Two commits are split out from #16710 to make reviewing easier.
From C++ FAQ:
C.128: Virtual functions should specify exactly one of virtual, override, or final Reason Readability. Detection of mistakes. Writing explicit
virtual,override, orfinalis self-documenting and enables the compiler to catch mismatch of types and/or names between base and derived classes. However, writing more than one of these three is both redundant and a potential source of errors.
The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.
Reviewers, this pull request conflicts with the following ones:
If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.
override prevents bugs + patch looks correct + Travis happy
override or final to a function must always be correct, unless it doesn’t compile!?
override is used when nobody is further overriding a given method then it is better to use final instead of override. This will compile. Even in this case it is better to have override instead of nothing.
It’s my understanding that changing final/override can never affect semantics, only potentially change whether something compiles or not.
In addition, override imples virtual, and final implies override, so it should never be needed to specify more than one of these 3.