When replacing a node’s child, make sure the new child doesn’t get pre-maturely deallocated

Previously, depending on the optimization level, when changing a nodes’s property, it could happen that `value` got de-allocated (because only `value.raw` was being accessed), deallocating the arena that `value.raw` lives in, resulting in freed memory access.

Author: ahoppen

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

@@ -173,7 +173,7 @@ func syntaxNode(emitKind: SyntaxNodeKind) -> SourceFileSyntax {
             AccessorDeclSyntax(
               """
               set(value) {
-                self = \(node.kind.syntaxType)(data.replacingChild(at: \(raw: index), with: value\(raw: child.isOptional ? "?" : "").raw, arena: SyntaxArena()))
+                self = \(node.kind.syntaxType)(data.replacingChild(at: \(raw: index), with: value\(raw: child.isOptional ? "?" : "").data, arena: SyntaxArena()))
               }
               """
             )

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

@@ -342,8 +342,9 @@ let syntaxRewriterFile = SourceFileSyntax(leadingTrivia: copyrightHeader) {
       /// 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))
+        return withExtendedLifetime(rewritten) {
+          return Syntax(node.data.replacingSelf(rewritten.raw, arena: rewritten.raw.arena))
+        }
       }
       """
     )

Sources/SwiftSyntax/SyntaxData.swift

@@ -336,6 +336,15 @@ struct SyntaxData {
     return replacingSelf(newRaw, arena: arena)
   }
 
+  /// Identical to `replacingChild(at: Int, with: RawSyntax?, arena: SyntaxArena)`
+  /// that ensures that the arena of`newChild` doesn’t get de-allocated before
+  /// `newChild` has been addded to the result.
+  func replacingChild(at index: Int, with newChild: SyntaxData?, arena: SyntaxArena) -> SyntaxData {
+    return withExtendedLifetime(newChild) {
+      return replacingChild(at: index, with: newChild?.raw, arena: arena)
+    }
+  }
+
   func withLeadingTrivia(_ leadingTrivia: Trivia, arena: SyntaxArena) -> SyntaxData {
     if let raw = raw.withLeadingTrivia(leadingTrivia, arena: arena) {
       return replacingSelf(raw, arena: arena)

Sources/SwiftSyntax/generated/syntaxNodes/SyntaxDeclNodes.swift

@@ -63,7 +63,7 @@ public struct ExpressionPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 0, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = ExpressionPatternSyntax(data.replacingChild(at: 0, with: value?.raw, arena: SyntaxArena()))
+      self = ExpressionPatternSyntax(data.replacingChild(at: 0, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -72,7 +72,7 @@ public struct ExpressionPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return ExprSyntax(data.child(at: 1, parent: Syntax(self))!)
     }
     set(value) {
-      self = ExpressionPatternSyntax(data.replacingChild(at: 1, with: value.raw, arena: SyntaxArena()))
+      self = ExpressionPatternSyntax(data.replacingChild(at: 1, with: value.data, arena: SyntaxArena()))
     }
   }
 
@@ -81,7 +81,7 @@ public struct ExpressionPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 2, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = ExpressionPatternSyntax(data.replacingChild(at: 2, with: value?.raw, arena: SyntaxArena()))
+      self = ExpressionPatternSyntax(data.replacingChild(at: 2, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -141,7 +141,7 @@ public struct IdentifierPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 0, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = IdentifierPatternSyntax(data.replacingChild(at: 0, with: value?.raw, arena: SyntaxArena()))
+      self = IdentifierPatternSyntax(data.replacingChild(at: 0, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -150,7 +150,7 @@ public struct IdentifierPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return TokenSyntax(data.child(at: 1, parent: Syntax(self))!)
     }
     set(value) {
-      self = IdentifierPatternSyntax(data.replacingChild(at: 1, with: value.raw, arena: SyntaxArena()))
+      self = IdentifierPatternSyntax(data.replacingChild(at: 1, with: value.data, arena: SyntaxArena()))
     }
   }
 
@@ -159,7 +159,7 @@ public struct IdentifierPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 2, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = IdentifierPatternSyntax(data.replacingChild(at: 2, with: value?.raw, arena: SyntaxArena()))
+      self = IdentifierPatternSyntax(data.replacingChild(at: 2, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -233,7 +233,7 @@ public struct IsTypePatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 0, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = IsTypePatternSyntax(data.replacingChild(at: 0, with: value?.raw, arena: SyntaxArena()))
+      self = IsTypePatternSyntax(data.replacingChild(at: 0, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -242,7 +242,7 @@ public struct IsTypePatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return TokenSyntax(data.child(at: 1, parent: Syntax(self))!)
     }
     set(value) {
-      self = IsTypePatternSyntax(data.replacingChild(at: 1, with: value.raw, arena: SyntaxArena()))
+      self = IsTypePatternSyntax(data.replacingChild(at: 1, with: value.data, arena: SyntaxArena()))
     }
   }
 
@@ -251,7 +251,7 @@ public struct IsTypePatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 2, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = IsTypePatternSyntax(data.replacingChild(at: 2, with: value?.raw, arena: SyntaxArena()))
+      self = IsTypePatternSyntax(data.replacingChild(at: 2, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -260,7 +260,7 @@ public struct IsTypePatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return TypeSyntax(data.child(at: 3, parent: Syntax(self))!)
     }
     set(value) {
-      self = IsTypePatternSyntax(data.replacingChild(at: 3, with: value.raw, arena: SyntaxArena()))
+      self = IsTypePatternSyntax(data.replacingChild(at: 3, with: value.data, arena: SyntaxArena()))
     }
   }
 
@@ -269,7 +269,7 @@ public struct IsTypePatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 4, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = IsTypePatternSyntax(data.replacingChild(at: 4, with: value?.raw, arena: SyntaxArena()))
+      self = IsTypePatternSyntax(data.replacingChild(at: 4, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -335,7 +335,7 @@ public struct MissingPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 0, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = MissingPatternSyntax(data.replacingChild(at: 0, with: value?.raw, arena: SyntaxArena()))
+      self = MissingPatternSyntax(data.replacingChild(at: 0, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -345,7 +345,7 @@ public struct MissingPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return TokenSyntax(data.child(at: 1, parent: Syntax(self))!)
     }
     set(value) {
-      self = MissingPatternSyntax(data.replacingChild(at: 1, with: value.raw, arena: SyntaxArena()))
+      self = MissingPatternSyntax(data.replacingChild(at: 1, with: value.data, arena: SyntaxArena()))
     }
   }
 
@@ -354,7 +354,7 @@ public struct MissingPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 2, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = MissingPatternSyntax(data.replacingChild(at: 2, with: value?.raw, arena: SyntaxArena()))
+      self = MissingPatternSyntax(data.replacingChild(at: 2, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -434,7 +434,7 @@ public struct TuplePatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 0, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = TuplePatternSyntax(data.replacingChild(at: 0, with: value?.raw, arena: SyntaxArena()))
+      self = TuplePatternSyntax(data.replacingChild(at: 0, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -443,7 +443,7 @@ public struct TuplePatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return TokenSyntax(data.child(at: 1, parent: Syntax(self))!)
     }
     set(value) {
-      self = TuplePatternSyntax(data.replacingChild(at: 1, with: value.raw, arena: SyntaxArena()))
+      self = TuplePatternSyntax(data.replacingChild(at: 1, with: value.data, arena: SyntaxArena()))
     }
   }
 
@@ -452,7 +452,7 @@ public struct TuplePatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 2, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = TuplePatternSyntax(data.replacingChild(at: 2, with: value?.raw, arena: SyntaxArena()))
+      self = TuplePatternSyntax(data.replacingChild(at: 2, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -461,7 +461,7 @@ public struct TuplePatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return TuplePatternElementListSyntax(data.child(at: 3, parent: Syntax(self))!)
     }
     set(value) {
-      self = TuplePatternSyntax(data.replacingChild(at: 3, with: value.raw, arena: SyntaxArena()))
+      self = TuplePatternSyntax(data.replacingChild(at: 3, with: value.data, arena: SyntaxArena()))
     }
   }
 
@@ -489,7 +489,7 @@ public struct TuplePatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 4, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = TuplePatternSyntax(data.replacingChild(at: 4, with: value?.raw, arena: SyntaxArena()))
+      self = TuplePatternSyntax(data.replacingChild(at: 4, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -498,7 +498,7 @@ public struct TuplePatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return TokenSyntax(data.child(at: 5, parent: Syntax(self))!)
     }
     set(value) {
-      self = TuplePatternSyntax(data.replacingChild(at: 5, with: value.raw, arena: SyntaxArena()))
+      self = TuplePatternSyntax(data.replacingChild(at: 5, with: value.data, arena: SyntaxArena()))
     }
   }
 
@@ -507,7 +507,7 @@ public struct TuplePatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 6, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = TuplePatternSyntax(data.replacingChild(at: 6, with: value?.raw, arena: SyntaxArena()))
+      self = TuplePatternSyntax(data.replacingChild(at: 6, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -589,7 +589,7 @@ public struct ValueBindingPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 0, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = ValueBindingPatternSyntax(data.replacingChild(at: 0, with: value?.raw, arena: SyntaxArena()))
+      self = ValueBindingPatternSyntax(data.replacingChild(at: 0, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -598,7 +598,7 @@ public struct ValueBindingPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return TokenSyntax(data.child(at: 1, parent: Syntax(self))!)
     }
     set(value) {
-      self = ValueBindingPatternSyntax(data.replacingChild(at: 1, with: value.raw, arena: SyntaxArena()))
+      self = ValueBindingPatternSyntax(data.replacingChild(at: 1, with: value.data, arena: SyntaxArena()))
     }
   }
 
@@ -607,7 +607,7 @@ public struct ValueBindingPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 2, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = ValueBindingPatternSyntax(data.replacingChild(at: 2, with: value?.raw, arena: SyntaxArena()))
+      self = ValueBindingPatternSyntax(data.replacingChild(at: 2, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -616,7 +616,7 @@ public struct ValueBindingPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return PatternSyntax(data.child(at: 3, parent: Syntax(self))!)
     }
     set(value) {
-      self = ValueBindingPatternSyntax(data.replacingChild(at: 3, with: value.raw, arena: SyntaxArena()))
+      self = ValueBindingPatternSyntax(data.replacingChild(at: 3, with: value.data, arena: SyntaxArena()))
     }
   }
 
@@ -625,7 +625,7 @@ public struct ValueBindingPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 4, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = ValueBindingPatternSyntax(data.replacingChild(at: 4, with: value?.raw, arena: SyntaxArena()))
+      self = ValueBindingPatternSyntax(data.replacingChild(at: 4, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -705,7 +705,7 @@ public struct WildcardPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 0, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = WildcardPatternSyntax(data.replacingChild(at: 0, with: value?.raw, arena: SyntaxArena()))
+      self = WildcardPatternSyntax(data.replacingChild(at: 0, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -714,7 +714,7 @@ public struct WildcardPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return TokenSyntax(data.child(at: 1, parent: Syntax(self))!)
     }
     set(value) {
-      self = WildcardPatternSyntax(data.replacingChild(at: 1, with: value.raw, arena: SyntaxArena()))
+      self = WildcardPatternSyntax(data.replacingChild(at: 1, with: value.data, arena: SyntaxArena()))
     }
   }
 
@@ -723,7 +723,7 @@ public struct WildcardPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 2, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = WildcardPatternSyntax(data.replacingChild(at: 2, with: value?.raw, arena: SyntaxArena()))
+      self = WildcardPatternSyntax(data.replacingChild(at: 2, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -732,7 +732,7 @@ public struct WildcardPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 3, parent: Syntax(self)).map(TypeAnnotationSyntax.init)
     }
     set(value) {
-      self = WildcardPatternSyntax(data.replacingChild(at: 3, with: value?.raw, arena: SyntaxArena()))
+      self = WildcardPatternSyntax(data.replacingChild(at: 3, with: value?.data, arena: SyntaxArena()))
     }
   }
 
@@ -741,7 +741,7 @@ public struct WildcardPatternSyntax: PatternSyntaxProtocol, SyntaxHashable {
       return data.child(at: 4, parent: Syntax(self)).map(UnexpectedNodesSyntax.init)
     }
     set(value) {
-      self = WildcardPatternSyntax(data.replacingChild(at: 4, with: value?.raw, arena: SyntaxArena()))
+      self = WildcardPatternSyntax(data.replacingChild(at: 4, with: value?.data, arena: SyntaxArena()))
     }
   }