[Syntax] Workaround for 'cannot bypass resilience' warnings

`RawSyntaxArena` and `SyntaxDataaArena` have properties with types from
`_SwiftSyntaxCShims` which is `@_implementationOnly` when compiling with
'-enable-library-evolution`.

But for `-allow-non-resilient-access` for the package cross module
optimizations, they causes warnings:

```
warning: cannot bypass resilience due to member deserialization failure while attempting to access member 'mutex' of 'SyntaxDataArena' in module 'SwiftSyntax' from module 'SwiftSyntax'
warning: cannot bypass resilience due to member deserialization failure while attempting to access member 'hasParent' of 'RawSyntaxArena' in module 'SwiftSyntax' from module 'SwiftSyntax'
```

and non-resilient-access are disabled for these types.

To workaround that, use `UnsafeRawPointer` for those stored properties
and use casting methods to access the actual types.
Note the using computed properties were not enough to silience the
warnings.

Author: rintaro

Sources/SwiftSyntax/Raw/RawSyntaxArena.swift

@@ -63,7 +63,11 @@ public class RawSyntaxArena {
   ///
   /// - Important: This is only intended to be used for assertions to catch
   ///   retain cycles in syntax arenas.
-  fileprivate let hasParent: UnsafeMutablePointer<AtomicBool>
+  /// - Note: `UnsafeMutableRawPointer` + casting accessor is a workaround to silence the warning 'cannot bypass resilience'.
+  private let _hasParent: UnsafeMutableRawPointer
+  fileprivate func hasParent() -> UnsafeMutablePointer<AtomicBool> {
+    _hasParent.assumingMemoryBound(to: AtomicBool.self)
+  }
   #endif
 
   /// Construct a new ``RawSyntaxArena`` in which syntax nodes can be allocated.
@@ -75,7 +79,7 @@ public class RawSyntaxArena {
     self.allocator = BumpPtrAllocator(initialSlabSize: slabSize)
     self.childRefs = []
     #if DEBUG || SWIFTSYNTAX_ENABLE_ASSERTIONS
-    self.hasParent = swiftsyntax_atomic_bool_create(false)
+    self._hasParent = UnsafeMutableRawPointer(swiftsyntax_atomic_bool_create(false))
     #endif
   }
 
@@ -84,7 +88,7 @@ public class RawSyntaxArena {
       child.release()
     }
     #if DEBUG || SWIFTSYNTAX_ENABLE_ASSERTIONS
-    swiftsyntax_atomic_bool_destroy(self.hasParent)
+    swiftsyntax_atomic_bool_destroy(self.hasParent())
     #endif
   }
 
@@ -153,7 +157,7 @@ public class RawSyntaxArena {
 
     #if DEBUG || SWIFTSYNTAX_ENABLE_ASSERTIONS
     precondition(
-      !swiftsyntax_atomic_bool_get(self.hasParent),
+      !swiftsyntax_atomic_bool_get(self.hasParent()),
       "an arena can't have a new child once it's owned by other arenas"
     )
     #endif
@@ -299,12 +303,12 @@ struct RawSyntaxArenaRef: Hashable, @unchecked Sendable {
   #if DEBUG || SWIFTSYNTAX_ENABLE_ASSERTIONS
   /// Accessor for the underlying's `RawSyntaxArena.hasParent`
   var hasParent: Bool {
-    swiftsyntax_atomic_bool_get(value.hasParent)
+    swiftsyntax_atomic_bool_get(value.hasParent())
   }
 
   /// Sets the `RawSyntaxArena.hasParent` on the referenced arena.
   func setHasParent(_ newValue: Bool) {
-    swiftsyntax_atomic_bool_set(value.hasParent, newValue)
+    swiftsyntax_atomic_bool_set(value.hasParent(), newValue)
   }
   #endif
 

Sources/SwiftSyntax/Syntax.swift

@@ -382,7 +382,10 @@ struct SyntaxData: Sendable {
 /// `SyntaxDataArena` manages the entire data of a `Syntax` tree.
 final class SyntaxDataArena: @unchecked Sendable {
   /// Mutex for locking the data when populating layout buffers.
-  private let mutex: PlatformMutex
+  ///
+  /// - Note: `UnsafeMutableRawPointer` + casting accessor is a workaround to silence the warning 'cannot bypass resilience'.
+  private let _mutex: UnsafeMutableRawPointer!
+  private func mutex() -> PlatformMutex { PlatformMutex(opaque: self._mutex) }
 
   /// Allocator.
   private let allocator: BumpPtrAllocator
@@ -396,7 +399,7 @@ final class SyntaxDataArena: @unchecked Sendable {
   init(raw: RawSyntax, rawNodeArena: RetainedRawSyntaxArena) {
     precondition(rawNodeArena == raw.arenaReference)
 
-    self.mutex = PlatformMutex.create()
+    self._mutex = PlatformMutex.create().opaque
     self.allocator = BumpPtrAllocator(initialSlabSize: Self.slabSize(for: raw))
     self.rawArena = rawNodeArena
     self.root = Self.createDataImpl(allocator: allocator, raw: raw, parent: nil, absoluteInfo: .forRoot(raw))
@@ -405,7 +408,7 @@ final class SyntaxDataArena: @unchecked Sendable {
   deinit {
     // Debug print for re-evaluating `slabSize(for:)`
     // print("nodeCount: \(root.pointee.raw.totalNodes), slabSize: \(Self.slabSize(for: root.pointee.raw)), allocated: \(allocator.totalByteSizeAllocated), overflowed: \(Self.slabSize(for: root.pointee.raw) < allocator.totalByteSizeAllocated)")
-    self.mutex.destroy()
+    self.mutex().destroy()
   }
 
   /// Return the childen data of the given node.
@@ -431,8 +434,8 @@ final class SyntaxDataArena: @unchecked Sendable {
       return SyntaxDataReferenceBuffer(UnsafeBufferPointer(start: baseAddress, count: childCount))
     }
 
-    mutex.lock()
-    defer { mutex.unlock() }
+    mutex().lock()
+    defer { mutex().unlock() }
 
     // Recheck, maybe some other thread has populated the buffer during acquiring the lock.
     if let baseAddress = swiftsyntax_atomic_pointer_get(baseAddressRef)?.assumingMemoryBound(