Make @ViewBuilder trailing parameter positioning opt-in via .viewBuilderTrailing

Sources/SlotExamples/ActionButton.swift

@@ -1,7 +1,7 @@
 import Slots
 import SwiftUI
 
-@Slots public struct ActionButton<Label: View>: View {
+@Slots(.trailingViewBuilders) public struct ActionButton<Label: View>: View {
     var action: () -> Void
     @Slot(.text, .unlabeled) var label: Label
 

Sources/SlotExamples/Previews.swift

@@ -47,10 +47,10 @@ struct Examples_Previews: PreviewProvider {
                 // ToolbarRow examples
                 ToolbarRow(title: "Inbox")
                 ToolbarRow(
-                    title: "Details",
                     leading: {
                         Button(action: {}) { Image(systemName: "chevron.left") }
                     },
+                    title: "Details",
                     trailing: {
                         Button(action: {}) { Image(systemName: "ellipsis") }
                     })

Sources/SlotMacros/SlotMacro.swift

@@ -15,6 +15,7 @@ public struct SlotMacro: MemberMacro, ExtensionMacro {
         in context: some MacroExpansionContext
     ) throws -> [DeclSyntax] {
         let access = accessModifier(of: declaration)
+        let slotsOptions = parseSlotsOptions(from: node)
         let plain = collectPlainProperties(from: declaration)
         let slots = collectSlots(from: declaration, node: node, context: context)
         guard !slots.isEmpty else { return [] }
@@ -33,7 +34,7 @@ public struct SlotMacro: MemberMacro, ExtensionMacro {
                     declarationIndex: slot.declarationIndex
                 )
             }
-        entries.sort { ($0.tier, $0.declarationIndex) < ($1.tier, $1.declarationIndex) }
+        sortEntries(&entries, trailingViewBuilders: slotsOptions.trailingViewBuilders)
         let params = entries.map(\.param).joined(separator: ", ")
         let assignments = entries.map(\.assignment).joined(separator: "\n    ")
         let accessPrefix = access.map { "\($0) " } ?? ""
@@ -57,6 +58,7 @@ public struct SlotMacro: MemberMacro, ExtensionMacro {
         in context: some MacroExpansionContext
     ) throws -> [ExtensionDeclSyntax] {
         let access = accessModifier(of: declaration)
+        let slotsOptions = parseSlotsOptions(from: node)
         let plain = collectPlainProperties(from: declaration)
         let slots = collectSlots(from: declaration, node: node, context: context)
         guard !slots.isEmpty else { return [] }
@@ -70,7 +72,9 @@ public struct SlotMacro: MemberMacro, ExtensionMacro {
             return []
         }
 
-        let groups = extensionGroups(for: slots, plain: plain, access: access)
+        let groups = extensionGroups(
+            for: slots, plain: plain, access: access,
+            trailingViewBuilders: slotsOptions.trailingViewBuilders)
         return groups.compactMap { (whereClause, specs) in
             buildExtension(type: type, whereClause: whereClause, specs: specs)
         }
@@ -214,10 +218,30 @@ private func isFunctionType(_ type: TypeSyntax) -> Bool {
     return false
 }
 
+// MARK: - Parsing @Slots options
+
+private struct SlotsOptions {
+    var trailingViewBuilders = false
+}
+
+private func parseSlotsOptions(from attr: AttributeSyntax) -> SlotsOptions {
+    var result = SlotsOptions()
+    guard case .argumentList(let args) = attr.arguments else { return result }
+    for arg in args {
+        if arg.expression.as(MemberAccessExprSyntax.self)?.declName.baseName.text
+            == "trailingViewBuilders"
+        {
+            result.trailingViewBuilders = true
+        }
+    }
+    return result
+}
+
 // MARK: - Parameter ordering
 
-/// Parameters are sorted by tier to match SwiftUI conventions:
-/// value params first, then closures, then @ViewBuilder closures last.
+/// When `trailingViewBuilders` is enabled, parameters are sorted by tier to match
+/// SwiftUI conventions: value params first, then closures, then @ViewBuilder closures last.
+/// Otherwise, declaration order is preserved.
 private enum ParamTier: Comparable {
     case value
     case closure
@@ -231,6 +255,14 @@ private struct ParamEntry {
     let declarationIndex: Int
 }
 
+private func sortEntries(_ entries: inout [ParamEntry], trailingViewBuilders: Bool) {
+    if trailingViewBuilders {
+        entries.sort { ($0.tier, $0.declarationIndex) < ($1.tier, $1.declarationIndex) }
+    } else {
+        entries.sort { $0.declarationIndex < $1.declarationIndex }
+    }
+}
+
 private func paramEntry(for p: PlainProperty) -> ParamEntry {
     if p.isGenericView {
         return ParamEntry(
@@ -483,11 +515,13 @@ private func allCombinations(for slots: [SlotDescriptor]) -> [[SlotMode]] {
 
 /// Groups all non-trivial combinations by their where-clause key so that `.text` and `.string`
 /// variants for the same set of fixed generics land in the same extension.
-/// Parameters are sorted by tier: value params, then closures, then @ViewBuilder closures.
+/// When `trailingViewBuilders` is true, parameters are sorted by tier: value params, then
+/// closures, then @ViewBuilder closures. Otherwise, declaration order is preserved.
 private func extensionGroups(
     for slots: [SlotDescriptor],
     plain: [PlainProperty] = [],
-    access: String? = nil
+    access: String? = nil,
+    trailingViewBuilders: Bool = false
 ) -> [(whereClause: String, specs: [InitSpec])] {
     // Use an ordered structure to preserve natural combo order
     var order: [String] = []
@@ -606,7 +640,7 @@ private func extensionGroups(
             }
         }
 
-        entries.sort { ($0.tier, $0.declarationIndex) < ($1.tier, $1.declarationIndex) }
+        sortEntries(&entries, trailingViewBuilders: trailingViewBuilders)
 
         let key = constraints.joined(separator: ", ")
         let spec = InitSpec(

Sources/Slots/Slots.swift

@@ -17,4 +17,4 @@ import SwiftUI
 /// ```
 @attached(member, names: named(init))
 @attached(extension, names: named(init))
-public macro Slots() = #externalMacro(module: "SlotMacros", type: "SlotMacro")
+public macro Slots(_ options: SlotsOption...) = #externalMacro(module: "SlotMacros", type: "SlotMacro")

Sources/Slots/SlotsOption.swift

@@ -0,0 +1,13 @@
+import SwiftUI
+
+public struct SlotsOption: Sendable, Equatable {
+    private let id: Int
+
+    private init(id: Int) {
+        self.id = id
+    }
+
+    /// Reorder generated init parameters so `@ViewBuilder` closures appear last,
+    /// enabling trailing closure syntax.
+    public static let trailingViewBuilders = SlotsOption(id: 0)
+}

Tests/SlotTests/SlotIntegrationTests.swift

@@ -119,7 +119,7 @@ final class SlotIntegrationTests: XCTestCase {
             isSelected: false, leading: { Image(systemName: "star") }, content: { Text("hi") }, trailing: { Text("→") })
         // LocalizedStringResource content, generic leading + trailing
         let _: Row<Image, Text, Text> = Row(
-            isSelected: true, content: "hi", leading: { Image(systemName: "star") }, trailing: { Text("→") })
+            isSelected: true, leading: { Image(systemName: "star") }, content: "hi", trailing: { Text("→") })
         // image leading, LocalizedStringResource content, generic trailing
         let _: Row<Image, Text, Text> = Row(
             isSelected: false, leadingSystemName: "star", content: "hi", trailing: { Text("→") })