DiagnosticDescriptor: Support fading out code different from the primary location

[martin-strecker-sonarsource]

Some rules fade out code to indicate unused code:

We use the bool fadeOutCode parameter to make the IDE aware of unused code:

sonar-dotnet/analyzers/src/SonarAnalyzer.Common/DiagnosticAnalyzer/DiagnosticDescriptorFactory.cs

Line 39 in bbd3433

public static DiagnosticDescriptor Create(AnalyzerLanguage language, RuleDescriptor rule, string messageFormat, bool? isEnabledByDefault, bool fadeOutCode) =>

This falls short in cases like above because the code is not just faded out but also squiggled. There is a more flexible way used by Roslyn where the out-fading can be specified separate from the primary location. So in cases like above, we could squiggle the method name and fade out the entire declaration.

These are the rules that fade out code at the moment and may benefit from a more fine grained fadeOutCode behavior.

• S3949 - Calculations should not overflow
• S1144 - Unused private types or members should be removed
• S4487 - Unread "private" fields should be removed
• S2437 - Silly bit operations should not be performed

Original discussion #6679 (comment)