Make all AdditionalTrailingClosures children non-optional

Author: ahoppen

CodeGeneration/Sources/SyntaxSupport/Child.swift

@@ -32,7 +32,7 @@ public enum ChildKind {
   /// The child always contains a node that matches one of the `choices`.
   case nodeChoices(choices: [Child])
   /// The child is a collection of `kind`.
-  case collection(kind: SyntaxNodeKind, collectionElementName: String, deprecatedCollectionElementName: String? = nil)
+  case collection(kind: SyntaxNodeKind, collectionElementName: String, defaultsToEmpty: Bool = false, deprecatedCollectionElementName: String? = nil)
   /// The child is a token that matches one of the given `choices`.
   /// If `requiresLeadingSpace` or `requiresTrailingSpace` is not `nil`, it
   /// overrides the default leading/trailing space behavior of the token.
@@ -91,7 +91,7 @@ public class Child {
       return kind
     case .nodeChoices:
       return .syntax
-    case .collection(kind: let kind, _, _):
+    case .collection(kind: let kind, _, _, _):
       return kind
     case .token:
       return .token
@@ -150,7 +150,7 @@ public class Child {
   /// Whether this child has syntax kind `UnexpectedNodes`.
   public var isUnexpectedNodes: Bool {
     switch kind {
-    case .collection(kind: .unexpectedNodes, _, _):
+    case .collection(kind: .unexpectedNodes, _, _, _):
       return true
     default:
       return false
@@ -165,7 +165,7 @@ public class Child {
       return choices.isEmpty
     case .node(let kind):
       return kind.isBase
-    case .collection(let kind, _, _):
+    case .collection(kind: let kind, _, _, _):
       return kind.isBase
     case .token:
       return false

CodeGeneration/Sources/SyntaxSupport/DeclNodes.swift

@@ -1450,8 +1450,7 @@ public let DECL_NODES: [Node] = [
       ),
       Child(
         name: "AdditionalTrailingClosures",
-        kind: .collection(kind: .multipleTrailingClosureElementList, collectionElementName: "AdditionalTrailingClosure"),
-        isOptional: true
+        kind: .collection(kind: .multipleTrailingClosureElementList, collectionElementName: "AdditionalTrailingClosure", defaultsToEmpty: true)
       ),
     ]
   ),

CodeGeneration/Sources/SyntaxSupport/ExprNodes.swift

@@ -828,9 +828,8 @@ public let EXPR_NODES: [Node] = [
       ),
       Child(
         name: "AdditionalTrailingClosures",
-        kind: .collection(kind: .multipleTrailingClosureElementList, collectionElementName: "AdditionalTrailingClosure"),
-        nameForDiagnostics: "trailing closures",
-        isOptional: true
+        kind: .collection(kind: .multipleTrailingClosureElementList, collectionElementName: "AdditionalTrailingClosure", defaultsToEmpty: true),
+        nameForDiagnostics: "trailing closures"
       ),
     ]
   ),
@@ -1179,8 +1178,7 @@ public let EXPR_NODES: [Node] = [
       ),
       Child(
         name: "AdditionalTrailingClosures",
-        kind: .collection(kind: .multipleTrailingClosureElementList, collectionElementName: "AdditionalTrailingClosure"),
-        isOptional: true
+        kind: .collection(kind: .multipleTrailingClosureElementList, collectionElementName: "AdditionalTrailingClosure", defaultsToEmpty: true)
       ),
     ]
   ),
@@ -1583,9 +1581,8 @@ public let EXPR_NODES: [Node] = [
       ),
       Child(
         name: "AdditionalTrailingClosures",
-        kind: .collection(kind: .multipleTrailingClosureElementList, collectionElementName: "AdditionalTrailingClosure"),
-        nameForDiagnostics: "trailing closures",
-        isOptional: true
+        kind: .collection(kind: .multipleTrailingClosureElementList, collectionElementName: "AdditionalTrailingClosure", defaultsToEmpty: true),
+        nameForDiagnostics: "trailing closures"
       ),
     ]
   ),

CodeGeneration/Sources/SyntaxSupport/GrammarGenerator.swift

@@ -36,7 +36,7 @@ struct GrammarGenerator {
     case .nodeChoices(let choices):
       let choicesDescriptions = choices.map { grammar(for: $0) }
       return "(\(choicesDescriptions.joined(separator: " | ")))\(optionality)"
-    case .collection(let kind, _, _):
+    case .collection(kind: let kind, _, _, _):
       return "``\(kind.syntaxType)``"
     case .token(let choices, _, _):
       if choices.count == 1 {

CodeGeneration/Sources/SyntaxSupport/Node.swift

@@ -345,7 +345,7 @@ fileprivate extension Child {
       return [kind]
     case .nodeChoices(let choices):
       return choices.flatMap(\.kinds)
-    case .collection(let kind, _, _):
+    case .collection(kind: let kind, _, _, _):
       return [kind]
     case .token:
       return [.token]

CodeGeneration/Sources/SyntaxSupport/Traits.swift

@@ -69,7 +69,7 @@ public let TRAITS: [Trait] = [
       Child(name: "ArgumentList", kind: .node(kind: .labeledExprList)),
       Child(name: "RightParen", kind: .token(choices: [.token(.rightParen)]), isOptional: true),
       Child(name: "TrailingClosure", kind: .node(kind: .closureExpr), isOptional: true),
-      Child(name: "AdditionalTrailingClosures", kind: .node(kind: .multipleTrailingClosureElementList), isOptional: true),
+      Child(name: "AdditionalTrailingClosures", kind: .node(kind: .multipleTrailingClosureElementList)),
     ]
   ),
   Trait(

CodeGeneration/Sources/Utils/SyntaxBuildableChild.swift

@@ -33,7 +33,7 @@ public extension Child {
       buildableKind = .node(kind: kind)
     case .nodeChoices:
       buildableKind = .node(kind: .syntax)
-    case .collection(let kind, _, _):
+    case .collection(kind: let kind, _, _, _):
       buildableKind = .node(kind: kind)
     case .token:
       buildableKind = .token(self.tokenKind!)
@@ -65,6 +65,9 @@ public extension Child {
         return ExprSyntax("nil")
       }
     }
+    if case .collection(_, _, defaultsToEmpty: true, _) = kind {
+      return ExprSyntax("[]")
+    }
     guard let token = token, isToken else {
       return type.defaultValue
     }

CodeGeneration/Sources/generate-swiftsyntax/templates/swiftsyntax/RenamedChildrenCompatibilityFile.swift

@@ -38,7 +38,8 @@ let renamedChildrenCompatibilityFile = try! SourceFileSyntax(leadingTrivia: copy
           )
           if let childNode = SYNTAX_NODE_MAP[child.syntaxNodeKind]?.collectionNode,
             !child.isUnexpectedNodes,
-            case .collection(_, let collectionElementName, let deprecatedCollectionElementName) = child.kind,
+            case .collection(_, collectionElementName: let collectionElementName, _, deprecatedCollectionElementName: let deprecatedCollectionElementName) =
+              child.kind,
             let deprecatedCollectionElementName
           {
             let childEltType = childNode.collectionElementType.syntaxBaseName

CodeGeneration/Sources/generate-swiftsyntax/templates/swiftsyntax/SyntaxNodesFile.swift

@@ -192,7 +192,7 @@ func syntaxNode(emitKind: SyntaxNodeKind) -> SourceFileSyntax {
           // If needed, this could be added in the future, but for now withUnexpected should be sufficient.
           if let childNode = SYNTAX_NODE_MAP[child.syntaxNodeKind]?.collectionNode,
             !child.isUnexpectedNodes,
-            case .collection(_, let childElt, _) = child.kind
+            case .collection(_, collectionElementName: let childElt, _, _) = child.kind
           {
             let childEltType = childNode.collectionElementType.syntaxBaseName
 

CodeGeneration/Tests/ValidateSyntaxNodes/ValidateSyntaxNodes.swift

@@ -56,13 +56,13 @@ fileprivate extension ChildKind {
       return kind == otherKind
     case (.nodeChoices(let choices), .nodeChoices(let otherChoices)):
       return choices.count == otherChoices.count && zip(choices, otherChoices).allSatisfy { $0.hasSameType(as: $1) }
-    case (.collection(let kind, _, _), .collection(let otherKind, _, _)):
+    case (.collection(kind: let kind, _, _, _), .collection(kind: let otherKind, _, _, _)):
       return kind == otherKind
     case (.token(let choices, _, _), .token(let otherChoices, _, _)):
       return choices == otherChoices
-    case (.node(let kind), .collection(let otherKind, _, _)):
+    case (.node(let kind), .collection(kind: let otherKind, _, _, _)):
       return kind == otherKind
-    case (.collection(let kind, _, _), .node(let otherKind)):
+    case (.collection(kind: let kind, _, _, _), .node(let otherKind)):
       return kind == otherKind
     default:
       return false