Add editor place holder pattern

Author: kimdv

CodeGeneration/Sources/SyntaxSupport/PatternNodes.swift

@@ -182,4 +182,22 @@ public let PATTERN_NODES: [Node] = [
     ]
   ),
 
+  Node(
+    kind: .editorPlaceholderPattern,
+    base: .pattern,
+    nameForDiagnostics: "editor placeholder",
+    documentation: """
+      An editor placeholder, e.g. `<#pattern#>` that is used in a position that expects a pattern.
+      """,
+    children: [
+      Child(
+        name: "placeholder",
+        kind: .token(choices: [.token(.identifier)]),
+        documentation: """
+          The actual editor placeholder that starts with `<#` and ends with `#>`.
+          """
+      )
+    ]
+  ),
+
 ]

CodeGeneration/Sources/SyntaxSupport/SyntaxNodeKind.swift

@@ -111,6 +111,7 @@ public enum SyntaxNodeKind: String, CaseIterable {
   case dynamicReplacementAttributeArguments
   case editorPlaceholderDecl
   case editorPlaceholderExpr
+  case editorPlaceholderPattern
   case effectsAttributeArgumentList
   case enumCaseDecl
   case enumCaseElement

Release Notes/510.md

@@ -21,6 +21,11 @@
   - Description: Remarks are used by the Swift compiler and other tools to describe some aspect of translation that doesn't reflect correctness, but may be useful for the user. Remarks have been added to the diagnostic severity enums to align with the Swift compiler.
   - Pull Request: https://github.com/apple/swift-syntax/pull/2143
 
+- New pattern node `EditorPlaceholderPatternSyntax`
+  - Description: This node type will be placeholder that is used in a position that expects a pattern.
+  - Issue: https://github.com/apple/swift-syntax/issues/2147
+  - Pull Request: https://github.com/apple/swift-syntax/pull/2150
+
 ## API Behavior Changes
 
 ## Deprecations

Sources/SwiftParser/Patterns.swift

@@ -70,12 +70,21 @@ extension Parser {
       )
     case (.lhs(.identifier), let handle)?:
       let identifier = self.eat(handle)
-      return RawPatternSyntax(
-        RawIdentifierPatternSyntax(
-          identifier: identifier,
-          arena: self.arena
+      if identifier.tokenText.isEditorPlaceholder {
+        return RawPatternSyntax(
+          RawEditorPlaceholderPatternSyntax(
+            placeholder: identifier,
+            arena: self.arena
+          )
         )
-      )
+      } else {
+        return RawPatternSyntax(
+          RawIdentifierPatternSyntax(
+            identifier: identifier,
+            arena: self.arena
+          )
+        )
+      }
     case (.lhs(.dollarIdentifier), let handle)?:
       let dollarIdent = self.eat(handle)
       let unexpectedBeforeIdentifier = RawUnexpectedNodesSyntax(elements: [RawSyntax(dollarIdent)], arena: self.arena)

Sources/SwiftParserDiagnostics/generated/SyntaxKindNameForDiagnostics.swift

@@ -143,6 +143,8 @@ extension SyntaxKind {
       return "editor placeholder"
     case .editorPlaceholderExpr:
       return "editor placeholder"
+    case .editorPlaceholderPattern:
+      return "editor placeholder"
     case .effectsAttributeArgumentList:
       return "@_effects arguments"
     case .enumCaseDecl:

Sources/SwiftSyntax/Documentation.docc/generated/SwiftSyntax.md

@@ -151,6 +151,7 @@ These articles are intended for developers wishing to contribute to SwiftSyntax
 - <doc:SwiftSyntax/PatternSyntax>
 - <doc:SwiftSyntax/PatternSyntaxProtocol>
 - <doc:SwiftSyntax/MissingPatternSyntax>
+- <doc:SwiftSyntax/EditorPlaceholderPatternSyntax>
 - <doc:SwiftSyntax/ExpressionPatternSyntax>
 - <doc:SwiftSyntax/IdentifierPatternSyntax>
 - <doc:SwiftSyntax/IsTypePatternSyntax>

Sources/SwiftSyntax/generated/ChildNameForKeyPath.swift

@@ -1077,6 +1077,12 @@ public func childName(_ keyPath: AnyKeyPath) -> String? {
     return "placeholder"
   case \EditorPlaceholderExprSyntax.unexpectedAfterPlaceholder:
     return "unexpectedAfterPlaceholder"
+  case \EditorPlaceholderPatternSyntax.unexpectedBeforePlaceholder:
+    return "unexpectedBeforePlaceholder"
+  case \EditorPlaceholderPatternSyntax.placeholder:
+    return "placeholder"
+  case \EditorPlaceholderPatternSyntax.unexpectedAfterPlaceholder:
+    return "unexpectedAfterPlaceholder"
   case \EnumCaseDeclSyntax.unexpectedBeforeAttributes:
     return "unexpectedBeforeAttributes"
   case \EnumCaseDeclSyntax.attributes:

Sources/SwiftSyntax/generated/SyntaxAnyVisitor.swift

@@ -776,6 +776,14 @@ open class SyntaxAnyVisitor: SyntaxVisitor {
     visitAnyPost(node._syntaxNode)
   }
 
+  override open func visit(_ node: EditorPlaceholderPatternSyntax) -> SyntaxVisitorContinueKind {
+    return visitAny(node._syntaxNode)
+  }
+  
+  override open func visitPost(_ node: EditorPlaceholderPatternSyntax) {
+    visitAnyPost(node._syntaxNode)
+  }
+  
   override open func visit(_ node: EffectsAttributeArgumentListSyntax) -> SyntaxVisitorContinueKind {
     return visitAny(node._syntaxNode)
   }

Sources/SwiftSyntax/generated/SyntaxBaseNodes.swift

@@ -770,7 +770,7 @@ public struct PatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
 
   public init?(_ node: some SyntaxProtocol) {
     switch node.raw.kind {
-    case .expressionPattern, .identifierPattern, .isTypePattern, .missingPattern, .tuplePattern, .valueBindingPattern, .wildcardPattern:
+    case .editorPlaceholderPattern, .expressionPattern, .identifierPattern, .isTypePattern, .missingPattern, .tuplePattern, .valueBindingPattern, .wildcardPattern:
       self._syntaxNode = node._syntaxNode
     default:
       return nil
@@ -795,6 +795,7 @@ public struct PatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
 
   public static var structure: SyntaxNodeStructure {
     return .choices([
+          .node(EditorPlaceholderPatternSyntax.self),
           .node(ExpressionPatternSyntax.self),
           .node(IdentifierPatternSyntax.self),
           .node(IsTypePatternSyntax.self),
@@ -1486,6 +1487,7 @@ extension Syntax {
           .node(DynamicReplacementAttributeArgumentsSyntax.self),
           .node(EditorPlaceholderDeclSyntax.self),
           .node(EditorPlaceholderExprSyntax.self),
+          .node(EditorPlaceholderPatternSyntax.self),
           .node(EffectsAttributeArgumentListSyntax.self),
           .node(EnumCaseDeclSyntax.self),
           .node(EnumCaseElementListSyntax.self),

Sources/SwiftSyntax/generated/SyntaxEnum.swift

@@ -105,6 +105,7 @@ public enum SyntaxEnum {
   case dynamicReplacementAttributeArguments(DynamicReplacementAttributeArgumentsSyntax)
   case editorPlaceholderDecl(EditorPlaceholderDeclSyntax)
   case editorPlaceholderExpr(EditorPlaceholderExprSyntax)
+  case editorPlaceholderPattern(EditorPlaceholderPatternSyntax)
   case effectsAttributeArgumentList(EffectsAttributeArgumentListSyntax)
   case enumCaseDecl(EnumCaseDeclSyntax)
   case enumCaseElementList(EnumCaseElementListSyntax)
@@ -479,6 +480,8 @@ public extension Syntax {
       return .editorPlaceholderDecl(EditorPlaceholderDeclSyntax(self)!)
     case .editorPlaceholderExpr:
       return .editorPlaceholderExpr(EditorPlaceholderExprSyntax(self)!)
+    case .editorPlaceholderPattern:
+      return .editorPlaceholderPattern(EditorPlaceholderPatternSyntax(self)!)
     case .effectsAttributeArgumentList:
       return .effectsAttributeArgumentList(EffectsAttributeArgumentListSyntax(self)!)
     case .enumCaseDecl:

Sources/SwiftSyntax/generated/SyntaxKind.swift

@@ -105,6 +105,7 @@ public enum SyntaxKind: CaseIterable {
   case dynamicReplacementAttributeArguments
   case editorPlaceholderDecl
   case editorPlaceholderExpr
+  case editorPlaceholderPattern
   case effectsAttributeArgumentList
   case enumCaseDecl
   case enumCaseElementList
@@ -600,6 +601,8 @@ public enum SyntaxKind: CaseIterable {
       return EditorPlaceholderDeclSyntax.self
     case .editorPlaceholderExpr:
       return EditorPlaceholderExprSyntax.self
+    case .editorPlaceholderPattern:
+      return EditorPlaceholderPatternSyntax.self
     case .effectsAttributeArgumentList:
       return EffectsAttributeArgumentListSyntax.self
     case .enumCaseDecl:

Sources/SwiftSyntax/generated/SyntaxRewriter.swift

@@ -710,6 +710,13 @@ open class SyntaxRewriter {
     return ExprSyntax(visitChildren(node))
   }
 
+  /// Visit a ``EditorPlaceholderPatternSyntax``.
+  ///   - Parameter node: the node that is being visited
+  ///   - Returns: the rewritten node
+  open func visit(_ node: EditorPlaceholderPatternSyntax) -> PatternSyntax {
+    return PatternSyntax(visitChildren(node))
+  }
+  
   /// Visit a ``EffectsAttributeArgumentListSyntax``.
   ///   - Parameter node: the node that is being visited
   ///   - Returns: the rewritten node
@@ -2456,6 +2463,10 @@ open class SyntaxRewriter {
       return {
         self.visitImpl($0, EditorPlaceholderExprSyntax.self, self.visit)
       }
+    case .editorPlaceholderPattern:
+      return {
+        self.visitImpl($0, EditorPlaceholderPatternSyntax.self, self.visit)
+      }
     case .effectsAttributeArgumentList:
       return {
         self.visitImpl($0, EffectsAttributeArgumentListSyntax.self, self.visit)
@@ -3390,6 +3401,8 @@ open class SyntaxRewriter {
       return visitImpl(node, EditorPlaceholderDeclSyntax.self, visit)
     case .editorPlaceholderExpr:
       return visitImpl(node, EditorPlaceholderExprSyntax.self, visit)
+    case .editorPlaceholderPattern:
+      return visitImpl(node, EditorPlaceholderPatternSyntax.self, visit)
     case .effectsAttributeArgumentList:
       return visitImpl(node, EffectsAttributeArgumentListSyntax.self, visit)
     case .enumCaseDecl:

Sources/SwiftSyntax/generated/SyntaxTransform.swift

@@ -470,6 +470,11 @@ public protocol SyntaxTransformVisitor {
   ///   - Returns: the sum of whatever the child visitors return.
   func visit(_ node: EditorPlaceholderExprSyntax) -> ResultType
 
+  /// Visiting ``EditorPlaceholderPatternSyntax`` specifically.
+  ///   - Parameter node: the node we are visiting.
+  ///   - Returns: the sum of whatever the child visitors return.
+  func visit(_ node: EditorPlaceholderPatternSyntax) -> ResultType
+  
   /// Visiting ``EffectsAttributeArgumentListSyntax`` specifically.
   ///   - Parameter node: the node we are visiting.
   ///   - Returns: the sum of whatever the child visitors return.
@@ -2036,6 +2041,13 @@ extension SyntaxTransformVisitor {
     visitAny(Syntax(node))
   }
 
+  /// Visiting ``EditorPlaceholderPatternSyntax`` specifically.
+  ///   - Parameter node: the node we are visiting.
+  ///   - Returns: nil by default.
+  public func visit(_ node: EditorPlaceholderPatternSyntax) -> ResultType {
+    visitAny(Syntax(node))
+  }
+  
   /// Visiting ``EffectsAttributeArgumentListSyntax`` specifically.
   ///   - Parameter node: the node we are visiting.
   ///   - Returns: nil by default.
@@ -3522,6 +3534,8 @@ extension SyntaxTransformVisitor {
       return visit(derived)
     case .editorPlaceholderExpr(let derived):
       return visit(derived)
+    case .editorPlaceholderPattern(let derived):
+      return visit(derived)
     case .effectsAttributeArgumentList(let derived):
       return visit(derived)
     case .enumCaseDecl(let derived):

Sources/SwiftSyntax/generated/SyntaxVisitor.swift

@@ -1114,6 +1114,18 @@ open class SyntaxVisitor {
   open func visitPost(_ node: EditorPlaceholderExprSyntax) {
   }
 
+  /// Visiting ``EditorPlaceholderPatternSyntax`` specifically.
+  ///   - Parameter node: the node we are visiting.
+  ///   - Returns: how should we continue visiting.
+  open func visit(_ node: EditorPlaceholderPatternSyntax) -> SyntaxVisitorContinueKind {
+    return .visitChildren
+  }
+  
+  /// The function called after visiting ``EditorPlaceholderPatternSyntax`` and its descendants.
+  ///   - node: the node we just finished visiting.
+  open func visitPost(_ node: EditorPlaceholderPatternSyntax) {
+  }
+  
   /// Visiting ``EffectsAttributeArgumentListSyntax`` specifically.
   ///   - Parameter node: the node we are visiting.
   ///   - Returns: how should we continue visiting.
@@ -3768,6 +3780,10 @@ open class SyntaxVisitor {
       return {
         self.visitImpl($0, EditorPlaceholderExprSyntax.self, self.visit, self.visitPost)
       }
+    case .editorPlaceholderPattern:
+      return {
+        self.visitImpl($0, EditorPlaceholderPatternSyntax.self, self.visit, self.visitPost)
+      }
     case .effectsAttributeArgumentList:
       return {
         self.visitImpl($0, EffectsAttributeArgumentListSyntax.self, self.visit, self.visitPost)
@@ -4705,6 +4721,8 @@ open class SyntaxVisitor {
       visitImpl(node, EditorPlaceholderDeclSyntax.self, visit, visitPost)
     case .editorPlaceholderExpr:
       visitImpl(node, EditorPlaceholderExprSyntax.self, visit, visitPost)
+    case .editorPlaceholderPattern:
+      visitImpl(node, EditorPlaceholderPatternSyntax.self, visit, visitPost)
     case .effectsAttributeArgumentList:
       visitImpl(node, EffectsAttributeArgumentListSyntax.self, visit, visitPost)
     case .enumCaseDecl:

Sources/SwiftSyntax/generated/raw/RawSyntaxNodesEF.swift

@@ -141,6 +141,64 @@ public struct RawEditorPlaceholderExprSyntax: RawExprSyntaxNodeProtocol {
   }
 }
 
+@_spi(RawSyntax)
+public struct RawEditorPlaceholderPatternSyntax: RawPatternSyntaxNodeProtocol {
+  @_spi(RawSyntax)
+  public var layoutView: RawSyntaxLayoutView {
+    return raw.layoutView!
+  }
+  
+  public static func isKindOf(_ raw: RawSyntax) -> Bool {
+    return raw.kind == .editorPlaceholderPattern
+  }
+  
+  public var raw: RawSyntax
+  
+  init(raw: RawSyntax) {
+    precondition(Self.isKindOf(raw))
+    self.raw = raw
+  }
+  
+  private init(unchecked raw: RawSyntax) {
+    self.raw = raw
+  }
+  
+  public init?(_ other: some RawSyntaxNodeProtocol) {
+    guard Self.isKindOf(other.raw) else {
+      return nil
+    }
+    self.init(unchecked: other.raw)
+  }
+  
+  public init(
+      _ unexpectedBeforePlaceholder: RawUnexpectedNodesSyntax? = nil, 
+      placeholder: RawTokenSyntax, 
+      _ unexpectedAfterPlaceholder: RawUnexpectedNodesSyntax? = nil, 
+      arena: __shared SyntaxArena
+    ) {
+    let raw = RawSyntax.makeLayout(
+      kind: .editorPlaceholderPattern, uninitializedCount: 3, arena: arena) { layout in
+      layout.initialize(repeating: nil)
+      layout[0] = unexpectedBeforePlaceholder?.raw
+      layout[1] = placeholder.raw
+      layout[2] = unexpectedAfterPlaceholder?.raw
+    }
+    self.init(unchecked: raw)
+  }
+  
+  public var unexpectedBeforePlaceholder: RawUnexpectedNodesSyntax? {
+    layoutView.children[0].map(RawUnexpectedNodesSyntax.init(raw:))
+  }
+  
+  public var placeholder: RawTokenSyntax {
+    layoutView.children[1].map(RawTokenSyntax.init(raw:))!
+  }
+  
+  public var unexpectedAfterPlaceholder: RawUnexpectedNodesSyntax? {
+    layoutView.children[2].map(RawUnexpectedNodesSyntax.init(raw:))
+  }
+}
+
 @_spi(RawSyntax)
 public struct RawEffectsAttributeArgumentListSyntax: RawSyntaxNodeProtocol {
   @_spi(RawSyntax)

Sources/SwiftSyntax/generated/raw/RawSyntaxNodesOP.swift

@@ -1222,7 +1222,7 @@ public struct RawPatternSyntax: RawPatternSyntaxNodeProtocol {
 
   public static func isKindOf(_ raw: RawSyntax) -> Bool {
     switch raw.kind {
-    case .expressionPattern, .identifierPattern, .isTypePattern, .missingPattern, .tuplePattern, .valueBindingPattern, .wildcardPattern:
+    case .editorPlaceholderPattern, .expressionPattern, .identifierPattern, .isTypePattern, .missingPattern, .tuplePattern, .valueBindingPattern, .wildcardPattern:
       return true
     default:
       return false

Sources/SwiftSyntax/generated/raw/RawSyntaxValidation.swift

@@ -1035,6 +1035,11 @@ func validateLayout(layout: RawSyntaxBuffer, as kind: SyntaxKind) {
     assertNoError(kind, 0, verify(layout[0], as: RawUnexpectedNodesSyntax?.self))
     assertNoError(kind, 1, verify(layout[1], as: RawTokenSyntax.self, tokenChoices: [.tokenKind(.identifier)]))
     assertNoError(kind, 2, verify(layout[2], as: RawUnexpectedNodesSyntax?.self))
+  case .editorPlaceholderPattern:
+    assert(layout.count == 3)
+    assertNoError(kind, 0, verify(layout[0], as: RawUnexpectedNodesSyntax?.self))
+    assertNoError(kind, 1, verify(layout[1], as: RawTokenSyntax.self, tokenChoices: [.tokenKind(.identifier)]))
+    assertNoError(kind, 2, verify(layout[2], as: RawUnexpectedNodesSyntax?.self))
   case .effectsAttributeArgumentList:
     for (index, element) in layout.enumerated() {
       assertNoError(kind, index, verify(element, as: RawTokenSyntax.self))