update diagnostics E0282

[liigo]

No description provided.

[rust-highfive]

r? @brson

(rust_highfive has picked a reviewer for you, use r? to override)

[Aatch]

@liigo could you please combine these simple PRs (i.e. this #26876) into a single PR? If you're planning on doing any more similar changes, please make those part of the same PR as well.

[arielb1]

This is badly worded and not-particularly helpful.

[brson]

Thanks @liigo. I also think this isn't as illuminating as it might be - why is the None case so special that it is mentioned explicitly? What is it trying to illustrate - the ::<T> syntax?

[liigo]

@brson Just a hint to the correct syntax of None::<T>, like what compiler sometime says "do you means …" or "try to do …", to help people resolve this compile error. I hint this because I think it's a typical E0282 error, but maybe I'm wrong. Feel free to ignore this pr if it's not helpful.

[Gankra]

I think this has some value -- None can be a pretty common case of this problem in my experience. But it might be too marginal.

[Gankra]

I think it might be sufficient to change the first sentence to something like:

A common form of this error is to use an enum variant that doesn't provide enough information to determine the type of if the overall enum. For instance, None is a valid variant for all Options, and
Ok(0) does not determine the type of Err a Result has.

[liigo]

This just explains why the compile error occurs, but doesn't answer how
to fix that error. So I think it's not enough helpful.
On Jul 27, 2015 10:57 AM, "Alexis Beingessner" notifications@github.com
wrote:

I think it might be sufficient to change the first sentence to something
like:

A common form of this error is to use an enum variant that doesn't provide
enough information to determine the type of if the overall enum. For
instance, None is a valid variant for all Options, and
Ok(0) does not determine the type of Err as Result has.

—
Reply to this email directly or view it on GitHub
#26877 (comment).

[Gankra]

@liigo Yes, I was still intending that you include the example invalid/valid situations. But I suppose you could expand the text.

[liigo]

Closing. This may be addressed out of here in another way.