[SWIFT4] Value of type XX has no member 'map'

Description

When using using Objc compatible code, the produced code is not valid in Swift 3/4.

Using openapi-generator Version 3.3.2

with the command:

openapi-generator generate \
	-i ./openAPI-3.yaml \
	--config ./api-generation-config.json \
	-g swift4 \

and the config file api-generation-config.json:

{
...
"objcCompatible":"true",
"podswift_version":"4.0"
}

and the yaml:

definitions:
  ModelA:
    required:
      - intA
    properties:
      intA:
        type: integer
        format: int64
      name:
        type: string

produces this code:

public struct ModelA: Codable {

    public var intA: Int64
    public var intANum: NSNumber? {
        get {
            return intA.map({ return NSNumber(value: $0) })
        }
    }
    public var name: String?

    public init(intA: Int64, name: String?) {
        self.intA = intA
        self.name = name
    }
}

resulting in the error:
- ERROR | xcodebuild: ModelA.swift: error: value of type 'Int64' has no member 'map'

This occurs for type Int64 and Bool.

Start with the swift4 generation path invoked by -g swift4, using the shown objcCompatible configuration and OpenAPI input. Reproduce the generated ModelA code and inspect the handling of Int64 and Bool properties. Done means the generated Swift 3/4 code builds without the reported map errors.