So… I’m following the Player Input and Pawns tutoral found at Player Input and Pawns | Unreal Engine Documentation …
#1 error: you need to add #include <Runtime/Engine/Private/Camera/CameraComponent.cpp> to get it to compile at all. (easily fixed)
#2 error: the compiler flags the MyPawn.cpp file for not including MyPawn.h first if the files included on the page are taken litterally (easily fixed)
#3 error: Many errors of the following form:
|Error|C4273|‘UCameraComponent::UCameraComponent’: inconsistent dll linkage|HowTo_PlayerInput|D:\Epic\UE_4.27\Engine\Source\Runtime\Engine\Private\Camera\CameraComponent.cpp|31||
… which, while I’m an old C++ hand, I don’t play too much in the M$ world — or in the Unreal world (yet) — so I have no idea how to resolve this last error.