Allow postfix #if to be empty

CodeGeneration/Sources/SyntaxSupport/gyb_generated/DeclNodes.swift

@@ -183,6 +183,7 @@ public let DECL_NODES: [Node] = [
                classification: "BuildConfigId"),
          Child(name: "Elements",
                kind: "Syntax",
+               isOptional: true,
                nodeChoices: [
                  Child(name: "Statements",
                        kind: "CodeBlockItemList"),

Sources/SwiftBasicFormat/generated/BasicFormat.swift

@@ -934,7 +934,7 @@ open class BasicFormat: SyntaxRewriter {
     let unexpectedBetweenPoundKeywordAndCondition = node.unexpectedBetweenPoundKeywordAndCondition.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
     let condition = node.condition.map(self.visit)?.cast(ExprSyntax.self)
     let unexpectedBetweenConditionAndElements = node.unexpectedBetweenConditionAndElements.map(self.visit)?.cast(UnexpectedNodesSyntax.self)
-    let elements = self.visit(node.elements).cast(Syntax.self)
+    let elements = node.elements.map(self.visit)?.cast(Syntax.self)
     return Syntax(IfConfigClauseSyntax(unexpectedBeforePoundKeyword, poundKeyword: poundKeyword, unexpectedBetweenPoundKeywordAndCondition, condition: condition, unexpectedBetweenConditionAndElements, elements: elements))
   }
 

Sources/SwiftParser/Directives.swift

@@ -68,7 +68,7 @@ extension Parser {
   public mutating func parsePoundIfDirective<Element: RawSyntaxNodeProtocol>(
     _ parseElement: (inout Parser) -> Element?,
     addSemicolonIfNeeded: (_ lastElement: Element, _ newItemAtStartOfLine: Bool, _ parser: inout Parser) -> Element? = { _, _, _ in nil },
-    syntax: (inout Parser, [Element]) -> RawSyntax
+    syntax: (inout Parser, [Element]) -> RawSyntax?
   ) -> RawIfConfigDeclSyntax {
     var clauses = [RawIfConfigClauseSyntax]()
     do {

Sources/SwiftParser/Expressions.swift

@@ -592,13 +592,13 @@ extension Parser {
       // TODO: diagnose and skip the remaining token in the current clause.
       return result
     }
-  syntax: { parser, elements in
-      guard elements.count == 1 else {
-        assert(elements.isEmpty)
-        return RawSyntax(RawMissingExprSyntax(arena: parser.arena))
-      }
-      return RawSyntax(elements.first!)
+  syntax: { (parser, elements) -> RawSyntax? in
+    switch elements.count {
+    case 0: return nil
+    case 1: return RawSyntax(elements.first!)
+    default: fatalError("Postfix #if should only have one element")
     }
+  }
 
     return RawExprSyntax(RawPostfixIfConfigExprSyntax(
       base: start, config: config,

Sources/SwiftSyntax/Raw/gyb_generated/RawSyntaxNodes.swift

@@ -7952,7 +7952,7 @@ public struct RawIfConfigClauseSyntax: RawSyntaxNodeProtocol, RawSyntaxToSyntax
     _ unexpectedBetweenPoundKeywordAndCondition: RawUnexpectedNodesSyntax? = nil,
     condition: RawExprSyntax?,
     _ unexpectedBetweenConditionAndElements: RawUnexpectedNodesSyntax? = nil,
-    elements: RawSyntax,
+    elements: RawSyntax?,
     _ unexpectedAfterElements: RawUnexpectedNodesSyntax? = nil,
     arena: __shared SyntaxArena
   ) {
@@ -7964,7 +7964,7 @@ public struct RawIfConfigClauseSyntax: RawSyntaxNodeProtocol, RawSyntaxToSyntax
       layout[2] = unexpectedBetweenPoundKeywordAndCondition?.raw
       layout[3] = condition?.raw
       layout[4] = unexpectedBetweenConditionAndElements?.raw
-      layout[5] = elements.raw
+      layout[5] = elements?.raw
       layout[6] = unexpectedAfterElements?.raw
     }
     self.init(raw: raw)
@@ -8000,11 +8000,11 @@ public struct RawIfConfigClauseSyntax: RawSyntaxNodeProtocol, RawSyntaxToSyntax
   public func withUnexpectedBetweenConditionAndElements(_ unexpectedBetweenConditionAndElements: RawUnexpectedNodesSyntax?, arena: SyntaxArena) -> RawIfConfigClauseSyntax {
     return layoutView.replacingChild(at: 4, with: unexpectedBetweenConditionAndElements.map(RawSyntax.init), arena: arena).as(RawIfConfigClauseSyntax.self)!
   }
-  public var elements: RawSyntax {
-    layoutView.children[5]!
+  public var elements: RawSyntax? {
+    layoutView.children[5]
   }
-  public func withElements(_ elements: RawSyntax, arena: SyntaxArena) -> RawIfConfigClauseSyntax {
-    return layoutView.replacingChild(at: 5, with: RawSyntax(elements), arena: arena).as(RawIfConfigClauseSyntax.self)!
+  public func withElements(_ elements: RawSyntax?, arena: SyntaxArena) -> RawIfConfigClauseSyntax {
+    return layoutView.replacingChild(at: 5, with: elements.map(RawSyntax.init), arena: arena).as(RawIfConfigClauseSyntax.self)!
   }
   public var unexpectedAfterElements: RawUnexpectedNodesSyntax? {
     layoutView.children[6].map(RawUnexpectedNodesSyntax.init(raw:))

Sources/SwiftSyntax/Raw/gyb_generated/RawSyntaxValidation.swift

@@ -884,7 +884,7 @@ func validateLayout(layout: RawSyntaxBuffer, as kind: SyntaxKind) {
     _verify(layout[2], as: RawUnexpectedNodesSyntax?.self)
     _verify(layout[3], as: RawExprSyntax?.self)
     _verify(layout[4], as: RawUnexpectedNodesSyntax?.self)
-    _verify(layout[5], as: RawSyntax.self)
+    _verify(layout[5], as: RawSyntax?.self)
     _verify(layout[6], as: RawUnexpectedNodesSyntax?.self)
     break
   case .ifConfigClauseList:

Sources/SwiftSyntax/gyb_generated/SyntaxFactory.swift

@@ -2752,14 +2752,14 @@ public enum SyntaxFactory {
     return FunctionSignatureSyntax(data)
   }
   @available(*, deprecated, message: "Use initializer on IfConfigClauseSyntax")
-  public static func makeIfConfigClause(_ unexpectedBeforePoundKeyword: UnexpectedNodesSyntax? = nil, poundKeyword: TokenSyntax, _ unexpectedBetweenPoundKeywordAndCondition: UnexpectedNodesSyntax? = nil, condition: ExprSyntax?, _ unexpectedBetweenConditionAndElements: UnexpectedNodesSyntax? = nil, elements: Syntax, _ unexpectedAfterElements: UnexpectedNodesSyntax? = nil) -> IfConfigClauseSyntax {
+  public static func makeIfConfigClause(_ unexpectedBeforePoundKeyword: UnexpectedNodesSyntax? = nil, poundKeyword: TokenSyntax, _ unexpectedBetweenPoundKeywordAndCondition: UnexpectedNodesSyntax? = nil, condition: ExprSyntax?, _ unexpectedBetweenConditionAndElements: UnexpectedNodesSyntax? = nil, elements: Syntax?, _ unexpectedAfterElements: UnexpectedNodesSyntax? = nil) -> IfConfigClauseSyntax {
     let layout: [RawSyntax?] = [
       unexpectedBeforePoundKeyword?.raw,
       poundKeyword.raw,
       unexpectedBetweenPoundKeywordAndCondition?.raw,
       condition?.raw,
       unexpectedBetweenConditionAndElements?.raw,
-      elements.raw,
+      elements?.raw,
       unexpectedAfterElements?.raw,
     ]
     let raw = RawSyntax.makeLayout(kind: SyntaxKind.ifConfigClause,
@@ -2777,7 +2777,7 @@ public enum SyntaxFactory {
       nil,
       nil,
       nil,
-      RawSyntax.makeEmptyLayout(kind: SyntaxKind.unknown, arena: .default),
+      nil,
       nil,
     ], arena: .default))
     return IfConfigClauseSyntax(data)

Sources/SwiftSyntax/gyb_generated/syntax_nodes/SyntaxNodes.swift

@@ -5589,7 +5589,7 @@ public struct IfConfigClauseSyntax: SyntaxProtocol, SyntaxHashable {
     _ unexpectedBetweenPoundKeywordAndCondition: UnexpectedNodesSyntax? = nil,
     condition: ExprSyntax?,
     _ unexpectedBetweenConditionAndElements: UnexpectedNodesSyntax? = nil,
-    elements: Syntax,
+    elements: Syntax?,
     _ unexpectedAfterElements: UnexpectedNodesSyntax? = nil
   ) {
     let layout: [RawSyntax?] = [
@@ -5598,7 +5598,7 @@ public struct IfConfigClauseSyntax: SyntaxProtocol, SyntaxHashable {
       unexpectedBetweenPoundKeywordAndCondition?.raw,
       condition?.raw,
       unexpectedBetweenConditionAndElements?.raw,
-      elements.raw,
+      elements?.raw,
       unexpectedAfterElements?.raw,
     ]
     let raw = RawSyntax.makeLayout(kind: SyntaxKind.ifConfigClause,
@@ -5711,9 +5711,10 @@ public struct IfConfigClauseSyntax: SyntaxProtocol, SyntaxHashable {
     return IfConfigClauseSyntax(newData)
   }
 
-  public var elements: Syntax {
+  public var elements: Syntax? {
     get {
       let childData = data.child(at: 5, parent: Syntax(self))
+      if childData == nil { return nil }
       return Syntax(childData!)
     }
     set(value) {
@@ -5726,7 +5727,7 @@ public struct IfConfigClauseSyntax: SyntaxProtocol, SyntaxHashable {
   ///                   current `elements`, if present.
   public func withElements(
     _ newChild: Syntax?) -> IfConfigClauseSyntax {
-    let raw = newChild?.raw ?? RawSyntax.makeEmptyLayout(kind: SyntaxKind.unknown, arena: .default)
+    let raw = newChild?.raw
     let newData = data.replacingChild(raw, at: 5)
     return IfConfigClauseSyntax(newData)
   }
@@ -5782,7 +5783,7 @@ extension IfConfigClauseSyntax: CustomReflectable {
       "unexpectedBetweenPoundKeywordAndCondition": unexpectedBetweenPoundKeywordAndCondition.map(Syntax.init)?.asProtocol(SyntaxProtocol.self) as Any,
       "condition": condition.map(Syntax.init)?.asProtocol(SyntaxProtocol.self) as Any,
       "unexpectedBetweenConditionAndElements": unexpectedBetweenConditionAndElements.map(Syntax.init)?.asProtocol(SyntaxProtocol.self) as Any,
-      "elements": Syntax(elements).asProtocol(SyntaxProtocol.self),
+      "elements": elements.map(Syntax.init)?.asProtocol(SyntaxProtocol.self) as Any,
       "unexpectedAfterElements": unexpectedAfterElements.map(Syntax.init)?.asProtocol(SyntaxProtocol.self) as Any,
     ])
   }

Sources/SwiftSyntaxBuilder/generated/BuildableNodes.swift

@@ -7999,7 +7999,7 @@ public struct IfConfigClause: SyntaxBuildable, ExpressibleAsIfConfigClause {
     var unexpectedBetweenPoundKeywordAndCondition: UnexpectedNodes?
     var condition: ExprBuildable?
     var unexpectedBetweenConditionAndElements: UnexpectedNodes?
-    var elements: SyntaxBuildable
+    var elements: SyntaxBuildable?
   }
   enum Data {
     case buildable(BuildableData)
@@ -8014,9 +8014,9 @@ public struct IfConfigClause: SyntaxBuildable, ExpressibleAsIfConfigClause {
   ///   - condition: 
   ///   - unexpectedBetweenConditionAndElements: 
   ///   - elements: 
-  public init (leadingTrivia: Trivia = [], trailingTrivia: Trivia = [], unexpectedBeforePoundKeyword: ExpressibleAsUnexpectedNodes? = nil, poundKeyword: Token, unexpectedBetweenPoundKeywordAndCondition: ExpressibleAsUnexpectedNodes? = nil, condition: ExpressibleAsExprBuildable? = nil, unexpectedBetweenConditionAndElements: ExpressibleAsUnexpectedNodes? = nil, elements: ExpressibleAsSyntaxBuildable) {
+  public init (leadingTrivia: Trivia = [], trailingTrivia: Trivia = [], unexpectedBeforePoundKeyword: ExpressibleAsUnexpectedNodes? = nil, poundKeyword: Token, unexpectedBetweenPoundKeywordAndCondition: ExpressibleAsUnexpectedNodes? = nil, condition: ExpressibleAsExprBuildable? = nil, unexpectedBetweenConditionAndElements: ExpressibleAsUnexpectedNodes? = nil, elements: ExpressibleAsSyntaxBuildable? = nil) {
     assert(poundKeyword.text == #"#if"# || poundKeyword.text == #"#elseif"# || poundKeyword.text == #"#else"#)
-    self.data = .buildable(BuildableData(leadingTrivia: leadingTrivia, trailingTrivia: trailingTrivia, unexpectedBeforePoundKeyword: unexpectedBeforePoundKeyword?.createUnexpectedNodes(), poundKeyword: poundKeyword, unexpectedBetweenPoundKeywordAndCondition: unexpectedBetweenPoundKeywordAndCondition?.createUnexpectedNodes(), condition: condition?.createExprBuildable(), unexpectedBetweenConditionAndElements: unexpectedBetweenConditionAndElements?.createUnexpectedNodes(), elements: elements.createSyntaxBuildable()))
+    self.data = .buildable(BuildableData(leadingTrivia: leadingTrivia, trailingTrivia: trailingTrivia, unexpectedBeforePoundKeyword: unexpectedBeforePoundKeyword?.createUnexpectedNodes(), poundKeyword: poundKeyword, unexpectedBetweenPoundKeywordAndCondition: unexpectedBetweenPoundKeywordAndCondition?.createUnexpectedNodes(), condition: condition?.createExprBuildable(), unexpectedBetweenConditionAndElements: unexpectedBetweenConditionAndElements?.createUnexpectedNodes(), elements: elements?.createSyntaxBuildable()))
   }
   public init(_ constructedNode: IfConfigClauseSyntax) {
     self.data = .constructed(constructedNode)
@@ -8027,7 +8027,7 @@ public struct IfConfigClause: SyntaxBuildable, ExpressibleAsIfConfigClause {
   func buildIfConfigClause() -> IfConfigClauseSyntax {
     switch data {
     case .buildable(let buildableData): 
-      var result = IfConfigClauseSyntax(buildableData.unexpectedBeforePoundKeyword?.buildUnexpectedNodes(), poundKeyword: buildableData.poundKeyword.buildToken(), buildableData.unexpectedBetweenPoundKeywordAndCondition?.buildUnexpectedNodes(), condition: buildableData.condition?.buildExpr(), buildableData.unexpectedBetweenConditionAndElements?.buildUnexpectedNodes(), elements: buildableData.elements.buildSyntax())
+      var result = IfConfigClauseSyntax(buildableData.unexpectedBeforePoundKeyword?.buildUnexpectedNodes(), poundKeyword: buildableData.poundKeyword.buildToken(), buildableData.unexpectedBetweenPoundKeywordAndCondition?.buildUnexpectedNodes(), condition: buildableData.condition?.buildExpr(), buildableData.unexpectedBetweenConditionAndElements?.buildUnexpectedNodes(), elements: buildableData.elements?.buildSyntax())
       result.leadingTrivia = buildableData.leadingTrivia + (result.leadingTrivia ?? [])
       result.trailingTrivia = buildableData.trailingTrivia + (result.trailingTrivia ?? [])
       return result

Sources/SwiftSyntaxParser/gyb_generated/NodeDeclarationHash.swift

@@ -17,6 +17,6 @@
 extension SyntaxParser {
   static func verifyNodeDeclarationHash() -> Bool {
     return String(cString: swiftparse_syntax_structure_versioning_identifier()!) ==
-      "82461208aad7b9c2a13fb8715fdddce431fa2f3f"
+      "2a5be09fdaf9642a740c7436fd887ffa1251fa7b"
   }
 }

Tests/SwiftParserTest/translated/IfconfigExprTests.swift

@@ -93,9 +93,7 @@ final class IfconfigExprTests: XCTestCase {
       }
       """#,
       diagnostics: [
-        // TODO: Old parser expected error on line 8: unary operator cannot be separated from its operand
         DiagnosticSpec(locationMarker: "1️⃣", message: "unexpected code '+ otherExpr' in conditional compilation block"),
-        // TODO: Old parser expected error on line 13: unexpected tokens in '#if' expression body
         DiagnosticSpec(locationMarker: "2️⃣", message: #"unexpected code 'print("debug")' in conditional compilation block"#),
       ]
     )
@@ -120,7 +118,6 @@ final class IfconfigExprTests: XCTestCase {
       }
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 12: unexpected tokens in '#if' expression body
         DiagnosticSpec(message: "unexpected code '+ 12' in conditional compilation block"),
       ]
     )
@@ -133,22 +130,19 @@ final class IfconfigExprTests: XCTestCase {
         baseExpr
       #if CONDITION_1
           .methodOne() 
-      #elseif CONDITION_21️⃣
+      #elseif CONDITION_2
           // OK. Do nothing.
       #endif
         baseExpr
       #if CONDITION_1
           .methodOne() 
-      #elseif CONDITION_22️⃣
-        3️⃣return         
+      #elseif CONDITION_2
+        1️⃣return         
       #endif
       }
       """,
       diagnostics: [
-        DiagnosticSpec(locationMarker: "1️⃣", message: "expected expression in conditional compilation clause"),
-        DiagnosticSpec(locationMarker: "2️⃣", message: "expected expression in conditional compilation clause"),
-        // TODO: Old parser expected error on line 12: unexpected tokens in '#if' expression body
-        DiagnosticSpec(locationMarker: "3️⃣", message: "unexpected code 'return' in conditional compilation block"),
+        DiagnosticSpec(message: "unexpected code 'return' in conditional compilation block"),
       ]
     )
   }

Tests/SwiftParserTest/translated/ImplicitGetterIncompleteTests.swift

@@ -27,10 +27,8 @@ final class ImplicitGetterIncompleteTests: XCTestCase {
         var a : Int { 
           switch i { 
       }1️⃣
-      // expected-error@+1 2 {{expected '}'}}
       """#,
       diagnostics: [
-        // TODO: Old parser expected error on line 4: 'switch' statement body must have at least one 'case'
         DiagnosticSpec(message: "expected '}' to end variable"),
         DiagnosticSpec(message: "expected '}' to end function"),
       ]

gyb_syntax_support/DeclNodes.py

@@ -102,7 +102,7 @@
                    ]),
              Child('Condition', kind='Expr', name_for_diagnostics='condition', classification='BuildConfigId',
                    is_optional=True),
-             Child('Elements', kind='Syntax',
+             Child('Elements', is_optional=True, kind='Syntax',
                    node_choices=[
                        Child('Statements', kind='CodeBlockItemList'),
                        Child('SwitchCases', kind='SwitchCaseList'),