Recursive structure def. could use better error diagnostics messages

[llvmbot]

Bugzilla Link	3981
Resolution	WONTFIX
Resolved on	Mar 12, 2010 00:56
Version	unspecified
OS	All
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor,@efriedma-quic

Extended Description

Consider the following C source code:

struct foo;
struct foo { struct foo f; };

The follow error output is produced:

s.c:2:25: error: field has incomplete type 'struct foo'
struct foo { struct foo f; };
^
s.c:2:8: note: definition of 'struct foo' is not complete until the closing '}'
struct foo { struct foo f; };
^
2 diagnostics generated.

These diagnostic messages could be improved. Particularly, the second message is spurious.

On an unrelated note, perhaps "Diagnostics" should be a category in Bugzilla to report bugs against...

[efriedma-quic]

The messages were done this way intentionally... why do you think the second message is spurious?

[llvmbot]

I guess it makes sense - but its confusing because my first thought was that the second message referred not to the inner type but to the outer type (obviously its the same type .. but the way I read it first is that the note is a second error as a result of the previous error rather than an explanation of the previous error).

Perhaps there could be a way to make it more obvious that a note: is explaining the previous error?
Like in the error itself, it could say "(see note: below)" at the end.

[DougGregor]

The error message + note look really, really good to me: it's explaining exactly what the problem is. I'm going to close this; if someone comes up with a better wording for the diagnostics, please re-open with that suggestion.