[PATCH] Warn on explicit copy constructors.

[Arthur O'Dwyer]

On Tue, Apr 29, 2014 at 6:58 AM, Alexander Kornienko <alexfh at google.com> wrote:
>
> http://reviews.llvm.org/D3541

> +  if (Ctor->isOutOfLine() || Ctor->isImplicit() || Ctor->isDeleted())
>      return;
> +  if (Ctor->isExplicit() || Ctor->isCopyOrMoveConstructor()) {
> +    if (Ctor->isExplicit() && Ctor->isCopyOrMoveConstructor()) {
> +      SourceRange ExplicitTokenRange = FindToken(
> +          *Result.SourceManager, Result.Context->getLangOpts(),
> +          Ctor->getOuterLocStart(), Ctor->getLocEnd(), [](const Token &Tok) {
> +            return Tok.is(tok::raw_identifier) &&
> +                   StringRef(Tok.getRawIdentifierData(), Tok.getLength()) ==
> +                       "explicit";
> +          });
> +      if (ExplicitTokenRange.isValid()) {
> +        DiagnosticBuilder Diag =
> +            diag(ExplicitTokenRange.getBegin(),
> +                 "Copy constructor declared explicit.");

You mean "copy or move constructor"; and you could use a test for the
move-constructor case.

There are corner cases such as

    C(const C&&);
    C(const C&, int i = 0);
    template<typename T> C(const T&);

that would be interesting to test.

–Arthur