Why can you slice bytes in calldata but not in memory?

Question

If trying to slice bytes in memory one gets the error below. The solidity docs give no explanation just state that array slices are only supported for calldata as of now.

TypeError: Index range access is only supported for dynamic calldata arrays.

Does anyone have a good technical reason for this? Thanks

Answer 1

in solidity the length of an array is stored right before the buffer. since calldata is a different buffer it's simple to just update the offset and length to the calldata, but when the buffer is in memory then the length of the new sliced buffer will overwrite the original buffer.