I updated to Microsoft.Windows.CppWinRT.2.0.201102.2 (was on 2.0.200729.8) and now get build errors in a console app project that contains a .idl file. midl.exe reports an internal error.
The response files contents are the problem, containing .winmd references from multiple copies of the SDK.
1> C:\Program Files (x86)\Windows Kits\10\bin\10.0.19041.0\x64\midl.exe /metadata_dir "C:\Program Files (x86)\Windows Kits\10\References\10.0.19041.0\windows.foundation.foundationcontract\4.0.0.0" /winrt /W1 /nologo /char signed /env x64 /winmd "x64\Debug\Unmerged\MyClass.winmd" /h "nul" /dlldata "nul" /iid "nul" /proxy "nul" /notlb /client none /server none /target "NT60" /nomidl @"x64\Debug\CppWinRtClient.vcxproj.midlrt.rsp" MyClass.idl
...
1> Processing WinMD c:\program files (x86)\windows kits\10\references\10.0.17763.0\windows.ai.machinelearning.machinelearningcontract\1.0.0.0\windows.ai.machinelearning.machinelearningcontract.winmd
...
1> Processing WinMD c:\program files (x86)\windows kits\10\references\10.0.18362.0\windows.ai.machinelearning.machinelearningcontract\2.0.0.0\windows.ai.machinelearning.machinelearningcontract.winmd
...
1> Processing WinMD c:\program files (x86)\windows kits\10\references\10.0.19041.0\windows.ai.machinelearning.machinelearningcontract\3.0.0.0\windows.ai.machinelearning.machinelearningcontract.winmd
I see #781 might be related. either fixing, or causing this problem.