[Proposal] EqualityComparer should be configurable for record type properties

[SilentViking]

Value based equality check in record types are very useful, however any time a reference type property is introduced, the Equals and GetHashCode methods on the record must be overridden, or an implementation of the reference type must be written with Equals and GetHashCode overrides.

For example, collections are a common issue.

record MyRecord(IEnumerable<string> SomeList, string OtherProperty);

If I want value based equality on SomeList, IEnumerable would need to be wrapped, or MyRecord will need to implement Equals and GetHashCode, losing out on the benefit of compile time generated code which would handle N number of other properties do have desirable default equality comparison.

Proposal:
An attribute, which can be applied to a property, which specifies an IEqualityComparer type with a parameterless constructor.

record MyRecord(
   [property: Comparer<MyIEnumerableComparer<string>>()]
   IEnumerable<string> SomeList, 
    string OtherProperty);

public class MyIEnumerableComparer<T> : IEqualityComparer<IEnumerable<T>>
{
 // ...
}

Then the compile time generated Equals method will create an instance of MyIEnumerableComparer to compare SomeList, and otherwise use EqualityComparer.Default.

[HaloFour]

This could be implemented with a source generators that interprets custom attributes and emits Equals and GetHashCode methods for the record.