder: context.encoder)
@@ -108,11 +99,11 @@ struct Expression: CustomStringConvertible {
 				} else {
 					switch filter {
 					case .size:
-						result = try? Filters.sizeFilter(value: data, args: [], encoder: context.encoder)
+						result = try? Filters.sizeFilter(value: data, args: [], kwargs: [:], encoder: context.encoder)
 					case .first:
-						result = try? Filters.firstFilter(value: data, args: [], encoder: context.encoder)
+						result = try? Filters.firstFilter(value: data, args: [], kwargs: [:], encoder: context.encoder)
 					case .last:
-						result = try? Filters.lastFilter(value: data, args: [], encoder: context.encoder)
+						result = try? Filters.lastFilter(value: data, args: [], kwargs: [:], encoder: context.encoder)
 					}
 				}
 			} else {