Help needed : contributing to Sytem.Private.CoreLib

[CarlVerret]

Hi there,
Following an issue that had been accepted by System.Runtime area manager, I'm trying to contribute to S.P.C. with a PR.
For some reason, I can't figure out how to add a new stuff to the double class.

Lets say I'd like to add a simple function like this one (this is a simple example for sake of simplicity ) :

public static bool ReturnFalse()=> false;

Been building S.P.C. with success and even after using :
build.cmd clr.corelib+clr.nativecorelib+libs.pretest
I still can't see this new function inside System.Runtime.Tests. Having a hard time trying to understand the build worklfow....

Can someone please help me figure out what I am missing ? I am using VS2022 on Windows 10.

[huoyaoyuan]

A new public member must be defined in both implementation and reference api.
The reference api of System.Private.CoreLib should be in System.Runtime/ref.