Record structs with InlineArray attribute compares only by the first value.

[Ilchert]

Related to the dotnet/runtime/issues/96943.

Version Used:
dotnet SDK 8.0.204

Steps to Reproduce:

1. Create record struct with InlineArray attribute
2. Call equals.
3. Record structs with InlineArray attribute compares only by the first value.

var a1 = new A();
a1[0]=1;
a1[1]=2;

var a2 = new A();
a2[0] = 1;
a2[1] = 1;


Console.WriteLine(a1.Equals(a2));

[InlineArray(2)]
record struct A
{
   public int P;
}

sharplab

Expected Behavior:
Should compare all values in inline array and print false in this case.

Actual Behavior:
Compares only the first element.

[jaredpar]

This combination of features (record and InlineArray) is not particularly useful. @AlekseyTs did we consider making this combination an error at declaration? Can't see any good reasons to allow this.

[AlekseyTs]

did we consider making this combination an error at declaration? Can't see any good reasons to allow this.

This is an oversight, there was no intent to support record-like behavior for inline arrays.

[lambdageek]

Related runtime issue dotnet/runtime#96943 where we're considering changes to the default behavior of ValueType.Equals for inline arrays

[333fred]

Discussed in LDM on the 17th.

[AlekseyTs]

From https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-06-17.md#conclusion-3:

Applying InlineArrayAttribute to a record struct will be an error.

[AaronRobinsonMSFT]

The runtime is changing the behavior of the default Equals() and GetHashCode() to throw whenever a type is marked with InlineArrayAttribute.

See dotnet/runtime#103612.