Extra IntelliSense errors caused by include paths and precompiled headers

[rpjohnst]

Environment

Windows build number: 10.0.18363.0
Windows Terminal version (if applicable): master branch, commit fc083296b98a2c45126da7a0a61a2ccb37786e48
Visual Studio 2019, 16.6

Steps to reproduce

• Clone the project as described in the README.
• Open OpenConsole.sln in Visual Studio, switch the platform from "Any CPU" to "x64," and build the TerminalAppLib project.
• Open TerminalPage.cpp (under controls/TerminalPage.xaml in the solution explorer).

Expected behavior

IntelliSense should not show any errors/red squiggles, given that the build succeeded.

Actual behavior

IntelliSense finds the wrong pch.h file and goes on to produce a few hundred errors about missing definitions.

Specifically, it finds src\cascadia\TerminalApp\pch.h instead of src\cascadia\TerminalApp\lib\pch.h. You can confirm this by using Go To Definition/F12 on the #include "pch.h" at the top of TerminalPage.cpp. Changing this to #include "lib/pch.h", or making an equivalent change to the project include paths, lets IntelliSense find the right header and all the errors disappear.

The build succeeds because the compiler does not use the usual include path search for this header when PCH is enabled, while IntelliSense fails because its PCH implementation does not work this way.

[DHowett]

This is the first time we've ever had a lead on exactly why IntelliSense is busted in our project. Thank you!

[mpela81]

Thanks @rpjohnst for filing this following my post on Developer Community!