Merkle Proof gas cost may be reduced in some cases.

[Cr0wn-Gh0ul]

openzeppelin-contracts/contracts/utils/cryptography/MerkleProof.sol

Line 28 in eae2384

bytes32[] memory proof,

In the normal mode of operation a Merkle proof is passed into a contract by a external party. As such there is little benefit to copying the Merkle proof to memory before invoking _efficientHash. Therefore gas may be saved if in this case calldata is used instead of memory for the proof variable. Recommend either modifying the contract or offering a variant that utilizes calldata.

[frangio]

This is true. Feel free to send a PR.

Does Solidity allow functions of the same name where one has storage pointer argument and the other calldata pointer argument?

[BCLeFevre]

Looks like the original contract was written before 0.6.9 which allowed for using calldata within internal function calls. Most likely why memory is still being used in it's current iteration.

[Cr0wn-Gh0ul]

@frangio Created a PR with this change. #3200