@MustInjected replace var:!

README.md

init injection

class DIFormInit {
  let i: Int
  init(i: Int) {
    self.i = i
  }
}

must have by Optional

class DIFormProperty {
  var i: Int!
}

Must Injection

class DIFormMustHave {
  @MustInjected(file: #file, line: #line) 
  var i: Int
}

MustInjected.swift

@propertyWrapper struct MustInjected<Value> {
    private var _value: Value! = nil
    #if DEBUG
    let line: UInt
    let file: StaticString
    #endif
    @available(*, unavailable)
    init(wrappedValue: @autoclosure @escaping () -> Value) {
        self._value = nil
        line = #line
        file = #file
    }
    
    var wrappedValue: Value {
        mutating get {
            #if DEBUG
          precondition(_value != nil, "This property must be inject before access", file: file, line: line)
            #endif
            return _value
        }
        set {
            #if DEBUG
            precondition(_value == nil, "This property is actcully a Let property", file: file, line: line)
            #endif
            _value = newValue
        }
    }
}

extension MustInjected {
    init(file: StaticString, line: UInt) {
        self._value = nil
        #if DEBUG
        self.file = file
        self.line = line
        #endif
    }
}