ReferenceEqualityAnalyzer

This analyzer was designed to identify places within the Ubiquity.NET.Llvm library where the transition away from interning impacts the code base, as well as aid consumers in detecting problems with ambiguity. The transition means any code doing a reference equality check, assuming that all unique instances are interned would get a big surprise as they are no longer guaranteed unique and will fail for things that are really the same. (To handle the problem of unowned "aliasing", which existed in the previous releases as well!). Thus, this analyzer will flag as an error any use of operator == or != that results in reference equality where one of the types involved implements value equality (via IEquatable or IEquatable<T>. This is almost ALWAYS an error in the consuming code. In any case where it isn't the code should be converted to use an explicit call to object.ReferenceEquals() so that it is explicitly clear what the intent is.

IDs

Rule ID	Category	Severity	Notes
UNL000	Internal	Error	Diagnostics
UNL001	Usage	Error	Diagnostics

UNL000

An internal error (exception) was detected in the analyzer itself. This is unlikely to occur but any occurrences of this are an error in the analyzer itself that should be reported (and fixed) as a bug.

UNL001

Reference equality was inferred but value equality is available. This is an indication of some part of the code base that has not properly transitioned or new code that is implemented incorrectly. If, and ONLY if, reference equality is actually intended then the call-site should use object.ReferenceEquals() and add an explanatory comment.