Samuel Tardieu 9eda137008
Rollup merge of #143921 - oli-obk:const-index, r=fee1-dead
Constify `Index` traits

tracking issue: rust-lang/rust#143775

the `SliceIndex` trait cannot be implemented by users as it is sealed. While it would be useful for the `get` method on slices, it seems weird to have a feature gate for that that isn't also gating index syntax at the same time, so I put them under the same feature gate.

r? ```````@fee1-dead```````
2025-07-16 17:06:41 +02:00
..
2025-06-11 15:30:15 +01:00
2025-06-11 15:30:15 +01:00