Help here, we should discuss this, @carloscds @viniciushana @ElemarJR.

IMHO:

1. Warning: Code that could/should be improved;
2. Info: Just an alternative way (ex: replacing for with foreach)
3. Error: Clearly a mistake (ex: throwing ArgumentException with an non-existent parameter)

That is it!

For me it's ok.

Agreed, @ElemarJR

Reviewing after talking with the whole group:

1. Info: Just an alternative way (ex: replacing for with foreach). Clearly a matter of opinition. All options are correct.
2. Warning: Code that could/should be improved. It is a code smell and most likely is wrong, but there are situations where the pattern is acceptable or desired.
3. Error: Clearly a mistake (ex: throwing ArgumentException with an non-existent parameter). There is no situation where this code could be correct. There are no differences of opinion.

I am reopening the issue as we need to discuss about the Hidden severity level. Check it out: http://source.roslyn.codeplex.com/#Microsoft.CodeAnalysis/Diagnostic/DiagnosticSeverity.cs,e70281df673d47f6,references

Also, this is Microsoft's description of the severity levels:

1. Hidden: Something that is an issue, as determined by some authority, but is not surfaced through normal means. There may be different mechanisms that act on these issues.
2. Info: Information that does not indicate a problem (i.e. not prescriptive).
3. Warning: Something suspicious but allowed.
4. Error: Something not allowed by the rules of the language or other authority.

What do you think? How do we apply Hidden?