UnrealBuildTool problem

I am looking for the way to customize switches that UnrealBuildTool passes to the VC++ compiler during the build process. Specifically I need to compile with /showIncludes and (or) /P switches to investigate an “C2027: use of undefined type…” compilation error. The cause and reason of this error is unclear for me because the header file that defines the required type is included in the compilation unit. I have found VCToolChain.cs file and uncomented Arguments.Add("/showIncludes"); string in AppendCLArguments_Global function. But I can not find any *.i files. Please help me

Can’t really help you with the question directly, but “use of undefined type” usually means you didn’t include the required header, or that you didn’t add the required module to the .Build.cs file.