Swift编译报错：Command SwiftCompile返回非零退出码（无语法错误）

核心问题1：枚举成员拼写错误 #

代码里的Constraints枚举存在拼写错误：toWigth应为toWidth，这个错误会导致编译器无法正确解析枚举case，进而触发编译失败。

核心问题2：Switch语句中枚举case缺少前缀. #

在Swift 5.8（对应Xcode 14.3）中，跨上下文引用枚举case必须添加.前缀，你的switch语句里所有case都省略了这个前缀，这是编译失败的另一个关键原因。

修正后的完整代码 #

import Foundation
import UIKit

enum Constraints<T> {
    case setTop(to: T, constant: CGFloat = 0)
    case setBottom(to: T, constant: CGFloat = 0)
    case setLeading(to: T, constant: CGFloat = 0)
    case setTrailing(to: T, constant: CGFloat = 0)
    case toBottom(of: T, constant: CGFloat = 0)
    case toTop(of: T, constant: CGFloat = 0)
    case toLeading(of: T, constant: CGFloat = 0)
    case toTrailing(of: T, constant: CGFloat = 0)
    case toHeight(of: T, multiplier: CGFloat = 1)
    case toWidth(of: T, multiplier: CGFloat = 1) // 修复拼写错误
}

extension UIView {
    func applyConstraints(_ constraints: Constraints<UIView>...) {
        self.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate(constraints.map { constraint in
            switch constraint {
            case .setTop(to: let to, constant: let constant): // 添加.前缀
                return self.topAnchor.constraint(equalTo: to.topAnchor, constant: constant)
             case .setBottom(to: let to, constant: let constant): // 添加.前缀
                return self.bottomAnchor.constraint(equalTo: to.bottomAnchor, constant: constant)
            case .setLeading(to: let to, constant: let constant): // 添加.前缀
                return self.leadingAnchor.constraint(equalTo: to.leadingAnchor, constant: constant)
            case .setTrailing(to: let to, constant: let constant): // 添加.前缀
                return self.trailingAnchor.constraint(equalTo: to.trailingAnchor, constant: constant)
            case .toBottom(of: let of, constant: let constant): // 添加.前缀
                return self.topAnchor.constraint(equalTo: of.bottomAnchor, constant: constant)
            case .toTop(of: let of, constant: let constant): // 添加.前缀
                return self.bottomAnchor.constraint(equalTo: of.topAnchor, constant: constant)
            case .toLeading(of: let of, constant: let constant): // 添加.前缀
                return self.trailingAnchor.constraint(equalTo: of.leadingAnchor, constant: constant)
            case .toTrailing(of: let of, constant: let constant): // 添加.前缀
                return self.leadingAnchor.constraint(equalTo: of.trailingAnchor, constant: constant)
            case .toHeight(of: let of, multiplier: let multiplier): // 添加.前缀
                return self.heightAnchor.constraint(equalTo: of.heightAnchor, multiplier: multiplier)
            case .toWidth(of: let of, multiplier: let multiplier): // 添加.前缀+修复拼写
                return self.widthAnchor.constraint(equalTo: of.widthAnchor, multiplier: multiplier)
            }
        })
    }
}

额外说明 #

你的MainVC使用示例代码无需修改，修正上述问题后即可正常编译运行。另外，Xcode 14.3的Swift编译器对语法规范的检查比旧版本更严格，这也是之前能运行但现在报错的原因之一。

内容的提问来源于stack exchange，提问作者Alexey_BH