Non-alloc enumerables for Unity structures and C# IList/IReadOnlyList interfaces.

• Transform: default children enumerator allocates the enumerator object. Use the idiom foreach (Transform t in transform.EnumerateNonAlloc()) to use a non-alloc enumerable instead.
• Input.touches: calling Input.touches allocates the array of touches each time you call it. Use the idiom foreach (Touch t in InputTouches.EnumerateNonAlloc()) to use a non-alloc enumerable instead.
• Input.accelerationEvents: calling Input.accelerationEvents allocates the array of acceleration events each time you call it. Use the idiom foreach (AccelerationEvent a in InputAccelerationEvents.EnumerateNonAlloc()) to use a non-alloc enumerable instead.
• (Unity 2021+ only) GameObject and Component: use the extension methods EnumerateComponents, EnumerateComponentsInChildren and EnumerateComponentsInParent to enumerate components using pooled lists. Heap memory may be allocated if there are no pooled lists available or if the pooled list isn't big enough to hold all values, but overall repeated calls will end up being non-alloc.
• (Unity 2021+ only) Renderer: use the extension methods EnumerateMaterials, EnumerateSharedMaterials and EnumerateClosestReflectionProbes to enumerate materials and reflection probe info from a renderer using pooled lists. The same caveats from enumerating components mentioned above apply.
• Rect: use the idiom foreach (Vector2 corner in rect.EnumerateCorners()) to enumerate a Rect's 4 corners.
• Bounds: use the idiom foreach (Vector3 corner in bounds.EnumerateCorners()) to enumerate a Bounds' 8 corners.

By default, all built-in generic arrays and container classes like List<>, Dictionary<,> and HashSet<,> return struct enumerators when used in foreach blocks, so there are no "EnumerateNonAlloc" for them.

In case you are using IList<> and IReadOnlyList<> interfaces directly, though, the enumerator used in foreach blocks get boxed and allocate heap memory. Use the idiom foreach (var value in someIListOrIReadOnlyList.EnumerateNonAlloc()) to use a non-alloc enumerable instead.