Support equality checking on arbitrary types

[cgranade]

Is your feature request related to a problem? Please describe. At the moment, the == operator is not supported for values whose type is given by a type parameter (see screenshot from an IQ# session below). Since all types in Q# are value types, however, we should be able to support == between arbitrary types, including type parameters.

Additional context

[bettinaheim]

Here is roughly the list of things that would need to be done:

• Qubit equality comparison in compiler and runtime
• Array equality comparison in compiler and QArray
• Tuple equality comparison in compiler and QTuple
• UDT equality comparison in compiler and [runtime (UDT class) or code gen]
• Basic callable equality comparison in compiler and runtime
• Partial application equality comparison in runtime

Let me know if you are up for picking some of that up.

[bamarsha]

Since there are good reasons to want to avoid defining equality on callable types, but a generic type parameter 'T could potentially be instantiated as a callable type, it looks like this is blocked by microsoft/qsharp-language#149.

[bamarsha]

However, we could probably add equality comparisons for all of the other concrete types relatively easily (excludes callables and type parameters)... maybe that should be a new issue.

[alan-geller]

I'm going to transfer this issue to the qsharp-language repo, since that's now the proper place for language suggestions.