RCS1113: Use 'string.IsNullOrEmpty' method is suggested incorrectly

[danielabbatt]

Product and Version Used:
Roslynator 2019 2.9.0 extension

Steps to Reproduce:

with nullable enabled in a c#8.0 project

if (connectedSystem.Credentials.Account == "")

connectedSystem is not nullable

connectedSystem.Credentials is not nullable

connectedSystem.Credentials.Account is string?

Actual Behavior:
The message below is suggested

Message RCS1113 Use 'string.IsNullOrEmpty' method

Expected Behavior:
No suggestion to be made as the intention is to check that connectedSystem.Credentials.Account is not null but is empty. The same suggestion is made when string.Empty is used instead of "".

On looking at the documentation page, the second diagnostic message shows the same behaviour which also appears incorrect.

if (s == "") // RCS1113
{
}

https://github.com/JosefPihrt/Roslynator/blob/master/docs/analyzers/RCS1113.md

I can see this was probably introduced as #650 which incorrectly assumes the intention of whether the original string being null is different to it being empty.

[davidnmbond]

Yes - #650 was a mistake.

[josefpihrt]

@danielabbatt Thanks for the report!