xcode-26-2

name: xcode-26.2 description: Fix Xcode 26.2 compiler errors and warnings in Swift files related to Swift concurrency, type system, and memory safety. Use when encountering Swift compiler errors in Xcode 26.2, especially around actor isolation, Sendable conformance, existential types, or strict language features. Applies to all .swift files in this project.

Xcode 26.2 Compiler Error Resolution

Guidance for resolving Xcode 26.2 compiler errors and warnings in Swift code.

Swift Concurrency

Actor Isolation Errors

Calling actor-isolated methods from nonisolated context:

@MainActor
class MyModel {
  func update() { ... }
}

// Error: call to main actor-isolated instance method 'update()' in a synchronous nonisolated context
func runUpdate(model: MyModel) {
  model.update() // ❌
}

Fix: Isolate the caller or wrap in a Task:

@MainActor
func runUpdate(model: MyModel) {
  model.update() // ✅
}

// OR
func runUpdate(model: MyModel) {
  Task { @MainActor in
    model.update() // ✅
  }
}

Protocol Conformances Crossing Actor Boundaries

Error: conformance of 'MyData' to protocol 'P' crosses into main actor-isolated code

Options:

1. Isolate the conformance: struct MyData: @MainActor P
2. Mark methods nonisolated: nonisolated func f()
3. Use @preconcurrency: struct MyData: @preconcurrency P (runtime checks)

Sendable Closures

Error: capture of non-Sendable type 'T' in a '@Sendable' closure

Fix: Capture by value or make type Sendable:

callConcurrently { [result] in  // ✅ Capture by value
  print(result)
}

// OR make type Sendable
class MyModel: Sendable { ... }

Error: sending 'x' risks causing data races

Fix: Use nonisolated(nonsending) for async methods on non-Sendable types:

nonisolated(nonsending)
func printNameConcurrently() async {
  print(name)
}

Sendable Metatypes

Error: capture of non-Sendable type 'T.Type'

Fix: Require SendableMetatype conformance:

func doSomethingStatic<T: P & SendableMetatype>(_: T.Type) {
  Task { @concurrent in
    T.doSomething() // ✅
  }
}

Type System

Existential any Syntax

Error: Protocol used as type without any keyword

Fix: Use any for existential types:

func sillyFunction(collection: any Collection) { // ✅
  // ...
}

String Interpolation Conformance

When conforming to StringInterpolationProtocol, appendInterpolation methods must:

• Be instance methods (not static or class)
• Return Void or be marked @discardableResult
• Be at least as accessible as the containing type

Memory Safety

Strict Memory Safety Warnings

Error: Use of @unsafe functions or types

Fix: Acknowledge unsafe behavior:

// Option 1: unsafe expression
return unsafe Int(bitPattern: malloc(size))

// Option 2: @unsafe attribute
struct MyType: @unsafe CustomStringConvertible { ... }

// Option 3: @safe attribute (encapsulates unsafe)
@safe struct MyTemporaryBuffer<T> {
  private var storage: UnsafeBufferPointer<T>
}

Additional Resources

For detailed documentation on specific error types, see:

• actor-isolated-call.md - Actor isolation issues
• conformance-isolation.md - Protocol conformance isolation
• sendable-closure-captures.md - Sendable closure requirements
• existential-any.md - Existential type syntax
• strict-memory-safety.md - Memory safety warnings
• string-interpolation-conformance.md - String interpolation requirements

Quick Reference