PDFReader 2.5.1 is not recognized as a Swift4 project

[MarcoFilosi]

PDFReader 2.5.1 has been written in Swift4 but CocoaPods 1.3.1 install it as a Swift 3.2 project

Version Info

• PDFReader version: 2.5.1
• CocoaPods version: 1.3.1
• XCode version: 9.1 (9B55)

Expected Behavior

Execute pod install and then compile project on XCode as a Swift 4 project.

Actual Behavior

20 Swift Compiler Errors. Error messages are: xxx is inaccessible due to 'private' protection level

Steps to Reproduce

1. Install XCode 9.1 and CocoaPods 1.3.1
2. Run a project that depends on PDFReader 2.5.1
3. XCode cannot compile project because of PDFReader errors

[MarcoFilosi]

This is not an issue on PDFReader Pod. This is an issue on CocoaPods when we have project importing pods set to a specific swift version but pod is configured with another swift version.
see also:
CocoaPods/CocoaPods#6791
CocoaPods/CocoaPods#7134

CocoaPods 1.4.0 should fix and support multiple swift languages versions

[zaifz]

Go to PDFReader Target - BuildSettings. Select Swift Language Version as Swift 4