ArrayPool<T>.Shared.Return does not check if array already returned

[kefyru]

Description

I think it is wrong behaviour.
ArrayPool should throw if we return array which already in pool, otherwise it leads to unpredictable behavior and very difficult error detection

var arr = ArrayPool<byte>.Shared.Rent(8);
ArrayPool<byte>.Shared.Return(arr);
ArrayPool<byte>.Shared.Return(arr);
var arr1 = ArrayPool<byte>.Shared.Rent(8);
var arr2 = ArrayPool<byte>.Shared.Rent(8);
if (ReferenceEquals(arr1, arr2)) throw new Exception(); // throws !!!

Reproduction Steps

see description

Expected behavior

var arr = ArrayPool<byte>.Shared.Rent(8);
ArrayPool<byte>.Shared.Return(arr); // ok
ArrayPool<byte>.Shared.Return(arr); // should throw InvalidArgumentException("array already in pool")

Actual behavior

var arr = ArrayPool<byte>.Shared.Rent(8);
ArrayPool<byte>.Shared.Return(arr); // ok
ArrayPool<byte>.Shared.Return(arr); // ok!!

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

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Issue Details

---

Description

I think it is wrong behaviour.
ArrayPool should throw if we return array which already in pool, otherwise it leads to unpredictable behavior and very difficult error detection

var arr = ArrayPool<byte>.Shared.Rent(8);
ArrayPool<byte>.Shared.Return(arr);
ArrayPool<byte>.Shared.Return(arr);
var arr1 = ArrayPool<byte>.Shared.Rent(8);
var arr2 = ArrayPool<byte>.Shared.Rent(8);
if (ReferenceEquals(arr1, arr2)) throw new Exception(); // throws !!!

Reproduction Steps

see description

Expected behavior

var arr = ArrayPool<byte>.Shared.Rent(8);
ArrayPool<byte>.Shared.Return(arr); // ok
ArrayPool<byte>.Shared.Return(arr); // should throw InvalidArgumentException("array already in pool")

Actual behavior

var arr = ArrayPool<byte>.Shared.Rent(8);
ArrayPool<byte>.Shared.Return(arr); // ok
ArrayPool<byte>.Shared.Return(arr); // ok!!

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

Author:	kefyru
Assignees:	-
Labels:	area-System.Buffers
Milestone:	-

[stephentoub]

Duplicate of #7532

This would be untenably slow by default.