New rule T0036: Move extension method to dedicated class

[pavel-mikula-sonarsource]

Coding style rule:

Extensions should be in the classes with name that respect the extended type.

public class ISymbolExtensions
{
    public void DoSomething(this IMethodSymbol method) { } // Noncompliant {{Move this extension to IMethodSymbolExtensions class.}}

    public void DoSomething(this ISymbol method) { } // Compliant
}