swiftlang · ahoppen · Apr 22, 2023 · Apr 21, 2023 · Apr 21, 2023 · Apr 21, 2023
@@ -144,6 +144,7 @@ public let COMMON_NODES: [Node] = [
   Node(
     name: "MissingDecl",
     nameForDiagnostics: "declaration",
+    description: "In case the source code is missing a declaration, this node stands in place of the missing declaration.",
     kind: "Decl",
     traits: [
       "Attributed"
@@ -152,44 +153,108 @@ public let COMMON_NODES: [Node] = [
       Child(
         name: "Attributes",
         kind: .collection(kind: "AttributeList", collectionElementName: "Attribute"),
+        description: "If there were standalone attributes without a declaration to attach them to, the `MissingDeclSyntax` will contain these.",
         isOptional: true
       ),
       Child(
         name: "Modifiers",
         kind: .collection(kind: "ModifierList", collectionElementName: "Modifier"),
+        description: "If there were standalone modifiers without a declaration to attach them to, the `MissingDeclSyntax` will contain these.",
         isOptional: true
       ),
+      Child(
+        name: "Placeholder",
+        kind: .token(choices: [.token(tokenKind: "IdentifierToken")], requiresLeadingSpace: false, requiresTrailingSpace: false),
+        description: """
+          A placeholder, i.e. `<#decl#>` that can be inserted into the source code to represent the missing declaration.
+          This token should always have `presence = .missing`.
+          """
+      ),
     ]
   ),
 
   Node(
     name: "MissingExpr",
     nameForDiagnostics: "expression",
-    kind: "Expr"
+    description: "In case the source code is missing a expression, this node stands in place of the missing expression.",
+    kind: "Expr",
+    children: [
+      Child(
+        name: "Placeholder",
+        kind: .token(choices: [.token(tokenKind: "IdentifierToken")], requiresLeadingSpace: false, requiresTrailingSpace: false),
+        description: """
+          A placeholder, i.e. `<#expression#>` that can be inserted into the source code to represent the missing expression.
+          This token should always have `presence = .missing`.
+          """
+      )
+    ]
   ),
 
   Node(
     name: "MissingPattern",
     nameForDiagnostics: "pattern",
-    kind: "Pattern"
+    description: "In case the source code is missing a pattern, this node stands in place of the missing pattern.",
+    kind: "Pattern",
+    children: [
+      Child(
+        name: "Placeholder",
+        kind: .token(choices: [.token(tokenKind: "IdentifierToken")], requiresLeadingSpace: false, requiresTrailingSpace: false),
+        description: """
+          A placeholder, i.e. `<#pattern#>` that can be inserted into the source code to represent the missing pattern.
+          This token should always have `presence = .missing`.
+          """
+      )
+    ]
   ),
 
   Node(
     name: "MissingStmt",
     nameForDiagnostics: "statement",
-    kind: "Stmt"
+    description: "In case the source code is missing a statement, this node stands in place of the missing statement.",
+    kind: "Stmt",
+    children: [
+      Child(
+        name: "Placeholder",
+        kind: .token(choices: [.token(tokenKind: "IdentifierToken")], requiresLeadingSpace: false, requiresTrailingSpace: false),
+        description: """
+          A placeholder, i.e. `<#statement#>` that can be inserted into the source code to represent the missing pattern.
+          This token should always have `presence = .missing`.
+          """
+      )
+    ]
   ),
 
   Node(
     name: "Missing",
     nameForDiagnostics: nil,
-    kind: "Syntax"
+    description: "In case the source code is missing a syntax node, this node stands in place of the missing node.",
+    kind: "Syntax",
+    children: [
+      Child(
+        name: "Placeholder",
+        kind: .token(choices: [.token(tokenKind: "IdentifierToken")], requiresLeadingSpace: false, requiresTrailingSpace: false),
+        description: """
+          A placeholder, i.e. `<#syntax#>` that can be inserted into the source code to represent the missing pattern.
+          This token should always have `presence = .missing`
+          """
+      )
+    ]
   ),
 
   Node(
     name: "MissingType",
     nameForDiagnostics: "type",
-    kind: "Type"
+    description: "In case the source code is missing a type, this node stands in place of the missing type.",
+    kind: "Type",
+    children: [
+      Child(
+        name: "Placeholder",
+        kind: .token(choices: [.token(tokenKind: "IdentifierToken")], requiresLeadingSpace: false, requiresTrailingSpace: false),
+        description: """
+          A placeholder, i.e. `<#type#>` that can be inserted into the source code to represent the missing type. This token should always have `presence = .missing`.
+          """
+      )
+    ]
   ),
 
   Node(

@@ -15,6 +15,18 @@ import SwiftSyntaxBuilder
 import SyntaxSupport
 import Utils
 
+extension Child {
+  public var docComment: SwiftSyntax.Trivia {
+    guard let description = description else {
+      return []
+    }
+    let dedented = dedented(string: description)
+    let lines = dedented.split(separator: "\n", omittingEmptySubsequences: false)
+    let pieces = lines.map { SwiftSyntax.TriviaPiece.docLineComment("/// \($0)") }
+    return Trivia(pieces: pieces)
+  }
+}
+
 /// This file generates the syntax nodes for SwiftSyntax. To keep the generated
 /// files at a managable file size, it is to be invoked multiple times with the
 /// variable `emitKind` set to a base kind listed in
@@ -33,7 +45,7 @@ func syntaxNode(emitKind: String) -> SourceFileSyntax {
         """
       ) {
         for child in node.children {
-          if let childChoiceDecl = try generateSyntaxChildChoices(for: child) {
+          if let childChoiceDecl = try! generateSyntaxChildChoices(for: child) {
             childChoiceDecl
           }
         }
@@ -140,7 +152,7 @@ func syntaxNode(emitKind: String) -> SourceFileSyntax {
         if node.hasOptionalBaseTypeChild {
           // TODO: Remove when we no longer support compiling in Swift 5.6. Change the
           // above constructor to use `Optional<BaseType>.none` instead.
-          try InitializerDeclSyntax(
+          try! InitializerDeclSyntax(
             """
             /// This initializer exists solely because Swift 5.6 does not support
             /// `Optional<ConcreteType>.none` as a default value of a generic parameter.
@@ -191,11 +203,10 @@ func syntaxNode(emitKind: String) -> SourceFileSyntax {
 
           let childType: String = child.kind.isNodeChoicesEmpty ? child.typeName : child.name
           let type = child.isOptional ? TypeSyntax("\(raw: childType)?") : TypeSyntax("\(raw: childType)")
-          let childDoc = child.description.map { dedented(string: $0) }.map { Trivia.docLineComment("/// \($0)") }
 
-          try VariableDeclSyntax(
+          try! VariableDeclSyntax(
             """
-            \(raw: childDoc ?? [])
+            \(raw: child.docComment)
             public var \(raw: child.swiftName): \(type)
             """
           ) {
@@ -274,7 +285,7 @@ private func generateSyntaxChildChoices(for child: Child) throws -> EnumDeclSynt
     return nil
   }
 
-  return try EnumDeclSyntax("public enum \(raw: child.name): SyntaxChildChoices") {
+  return try! EnumDeclSyntax("public enum \(raw: child.name): SyntaxChildChoices") {
     for choice in choices {
       DeclSyntax("case `\(raw: choice.swiftName)`(\(raw: choice.typeName))")
     }

@@ -335,5 +335,17 @@ let syntaxRewriterFile = SourceFileSyntax(leadingTrivia: copyrightHeader) {
       }
       """
     )
+
+    DeclSyntax(
+      """
+      /// Rewrite `node` and anchor, making sure that the rewritten node also has
+      /// a parent if `node` had one.
+      public func rewrite(_ node: Syntax) -> Syntax {
+        let rewritten = self.visit(node)
+        let arena = SyntaxArena()
+        return Syntax(node.data.replacingSelf(rewritten.raw, arena: arena))
+      }
+      """
+    )
   }
 }
@@ -245,6 +245,18 @@ fileprivate extension AnyKeyPath {
       return false
     case \FunctionParameterSyntax.secondName:
       return true
+    case \MissingDeclSyntax.placeholder:
+      return false
+    case \MissingExprSyntax.placeholder:
+      return false
+    case \MissingPatternSyntax.placeholder:
+      return false
+    case \MissingStmtSyntax.placeholder:
+      return false
+    case \MissingSyntax.placeholder:
+      return false
+    case \MissingTypeSyntax.placeholder:
+      return false
     default:
       return nil
     }
@@ -262,6 +274,18 @@ fileprivate extension AnyKeyPath {
       return false
     case \DynamicReplacementArgumentsSyntax.forLabel:
       return false
+    case \MissingDeclSyntax.placeholder:
+      return false
+    case \MissingExprSyntax.placeholder:
+      return false
+    case \MissingPatternSyntax.placeholder:
+      return false
+    case \MissingStmtSyntax.placeholder:
+      return false
+    case \MissingSyntax.placeholder:
+      return false
+    case \MissingTypeSyntax.placeholder:
+      return false
     case \SwitchCaseLabelSyntax.colon:
       return false
     case \SwitchDefaultLabelSyntax.colon:

@@ -335,17 +335,18 @@ extension ParseDiagnosticsGenerator {
 
     /// Ancestors that don't contain any tokens are not very interesting to merge diagnostics (because there can't be any missing tokens we can merge them with).
     /// Find the first ancestor that contains any tokens.
-    var ancestorWithTokens = node.parent
+    var ancestorWithMoreTokens = node.parent
     var index = node.index
-    while let unwrappedParent = ancestorWithTokens, !unwrappedParent.hasTokens {
-      ancestorWithTokens = unwrappedParent.parent
+    let nodeTokens = Array(node.tokens(viewMode: .all))
+    while let unwrappedParent = ancestorWithMoreTokens, Array(unwrappedParent.tokens(viewMode: .all)) == nodeTokens {
+      ancestorWithMoreTokens = unwrappedParent.parent
       index = unwrappedParent.index
     }
 
     // Walk all upcoming sibling to see if they are also missing to handle them in this diagnostic.
     // If this is the case, handle all of them in this diagnostic.
     var missingNodes = [Syntax(node)]
-    if let parentWithTokens = ancestorWithTokens {
+    if let parentWithTokens = ancestorWithMoreTokens {
       let siblings = parentWithTokens.children(viewMode: .all)
       let siblingsAfter = siblings[siblings.index(after: index)...]
       for sibling in siblingsAfter {

@@ -953,27 +953,27 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
   }
 
   public override func visit(_ node: MissingDeclSyntax) -> SyntaxVisitorContinueKind {
-    return handleMissingSyntax(node)
+    return handleMissingSyntax(node, additionalHandledNodes: [node.placeholder.id])
   }
 
   public override func visit(_ node: MissingExprSyntax) -> SyntaxVisitorContinueKind {
-    return handleMissingSyntax(node)
+    return handleMissingSyntax(node, additionalHandledNodes: [node.placeholder.id])
   }
 
   public override func visit(_ node: MissingPatternSyntax) -> SyntaxVisitorContinueKind {
-    return handleMissingSyntax(node)
+    return handleMissingSyntax(node, additionalHandledNodes: [node.placeholder.id])
   }
 
   public override func visit(_ node: MissingStmtSyntax) -> SyntaxVisitorContinueKind {
-    return handleMissingSyntax(node)
+    return handleMissingSyntax(node, additionalHandledNodes: [node.placeholder.id])
   }
 
   public override func visit(_ node: MissingSyntax) -> SyntaxVisitorContinueKind {
-    return handleMissingSyntax(node)
+    return handleMissingSyntax(node, additionalHandledNodes: [node.placeholder.id])
   }
 
   public override func visit(_ node: MissingTypeSyntax) -> SyntaxVisitorContinueKind {
-    return handleMissingSyntax(node)
+    return handleMissingSyntax(node, additionalHandledNodes: [node.placeholder.id])
   }
 
   public override func visit(_ node: OperatorDeclSyntax) -> SyntaxVisitorContinueKind {

@@ -60,62 +60,6 @@ class PresentMaker: SyntaxRewriter {
       return token
     }
   }
-
-  override func visit(_ node: MissingDeclSyntax) -> DeclSyntax {
-    let leadingTriviaBeforePlaceholder: Trivia
-    if node.isMissingAllTokens {
-      leadingTriviaBeforePlaceholder = []
-    } else if node.modifiers != nil {
-      leadingTriviaBeforePlaceholder = .space
-    } else {
-      leadingTriviaBeforePlaceholder = .newline
-    }
-    return DeclSyntax(
-      StructDeclSyntax(
-        node.unexpectedBeforeAttributes,
-        attributes: node.attributes,
-        node.unexpectedBetweenAttributesAndModifiers,
-        modifiers: node.modifiers,
-        structKeyword: .keyword(.struct, presence: .missing),
-        identifier: .identifier("<#declaration#>", leadingTrivia: leadingTriviaBeforePlaceholder),
-        memberBlock: MemberDeclBlockSyntax(
-          leftBrace: .leftBraceToken(presence: .missing),
-          members: MemberDeclListSyntax([]),
-          rightBrace: .rightBraceToken(presence: .missing)
-        )
-      )
-    )
-  }
-
-  override func visit(_ node: MissingExprSyntax) -> ExprSyntax {
-    return ExprSyntax(IdentifierExprSyntax(identifier: .identifier("<#expression#>")))
-  }
-
-  override func visit(_ node: MissingPatternSyntax) -> PatternSyntax {
-    return PatternSyntax(IdentifierPatternSyntax(identifier: .identifier("<#pattern#>")))
-  }
-
-  override func visit(_ node: MissingStmtSyntax) -> StmtSyntax {
-    return StmtSyntax(
-      DoStmtSyntax(
-        doKeyword: .keyword(.do, presence: .missing),
-        UnexpectedNodesSyntax([Syntax(TokenSyntax.identifier("<#statement#>"))]),
-        body: CodeBlockSyntax(
-          leftBrace: .leftBraceToken(presence: .missing),
-          statements: CodeBlockItemListSyntax([]),
-          rightBrace: .rightBraceToken(presence: .missing)
-        )
-      )
-    )
-  }
-
-  override func visit(_ node: MissingTypeSyntax) -> TypeSyntax {
-    return TypeSyntax(SimpleTypeIdentifierSyntax(name: .identifier("<#type#>")))
-  }
-
-  override func visit(_ node: MissingSyntax) -> Syntax {
-    return Syntax(IdentifierExprSyntax(identifier: .identifier("<#syntax#>")))
-  }
 }
 
 class MissingMaker: SyntaxRewriter {

@@ -12,6 +12,8 @@ add_swift_host_library(SwiftSyntax
   BumpPtrAllocator.swift
   CommonAncestor.swift
   IncrementalParseTransition.swift
+  MemoryLayout.swift
+  MissingNodeInitializers.swift
   Trivia.swift
   SourceLength.swift
   SourceLocation.swift