[cfe-dev] Type::isIncompleteType()...

[Chris Lattner]

On Feb 10, 2008, at 9:12 PM, Neil Booth wrote:
> $ ./cfe /tmp/bug.c
> "/tmp/bug.c", line 3: error: members may not have function type
>  int foo();
>      ^
>
> 1 error found compiling "/tmp/bug.c".
>
> I don't think it necessarily makes sense to expect extra diagnostics
> in any particular situation; once something is erroneous there are
> many reasonable recovery strategies.  I think my cfe just ignores
> the foo declaration as if it didn't exist, for example.  Another
> quite reasonable strategy would be to have a member foo in the
> structure but flag it erroneous; this would mean uses of foo wouldn't
> get diagnostics about no such member.

In this specific case (a single malformed field in a struct) I agree  
with Neil: it's best to just recover by dropping that one field decl,  
or change it into a decl with a valid type (in the case of function,  
make it a pointer to function) which is probably even better.  In  
certain parts of type analysis we try really hard to turn an erroneous  
type into a valid one.

As everyone knows, there is a tradeoff here: the more you try to  
"infer" what the user meant, the more likely it is that your guess can  
trigger a cascade of errors.  In this specific case, I think that  
turning a function into a pointer to function is unlikely to do that  
though.

That said, Steve's idea might still be a good one.  In what other  
cases can a struct decl be marked erroneous?

-Chris