[cfe-dev] Marking declarations as invalid

[Nathan Wilson via cfe-dev]

On Nov 5, 2015 5:18 PM, "Richard Smith" <richard at metafoo.co.uk> wrote:
>
> On Thu, Oct 29, 2015 at 8:04 PM, Nathan Wilson via cfe-dev <
cfe-dev at lists.llvm.org> wrote:
>>
>> Hi,
>>
>> Would someone mind explaining when (or when not) to mark a declaration,
i.e. FunctionDecl or VarDecl, an invalid declaration?
>>
>> Then, if the declaration is marked invalid, at what do we look at/use
that information?
>
> Here are some guidelines:
>
>   * You must not mark a declaration as invalid unless you have emitted an
error.
>   * If you emitted an error with a fix-it hint, you should not mark the
declaration as invalid (and you should recover as if the fix-it hint were
applied). We would like this to be a hard rule, but there are existing
cases where we don't follow this.
>   * You should mark a declaration as invalid if you think it's
sufficiently far from the user's intent that follow-on diagnostics should
be suppressed.
>   * You must mark a declaration as invalid if it does not correspond to
anything like a valid declaration (if it would be unreasonable to expect
downstream code to do the right thing with it).

Thanks for this Richard. That helps a lot.

So, I could (should?) have used a fix-it hint in the example above and not
mark the declaration invalid, correct? (Aside from your third bullet.)

Would you be able to give an example of the fourth bullet and/or point to
where the downstream code would do the right thing?
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