Noncopyable type the compiler can't verify

[TeamPuzel]

Description

The compiler told me this is a bug and to report it, so here it is

Reproduction

@preconcurrency import GLAD

@_marker
public protocol Uniform {}

public struct Shader: ~Copyable {
    private let id: GLuint
    private var uniformLocations: [String: GLint] = [:]
    private var vertex: String
    private var fragment: String
    
    private static func compile(kind: SourceKind, source: String) -> GLuint { ... }
    public init(vertex: String, fragment: String) throws(CompileError) { ... }
    deinit { glad_glDeleteProgram(self.id) }
    func bind() { glad_glUseProgram(self.id) }
    
    public subscript<T: Uniform>(uniform: String, of type: T.Type) -> T {
        get {
            fatalError()
        }
        set { // The error happens here --------------------------------------------------
            self.uniformLocations[
                uniform,
                default: {
                    uniform.utf8CString.withUnsafeBufferPointer { buffer in
                        glad_glGetUniformLocation(self.id, buffer.baseAddress)
                    }
                }()
            ]
        }
    }
    
    public enum SourceKind: Sendable { case vertex, fragment }
    
    public enum CompileError: Swift.Error {
        case couldNotValidateShader(message: String, vertex: String, fragment: String)
        case couldNotCompileShader(message: String, kind: SourceKind, source: String)
    }
}

Expected behavior

N/A

Environment

Apple Swift version 6.2-dev (LLVM 4930d5a55e7728b, Swift ec5bee8)
Target: arm64-apple-macosx15.0

Additional information

No response