[clang] Warn about unnecessary virtual specifiers

[zmodem]

Consider:

struct S final {
  virtual void foo();
};

S::foo() doesn't override anything and it cannot be overridden because S is final, so declaring it virtual is wasteful and the compiler could warn about that.

---

Maybe not as useful but in a similar vein, Clang could warn about members which are known never to be overridden because the class is local to the file, for example:

namespace {
struct S {
  virtual void foo() { ... }
};
}

[... no classes derived from S, or at least none that override S::foo() ... ]

[EugeneZelenko]

Isn't this Clang-Tidy modernize-use-override?

[zmodem]

Isn't this Clang-Tidy modernize-use-override?

No, at least based on the docs that sounds like it's addressing a different issue (using override instead of virtual). This one is about functions that don't need to be virtual at all.

[zmodem]

@DKLoehr said he'd take a look.

[seanm]

Looks like a fix was merged. Should this be closed?